Five Reasons Why it’s Okay to Love Oxalis

This is an updated reprint of a May 2015 article. As of 2023, eight years later, Natural Areas (now called “Natural Resource Areas”) are still being sprayed with powerful pesticides against oxalis. It’s still futile.


Five Reasons it’s Okay to Love Oxalis – and Stop Poisoning It

(May 11, 2015; updated March 8, 2023)

The oxalis season is over, and the perky yellow flowers have vanished for another year. These Bermuda buttercups will be back next year to herald the spring, bringing joy to those who love them, irritation to those who hate them, and powerful herbicides targeted at them in San Francisco’s so-called “Natural” Areas.

oxalis in glen canyon feb 2011


These flowers are so visible in spring that Bay Nature magazine did an article about them in March 2015: A Natural History of the Little Yellow Flower that’s Everywhere Right Now. It quoted Jake Sigg, the retired SF Recreation and Parks gardener who is considered the doyen of San Francisco’s native plant movement. He hates oxalis pes caprae, which he considers extremely invasive. The article quotes him as saying that, without intervention, “in X many years Twin Peaks would just be one solid mass of yellow, and there wouldn’t be any other plants there…” The article suggested that an oxalis-dominated landscape “drives away coyotes, hawks and owls that feed on grassland foragers, and the situation is especially dire for endangered Mission blue butterflies, which depend heavily on native wildflowers.” Most of those ‘facts’ about oxalis are mistaken as we’ll explain below.

Mr Sigg’s theories align with those of the Natural Resources Department (NRD) of the San Francisco Recreation and Parks Department (SFRPD), which uses the herbicide triclopyr (among others) to battle oxalis  despite its dubious efficacy for the purpose.

Close-up - Pesticide notice Triclopyr - Glen Canyon - Jan 2023 -Crags Court entrance midway down stairs

Pesticide notice Triclopyr – Glen Canyon – Jan 2023: Triclopyr on oxalis, sheep sorrel, plantain

An article on, based on a detailed study by the Marin Municipal Water Department, describes some of the issues with triclopyr (with the brand name Garlon):

  • It “causes severe birth defects in rats at relatively low levels of exposure.” Baby rats were born with brains outside their skulls, or no eyelids. Exposed adult females rats also had more failed pregnancies.
  •   Rat and dog studies showed damage to the kidneys, the liver, and the blood.
  •   About 1-2% of the pesticide falling on human skin is absorbed within a day. For rodents, its absorbed twelve times as fast. It’s unclear what happens to predators such as hawks that eat the affected rodents.
  • Dogs  may be particularly vulnerable; their kidneys may not be able to handle triclopyr as well as rats or humans.  Dow Chemical objected when the Environmental Protection agency noted decreased red-dye excretion as an adverse effect, so now it’s just listed as an “effect.”
  •  It very probably alters soil biology. “Garlon 4 can inhibit growth in the mycorrhizal fungi…” ( soil funguses that help plant nutrition.)
  •  It’s particularly dangerous to aquatic creatures: fish (particularly salmon); invertebrates; and aquatic plants.
  • It can persist in dead vegetation for up to two years.
twin peaks - jan 2015 - imazapyr and garlon for poison oak cotoneaster oxalis

Natural Areas Program uses triclopyr on oxalis – Jan 2015

First, a little about the actual natural history of oxalis. This plant doesn’t set seed in California, and spreads entirely by sending out roots and forming little bulbils (like tiny potatoes) underground. It’s usually found where the soil has been disturbed by activities such as road-building, gardening, or trail-building. In some cases, the disturbance come from landslides or something similar. It can’t stand frost. If we do nothing,  it would tend to die down rather than spreading uncontrollably.

In disturbed landscapes, it can spread fast. For this reason it can be a nuisance in gardens. People don’t want to leave their gardens alone for years to let nature take its course with the oxalis, and not every garden design includes brilliant yellow as the dominant color for a few weeks. The only way to eradicate it in the short term is to dig it out carefully every time you see it, and make sure you get most of the bulbils. Or use strong herbicides, which may not work.

In a natural landscape, though, it’s a different story and here’s why.


Oxalis is actually an excellent plant for bees and butterflies.  When blooming, it provides “copious nectar.” In fact, it generously gives away its nectar. Since it doesn’t set seed, it doesn’t benefit from pollinators – but it’s a food source for honey bees, bumblebees and butterflies. (You can read a rather technical description of the plant in a 2-page PDF note from UCLA’s Barry A. Prigge and Arthur C. Gibson.: oxalis_pes-caprae_ucla_santamonicas )

In fact, a 2014 study  shows that plant communities with exotic plants had more plant species as well as more pollinators, that pollinators didn’t prefer native plants, and that even some specialist pollinators depended on introduced plant species. [ Journal of Ecology – 2014 – Stouffer Cirtwill & Bascompte – How exotic plants integrate into pollination networks ]

It’s true the Mission Blue butterfly needs (native) lupine as its nursery plant. (It doesn’t depend on any other native wildflowers – only three varieties of lupine.  Incidentally, one of the key nectar sources for the Mission Blue butterfly is an invasive non-native Italian thistle: Carduus pycnocephalus).

Lupine has been planted on Twin Peaks as NAP attempts to reintroduce the Mission Blue butterfly there. But lupine is also a plant of disturbed areas, which means that NAP must maintain it or it will die out as the area stabilizes. They have to keep planting it, weeding, and trimming the grass around the lupine patches to make it attractive to the butterfly. An SFRPD report on the reintroduction project said “unmanaged habitat deteriorates quickly.” Presumably, they don’t use pesticides near the lupine patches, since it would likely kill that too. Despite what is implied in the Bay Nature article, it’s not oxalis that’s the issue. The real problem is another native plant, the coyote bush which takes over grasslands in a natural succession.


Oxalis bulbils are a food source for wildlife. Gophers and other rodents eat them. In fact, the Bay Nature article says, “Their spread is abetted by pocket gophers and scrub jays, which have been spotted carrying the bulbs and caching them in the ground—effectively planting them in new areas.”

Since gophers are a foundation species in the food web, being dinner for predators from hawks to coyotes to great blue herons, these plants actually provide habitat benefits whether or not they’re flowering, because the bulbils are there all year.

gopher-twin-peaksWhere there are gophers, the predators follow. Like the coyotes in these pictures, which clearly haven’t been driven away by a landscape dominated by oxalis.

coyote pouncing in oxalis field - copyright Janet Kessler

coyote pouncing in oxalis field – copyright Janet Kessler

coyote in oxalis field - copyright Janet Kessler

coyote in oxalis field – copyright Janet Kessler


The article says that oxalis leaves “bare ground during the six months of the year oxalis doesn’t flower.” That’s not true either.

oxalis interspersed with grasses and other plants

oxalis in glen canyon feb 2011The spectacular yellow bloom of the oxalis – valuable because it the mass of color attracts honey bees and bumblebees – gives the impression that it’s the only plant there.  But though it visually takes over the landscape when it’s in bloom, it naturally grows interspersed with grasses and other plants. Like in the picture above.

In fact, oxalis tends to enrich the soil with phosphorus, which is good for grass.

So when it finishes blooming, as it has by now – you don’t get bare ground. The picture below shows the same area as the first picture in this article – but it’s after the oxalis bloom is over. It’s a grassland.

glen canyon after the oxalis season


One argument – related  to the ‘bare ground’ argument – is that oxalis takes over grasslands and destroys them, particularly the native grasses. However, grasslands in most of California including San Francisco are dominated non-native grasses. The change occurred over 100 years ago, when these grasses were planted for pasture. So the grassland that NRD is defending with herbicides are primarily non-native anyway.

oxalis and california poppies sm But anyway, what’s the evidence that oxalis is actually damaging native plants?

It’s true some European studies do suggest that an increase in oxalis is associated with a decrease in native plants diversity -though whether it’s a cause is unclear. It may just be benefiting from human activities that disrupt the landscape. Another study put oxalis head-to-head with a native annual grass, lolium rigidum. The native grass tended to dominate. Their conclusion: “Oxalis is a poor competitor. This is consistent with the preferential distribution of Oxalis in disturbed areas such as ruderal habitats, and might explain its low influence on the cover of native species in invaded sites.

The California Invasive Plant Council rates its invasiveness as “moderate,” considering it as somewhat invasive in sand dunes and less so in coastal bluff areas.

In San Francisco, every place where oxalis grows is already a disturbed environment, a mix of non-native grasses and plants with native plants (some of which have been artificially planted).  Here,  oxalis appears to grow happily with other plants – including, for instance, the native California poppy in the picture above.


Children love oxalis, both for its pretty flower and for the sour taste of its edible stems.

Even small children love gathering posies of Bermuda buttercups (though picking flowers is technically prohibited in Natural Areas). The flowers are surprisingly hardy for wildflowers, and in a glass of water last quite well as cut-flowers.

The plant is edible, and its tart leaves make a nice addition to salad. People enjoy snacking on its sour stems. Besides Bermuda buttercup, it’s also called ‘sourgrass’ and ‘soursob.’ It does contain oxalic acid (as does spinach, for instance), and so you probably wouldn’t want to make a meal of it. Though in South Africa it’s made into soup.

Adding pesticides to it is probably a bad thing.

Photo credit: Badjonni (Creative Commons - Flickr)

Photo credit: Badjonni (Creative Commons – Flickr)


From our current evidence, there’s no sign that oxalis has a negative impact on wildlife, and plenty of evidence it’s already part of the ecological food web of our city.  The evidence also suggests it’s not having a negative effect on other plants in San Francisco either. Lots of people find this flower attractive; one writer described it as the city smiling with Bermuda buttercups.

In any case, even Doug Johnson of the California Invasive Plant Council doesn’t think it’s worth attacking at a landscape level: the payoff isn’t worth the expense. Removing it from the hundreds of acres in Natural Areas isn’t as simple as eradicating it from a small yard where it’s clashing with the garden design. It requires a lot of work, a lot of powerful herbicides, a multi-year effort – and for what?

The justification for using strong pesticides to control it is weak. We call on NAP to stop using Tier I and Tier II herbicides altogether.

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Oxalis and the Herbicide “solution”

This article is republished with permission from Conservation Sense and Nonsense, an environmental blog focused on the San Francisco Bay Area.



As a long-time reader of Jake Sigg’s Nature News, I am very familiar with his passionate crusade against Oxalis pes-caprae.  When oxalis appears in the landscape in January, Jake gears up his campaign again. This year the Westside Observer published an article by Jake about oxalis that reaches a new level of urgency and asks land managers to increase their use of herbicides to kill the plant.

In the past, Jake has advised careful and relentless hand-pulling of oxalis with its bulb intact.  Now he acknowledges that hand-pulling is useless to eradicate oxalis.  Although herbicides have been used on oxalis in San Francisco’s parks for 25 years, Jake now wants MORE herbicides to be used. Over 20% of all herbicide spraying by the Natural Resources Division (NRD) of the Recreation and Park Department was applied to kill oxalis in “natural areas” in 2022. NRD sprayed oxalis 35 times in 2021 and 38 times in 2022.

Spraying Garlon on Twin Peaks in San Francisco, February 2011

From January to March, virtually all the herbicides sprayed by NRD in the so-called “natural areas” were sprayed on oxalis.  If it were possible to eradicate oxalis with herbicide, why is there more oxalis now than there was 25 years ago, when NRD (then known as the Natural Areas Program) started spraying herbicides in the “natural areas?”  A lot of herbicide has flowed under the bridge in the past 25 years, but oxalis thrives. What is the point of pouring more herbicide under the bridge of sighs?  We’re pouring more fuel on the fire with nothing to show for it.

Pesticide notice - Path between Christopher Park and Glen Canyon - Jan 30 2023

One of many pesticide application notices on oxalis in Glen Canyon Park in February 2023.

The University of California Integrated Pest Management Program explains why it’s not possible to eradicate Oxalis pes-caprae with herbicides: “Several postemergent herbicides including triclopyr and fluroxypyr (selective for broadleaf plants) and glyphosate and glufosinate (nonselective) effectively kill the top growth of this weed but are harmful to most ornamentals, so be careful these herbicides don’t drift onto desirable plants. These herbicides don’t kill the bulbs, and regrowth from bulbs should be expected.” In other words, you can kill the above-ground top growth and other non-target plants in the vicinity, but you won’t kill the oxalis. 

Chemical Warfare?

On one hand, Jake urges public land managers to escalate chemical warfare against oxalis.  On the other hand, he accuses oxalis of “chemical warfare” (AKA allelopathy), secreting chemicals that kill other plants. This accusation is pure speculation on Jake’s part.  He offers as “evidence” of his speculation that after oxalis dies back in April “we’re left with bare ground for the rest of summer and autumn.”  He ignores the obvious fact that annual spraying of gallons of herbicide on oxalis in the “natural areas” could be causing the bare ground. It has apparently not occurred to him that many herbicides are non-selective, killing everything they touch, not just targeted plants. And those herbicides that claim to be selective are very mobile in the soil, capable of killing adjacent plants through their roots.  If you don’t want to see bare ground, don’t spray herbicides!

Jake asks for more research on how oxalis interacts with other plants in his article published by Westside Observer. He is apparently unaware of the research that has been done by scientists at University of Montana to address the question of how competitive oxalis is in plant communities that include native plants:  “Oxalis is a poor competitor. This is consistent with the preferential distribution of Oxalis in disturbed areas such as ruderal habitats, and might explain its low influence on the cover of native species in invaded sites.

The study explains why oxalis does not suppress the growth of other plants, including natives.  Oxalis makes more phosphorous available in the soil, which essentially acts as a fertilizer for other plants“These results are consistent with our field data and suggest that Oxalis may improve P availability in the field.”

This study was published in 2007.  It found that Oxalis pes-caprae does not suppress the growth of other plants and, in fact, increases nutrients in the soil.  Jake apparently doesn’t know about this study and related studies that found that pollinators are as interested in O. pes-caprae as they are in native plants.

Jake’s accusation that oxalis is waging “chemical warfare” against native plants does not come out of nowhere.  The same accusation was used against eucalyptus trees for decades until a definitive empirical study proved that eucalyptus is not allelopathic.  The California Invasive Plant Council removed that accusation from its evaluation of Blue Gum eucalyptus in 2015 (along with the accusation that eucalyptus kills birds).  As the readers of Jake’s Nature News know, his hatred of eucalyptus is second only to his hatred of oxalis.  There was never evidence that eucalyptus is allelopathic and there is no evidence that oxalis is allelopathic.

Does biodiversity justify poisoning nature?

Jake justifies his crusade against oxalis based on his belief that its existence threatens biodiversity.  Since there is no evidence that oxalis kills other plants, there is no reason to believe its existence threatens biodiversity.  

Jake also asks us to include only native plants in the measure of biodiversity, but he is alone in that belief.  Scientific measurements of biodiversity include all species of plants and animals, whether considered native or non-native.  The Recreation and Open Space Element of San Francisco’s General Plan explicitly acknowledges that both native and non-native plants contribute to biodiversity:  “Parks and open spaces in San Francisco include both native and non-native species, both of which can contribute to local biodiversity.” (Policy 4.1, Recreation and Open Space of San Francisco General Plan)

Jake ups the ante against oxalis by claiming that wildlife requires solely native plants, a fundamental tenet in native plant ideology.  Again, this claim is unsupported by evidence.  As Professor Art Shapiro (UC Davis) says in his Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, “Most California natives in cultivation are of no more butterfly interest than nonnatives, and most of the best butterfly flowers in our area are exotic.”

coyote hunting in oxalis field. Copyright Janet Kessler

On one hand, Jake claims that oxalis deprives birds and other foragers of food.  On the other hand, Jake acknowledges that oxalis is foraged by gophers and scrub jays (based on one observation).  Jake wants it both ways because that serves his purpose. 

If native plants were any benefit to wildlife, that benefit is quashed by the widespread use of herbicides being used in the “natural areas.”  For example, Himalayan blackberries are an important source of food for birds and other wildlife in San Francisco’s parks and are also eaten by children visiting the parks.  The blackberries are routinely sprayed with herbicides in the so-called “natural areas.”  Wildlife is exposed to the herbicides and they are also deprived of important sources of food.

A recent survey of 24,000 gardens in the UK found that pesticide use had a significant effect on bird life. The study found that gardens that used pesticides had fewer species of birds than similar gardens that did not use pesticides:

“Pesticide spraying impacted the positive effect [surrounding habitat quality] had on bird richness. Specifically, ‘species richness [number of species] increases with the surrounding quality, both for gardens that do not use pesticides and for gardens that applied pesticides, but this effect is significantly less strong when pesticides are applied’ the study indicates. Scientists zeroed in on three active ingredients: the weed killer glyphosate, the neonicotinoid insecticide acetamiprid, and the synthetic pyrethroid deltamethrin as resulting in the most damaging pesticide impacts to bird species’ richness.” Note that the study’s definition of “surrounding habitat quality” made no distinction between native and non-native plants.  The British are not strong supporters of native plant ideology.

Nativists keep using huge quantities of herbicide to kill vegetation they don’t like, while also claiming that their eradication projects benefit birds. This is a fundamental contradiction. Their eradication projects are harmful to birds and other creatures that live in our parks and open spaces.

Jake’s Lament

In his article, Jake laments that people are accepting changes in the landscape because they don’t remember what the landscape looked like 100 years ago.  His “baseline view” of what landscapes should look like is much further in the past than most people’s memories of the landscape.

The climate has changed significantly in the past 100 years.  When the climate changes vegetation changes.  We should welcome the changes because they are required for the survival of any landscape.  When the climate changes, plants and animals must move, adapt, or die.  The changing landscape is an indication that plants are adapting to changing conditions. 

We cannot stop evolution, nor should we try.  Herbicides are a futile attempt to stop evolution.  Herbicides cannot stop evolution, because plants evolve a resistance to them.  After 25 years of constant herbicide use in San Francisco’s parks and open spaces, we should assume that they are less effective every year.

While San Francisco’s Recreation and Park Department has significantly reduced its use of herbicides since 2010, the Natural Resources Division that is responsible for the “natural areas” has not. Natural Resources Division is now using more herbicides than the rest of the parks.  Source: San Francisco IPM Program, Department of Environment

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Toxic Pesticides in Glen Canyon Park

It’s pesticide season in Glen Canyon Park, with one of the most toxic pesticides in use: Triclopyr. (This is the one that’s brand-named Vastlan.) The target plants are oxalis, as usual! And a new one – Sheep Sorrel. It’s actually an edible plant, sometimes sold in farmers’ markets. Said one of our readers, “You can make a good soup (green borscht) from sheep sorrel – with green onions. Possibly adding spinach and potatoes. (There might be other variations.) One vendor at the Alemany Farmers Market sells sheep sorrel.”

We cannot recommend harvesting sheep sorrel that’s been sprayed with triclopyr!

These pictures were sent to us by a supporter. “FIVE signs in Glen Canyon — there might have been more, but this is what I saw — all in that center part of the park. Here are two photos of each: one distant, and one so you can read the details.”

Pesticide notice – Path between Christopher Park and Glen Canyon

Pesticide notice - Path between Christopher Park and Glen Canyon - Jan 30 2023

Closeup of pesticide notice Pesticide notice – Path between Christopher Park and Glen Canyon

Pesticide notice - Amber Street Entrance at base of stairs - Jan 30 2023

Pesticide notice – Amber Street Entrance at base of stairs – Jan 30 2023

Close-up - Pesticide notice - Amber Street Entrance at base of stairs - Jan 30 2023

Close-up – Pesticide notice – Amber Street Entrance at base of stairs – Jan 30 2023

Pesticide notices - Glen Canyon - Jan 2023 - On the boardwalk

Pesticides – Glen Canyon – Jan 2023 – On the boardwalk

Close-up of Pesticides notice - Glen Canyon - Jan 2023 - Pesticide notice in Glen Canyon - On the boardwalk

Close-up – Pesticides – Glen Canyon – Jan 2023 – Pesticide notice in Glen Canyon – On the boardwalk

Pesticide triclopyr - Glen Canyon - Jan 2023 - Across from Nursery School

Pesticide triclopyr – Glen Canyon – Jan 2023 – Across from Nursery School

Close-up -Pesticide notice for triclopyr - Glen Canyon - Jan 2023 - Across from Nursery School

Close-up -Pesticide notice for triclopyr – Glen Canyon – Jan 2023 – Across from Nursery School

Pesticide notice Triclopyr - Glen Canyon - Jan 2023 -Crags Court entrance midway down stairs

Pesticide notice Triclopyr – Glen Canyon – Jan 2023 -Crags Court entrance midway down stairs

Close-up - Pesticide notice Triclopyr - Glen Canyon - Jan 2023 -Crags Court entrance midway down stairs

Close-up – Pesticide notice Triclopyr – Glen Canyon – Jan 2023 -Crags Court entrance midway down stairs

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Season’s Greetings and Happy New Year!

The San Francisco Forest Alliance,  a 501(c)4 not-for-profit organization with a mission of inclusive environmentalism, continues our campaign to protect our environment through outreach and providing information. As we near the end of 2022, we reflect that it’s been 11 years.

We oppose the unnecessary destruction of trees, oppose the use of toxic herbicides in parks and public lands, and support public access to our parks and conservation of our tree canopy. We stand for transparency in the use of public funds.

We wish all our supporters Season’s Greetings and a hopeful year in 2023!

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The Forest on Albany Hill

One of the blogs we follow, Conservation Sense and Nonsense, is trying to prevent the destruction of the eucalyptus forest on Albany Hill. This stand of trees sequesters carbon, cleans the air near a heavily trafficked road – and provides a wintering ground for Monarch butterflies.

Conservation Sense and Nonsense has published a three-part response, in the form of a letter to the relevant authority, The Albany City Council.

The first segment explains why it is not necessary to destroy the forest.  The second segment will explain the consequences of destroying the forest.  The final segment will explain why it is unlikely that the forest can be replaced by native trees.”


Though the eucalyptus trees on Albany Hill are showing signs of drought stress, so are *all* trees in the area. The eucalyptus are most likely to recover, being much more drought-adapted.

Read the detailed article:

Epicormic growth is a eucalyptus defense mechanism allowing the tree to recover from drought


The second article spells out the consequences:

“The premature destruction of the eucalyptus forest will have many negative consequences:

  • The loss of significant amounts of fog drip from the tall trees. [Note This reduces the amount of moisture in the area, affecting vegetation and fire risk]
  • The creation of tons of wood debris that will contribute to fire hazards
  • The regrowth of the trees into unstable multi-stemmed trees with lower fire ladders
  • The loss of habitat for overwintering monarch butterflies” [Note: Monarchs strongly prefer eucalyptus for winter roosts.]

Monarch butterflies roosting on Albany Hill eucalyptus. Photo: Conservation Sense and Nonsense

Read the detailed article:


The Albany City Council hopes to replace the eucalyptus with “native” trees. The third article explains why this is not going to happen, particularly since there are no plans to irrigate the newly-planted area.

“Somehow, this diverse, drought-tolerant, fire-resilient, tall, native (with droughty eucalyptus species?) forest is expected to survive without irrigation:  “If drought-tolerant tree species are planted as seedlings, in the fall with sufficient planting site preparation and adequate rain fall, minimal if any irrigation will be required.” (5)  When predicting the fate of the existing eucalyptus forest, the plans assume that the drought will continue.  When predicting the fate of a replacement forest, the plans assume that the drought will end.”

It goes on to say: “Historically, areas on Albany Hill that are now forested with eucalyptus were treeless because native trees are not adapted to the challenging climate conditions.  If the eucalyptus forest on Albany Hill is destroyed, Albany Hill is likely to be treeless again.”

The Monarch butterflies will be out of luck. So will native vegetation that depends on the wind protection and moisture the forest provides. So will be all tree-lovers that have admired and enjoyed this little urban forest.

Read the details:

If this account moves you to help, please write to:
Albany City Council, 1000 San Pablo Ave,  Albany, CA 94707

Albany Hill. By Clarkiarubicunda – Own work, CC BY-SA 4.0 – Wikimedia

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A tree ponders life upon waking

Someone sent us this charming, incisive, bitter-sweet graphic about a eucalyptus tree. The artist, Charlotte Hildebrand, kindly gave us permission to reproduce it here.

Graphic of a eucalyptus tree 125 years old and home to 1000 birds pondering life

This tree, such an important part of the ecosystem – a shelter for birds, a splendid carbon sink, a catcher of fog, ponders its purpose in life. Like the trees on Mt Sutro and Mt Davidson, it’s 125 years old.

Thank you, Charlotte Hildebrand.

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Pesticide Usage in 2021: SFRPD Does Better – except for NRD

As we usually do, we compiled the pesticide usage data for San Francisco Recreation and Parks Department for 2021.  (We exclude Harding Park – but not the other golf courses – from this analysis because it’s externally-managed under a PGA contract to be kept tournament-ready at all times.) We’re pleased to note that SFRPD has reduced its pesticide usage in comparison to 2020 and 2019. 


But this is not true of the Natural Resources Division (this includes PUC areas managed in the same way – i.e. use of toxic herbicides against plants they dislike). Their usage has risen and is the highest it’s ever been from 2016.

The Natural Resources Department (NRD, formerly the Natural Areas Program or NAP) is the entity that in trying to bring “native” plants to more than a thousand acres of our parks, cuts down trees and restrict access to people and their pets.  NRD, which accounts for perhaps a fourth of the land area, used over 70% of the pesticides measured as active ingredients in fluid ounces.

NRD – and PUC lands that they are managing the same way – continued to increase their use of triclopyr since the new pesticide Vastlan has been designated Tier II (More Hazardous) instead of Garlon, which was Tier I (Most Hazardous). In both herbicides, the active ingredient is triclopyr. They also increased their usage of imazapyr, and continued to use Roundup, though in smaller quantities than before.

Here are the two earlier graphs lined up to show the comparison. The Native Plant areas used more herbicides in 2021 than they had ever used in the last six years – or that the other SFRPD departments together used in the same timeframe. Their failure to reduce usage in 2021 is in stark contrast to the more than 50% drop in the other SFRPD.

SFRPD Other (i.e. other than the Native plant areas) uses mainly Polaris (imazapyr) and Clearcast ( ammonium salt of imazamox). The native plant areas, NRD / SFPUC, use large amounts of triclopyr, (Garlon and Vastlan), as well as some glyphosate (Roundup).


The NRD’s continually growing usage of the herbicides is a sign that this strategy is failing. They have been using hazardous chemicals on some 50 target species of plants year after year. Theoretically, the point of using toxic herbicides on unwanted species is to allow the desired species to replace them.  Instead, the growing usage of these chemicals shows that if anything, the situation is only made worse.

This stands to reason; “invasive” plants are successful because they are better adapted to current conditions. If they are destroyed with herbicides, the replacement is likely to be the next best adapted (thus, invasive) species. Given 50 target species, the bench is deep. This leads to a vicious cycle of hazardous herbicide use, clearly visible in the graph above.


For many years since we started compiling these data, Sharp Park has been off-limits for pesticides. We’ve seen very minimal usage – maybe 3 or 4 times over all the years. It’s home to the red-legged frog, and the San Francisco garter snake.

In 2021, that changed. In the space of one year, pesticides were applied 9 times. We did anticipate this would happen as NRD extended its grip on this park.


San Francisco’s Department of the Environment (SFEnvironment) assigns Tier hazard ratings to the various pesticides it uses. Tier III is Least Hazardous, Tier II is More Hazardous, and Tier I is Most Hazardous.  Over the years we have been following this usage, we have seen various chemicals being moved from one Tier to another. Milestone was moved from Tier I to Tier II; Glyphosate (Roundup, Aquamaster)  from Tier II to Tier I; and triclopyr (Garlon, Garlon 4 Ultra, Turflon, Vastlan) from Tier I to Tier II (for Vastlan and Turflon). Avenger was moved from Tier II to Tier III, which we think makes sense and makes analysis easier. We analyze the usage of Tier I and Tier II herbicides.


SF Forest Alliance has been trying to encourage SFRPD to reduce or eliminate Tier I and Tier II herbicide use. Some years ago, it appeared that pesticide usage was declining, especially after the Roundup revelations. When we wrote our Pesticides report for 2016, the other areas of SFRPD had slashed their herbicide use; the NRD accounted for 74% of pesticide usage. The 2021 data have renewed our hope that SFRPD’s other departments will adopt a cautious approach to the use of toxic herbicides. Unfortunately, this does not appear true of the nativist departments, NRD / PUC.

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McLaren Park Loses More Trees

From Lance Mellon:

“This nativism is a strange phenomenon. I see every day, next to my community garden at Mclaren Park, the devastation caused when they cut down those beautiful woods to install their native garden. It is an unforgivable act of ignorance and destruction.”


Picture of beautiful trees destroyed to create a "native" garden

Beautiful trees at McLaren Park – copyright Lance Mellon

Beautiful trees destroyed to create a "Native" garden

Stately beautiful tree at McLaren Park – copyright Lance Mellon


Native garden – copyright Lance Mellon

Native garden 2 – copyright Lance Mellon

“This needs to be curtailed before all the trees are gone. The largest tree in those woods was a 100+-year-old Monterey Cypress that housed innumerable owls, crows, and a myriad of flora and fauna.”

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Good news: Tree Felling Plan in Napa Stops

In recent weeks, we heard of another project to cut down eucalyptus trees, despite the negative impact on climate change, wildlife, and neighborhoods. And today, we were pleased to learn that it had been reversed!

Someone wrote to us to say “… on the river in Napa where a lot of eucalyptus trees that have been here some over 50 years are scheduled to all be cut down. These trees are homes to owls, ravens, night herons, egrets and more.  Can you please help us to save the trees and wildlife that will be displaced?

We wrote back to describe our experience. Perhaps it was helpful, perhaps there were other reasons for the project being stopped. But today we were really happy to get this letter:

“Great News from the CDFW -they have decided to halt the assault on our trees along the Napa River on Milton Road!  I wanted to thank you for your support and suggestions and if I can help your organization, please let me know.

This will be good both for the human neighbors, and the local wildlife.

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Still More Trees Cut Down in Sutro Forest – March 2022

The article below is essentially a sequel to the previous one. More Trees Being Cut Down in Sutro Forest  and is also republished with permission from


As readers of this site will know, a lot of trees are being felled in the portion of the forest closest to the hospital. One forest-lover wrote to us about it. That part is HERE.

A few days later, they wrote “The hillside now looks like an Oregon clearcut. I didn’t have a chance to take a pic today but at this point it’s like morbidly photographing a corpse at a funeral.


Here’s some photographs of the area from 2013, (from Tony Holiday’s blog, Stairways are Heaven,  and used with permission). The dense woods at the top right of the picture is what’s being felled now.


And here’s what’s happening now.

This is the staircase, from below – without its forest.

The chosen area for destruction is adjacent to the Parnassus campus and near the hospital that is to be substantially rebuilt and expanded. It’s an ugly thing to watch.

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More Trees Being Cut Down in Sutro Forest

This article has been republished from with permission and updates.

“Can you tell me what’s happening on the north side of the forest? I’ve been watching them cut down a swath from a lunchroom at UCSF the last few days,” said an email to us a day ago.

Yes. It’s a continuation of the “Vegetation Management Plan” that we have been trying to oppose for over a decade, and which will result in an estimated 10,000 trees being cut down. Coincidentally, this recent action is close to the planned new (rebuilt) hospital at Parnassus.

It looks like they’re clearing for a road,” said a shocked follow-up email. Then we received this photograph, taken from the hospital. “A week ago you couldn’t see the houses up top. Men chainsaw the trees and the machine in the upper right clears the land. You have my permission to republish this as you see fit.”

This is what the forest looked like, back before they started the massive tree removals.

Group of people walking a trail through beautiful dense Sutro Forest in 2007

Mt Sutro Forest in 2007


UCSF recently sent out a notice that we reprint here for information to anyone who might not have seen it:

Tree Removal Along Medical Center Way

Starting February 15th through mid-March, there will be active tree work along Medical Center Way near Edgewood Avenue and Farnsworth Lane due to upcoming tree removal as prescribed in the Vegetation Management Plan.

To ensure the safety of tree workers, neighbors, staff, and visitors there will be no access to the Reserve via Farnsworth Lane and Edgewood Avenue. Chain-link fencing will be placed along the property line up to the Surge Parking Lot, and Medical Center Way will be closed.

Potential Impacts:
Intermittent loud noises from tree felling and wood chipping.
A crane will be placed in the Surge Parking Lot to assist with the tree removal.
Work will occur within normal business hours. No weekend work is anticipated at this time.

Please obey all instructions from tree workers and signage by not entering the work area.

See below for a map detailing the area. The blue rectangle outlines the approximate area of tree work, and the orange line shows where fencing will be placed as a safety precaution.

We apologize for any inconvenience this work may cause, and we appreciate your patience.


Meanwhile, aside from the loss of the trees, the “removal” is also taking place just as the nesting season is under way.  Wildcare, the not-for-profit that rehabilitates wild birds and animals – including a lot of babies – sent out a message: “RESPECT THE NEST! BABY HUMMINGBIRDS ARE HERE!

They tell us that apparently abandoned hummingbird nests are not actually abandoned, but that human activity close by may discourage feeding. And the also point out:

Don’t panic, those baby hummingbirds are most likely not orphaned, but their presence DOES mean it is no longer safe to prune or trim trees, bushes or shrubs! Wildlife Baby Season has begun!”

We don’t suppose UCSF is listening, since their plans for tree felling run through mid-March. Even though we know that hummingbirds nest in Sutro Forest.

Two tiny hummingbird nests collected from Sutro Forest after the nesting season

Hummingbird nests collected in Sutro Forest after the nesting season

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Herbicide Time – Triclopyr in Glen Canyon

It’s January, and San Francisco is brightened by the yellow oxalis springing up on green hillsides. Less bright, though, is the usual Blights of Spring – herbicides applied in our parks where our kids and pups play.

Here’s an idyllic scene in Glen Canyon – a beautiful trail, the grass dotted with yellow spring flowers. Not so idyllic: toxic herbicides are being sprayed in the hope of destroying those yellow spring flowers, even though they are less likely to damage the oxalis than the wildlife around and maybe children and pets.

The herbicides in use this time are Triclopyr (the active ingredient of Garlon, in a new formulation called Vastlan) and Aminopyralid (Milestone) – the very persistent pesticide. Also Polaris, or imazapyr.  This is why we support the ballot initiative to limit toxic herbicide use in San Francisco’s parks. Read about that here:


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The Environmental Danger of Preferring Native Plants

This article is republished with permission and minor edits from Conservation Sense and Nonsense, an environmental blog about current ecological topics including “native plant restorations.” We are publishing it here because we think the opposition to “invasives” by nativist activists – and the focus on “native” plants – is not just a waste of resources but actually dangerous to the environment.


The need for diverse urban forest and the obstacles to achieve that goal

Matt Ritter is a professor of biology at Cal Poly San Luis Obispo and Director of Cal Poly Plant Conservatory. He is the author of several books about California’s unique flora, including A Californian’s Guide to the Trees Among Us. He is considered an expert on the horticulture, ecology and taxonomy of the Eucalyptus genus.

Click on picture to view Professor Ritter’s presentation

In October 2021, Professor Ritter gave a presentation to the California Urban Forests Council, entitled “Underutilized Species for the Future of Urban Wood and Urban Forestry.” He began by explaining why it is important to identify new tree species for our urban forest.

  • “Baja is moving to Oregon,” said Ritter to set the stage. Within 50-80 years trees living in California now will no longer be adapted to the anticipated warmer, drier climate. Trees killed by wildfire in California are not returning. Forests are quickly converting to grassland and shrub. As of 2018, California had lost 180 million trees to drought, disease, bark beetles, heat, and wildfire, which is nearly 5% of the total tree population in California. Adding subsequent years to date, we have probably lost 7% of all of our trees.
  • Trees in urban areas will help Californians cope with warmer conditions because they cool our cities and reduce energy consumption. Fewer trees will mean a lower quality of life, for us and for birds. The loss of our trees reduces carbon storage, which contributes to more climate change.

Ritter then explained why we must diversify tree species in our urban forests.

  • There are over 60,000 tree species in the world and only 7% of tree species are found in urban areas around the world. In California our urban forests are even less diverse. There are only 234 tree species on average in California’s urban forests. The average number of approved tree species for planting in California’s municipalities is only 49 and few species on those approved lists are native to California.
  • Diversity of tree species ensures greater resiliency that enables our urban forests to survive changing conditions.
  • Only 9% of tree species in California’s urban forests are native.
The native ranges of tree species in California’s urban forest.

An inventory of Oakland’s urban forest (street trees, medians, and landscaped parks only) was recently completed. With 535 tree species, the diversity of Oakland’s urban forest is greater than average for California. With 14% native trees, Oakland’s urban forest is more native than average. There are 59 species on Oakland’s list of approved trees, of which only 4 are native to Oakland. The most significant finding of Oakland’s tree inventory is that our urban forest is only 64% “stocked,” meaning that of existing tree wells, only 64% are currently planted with trees. When trees die in Oakland, they aren’t being replaced. I don’t doubt there is a will to plant trees in Oakland. I assume it is a question of means in a city with more pressing needs than resources.

Ritter and his colleagues at Cal Poly have created a website called SelecTree to help Californians choose the right tree for the right site and conditions. There are 1,500 tree species described on SelecTree, using 60 characteristics, such as drought tolerance. SelecTree rates blue gum eucalyptus “medium” for drought tolerance, the same rating as native coast live oak and bay laurel. Ritter clarified that drought tolerance on SelecTree is a measure of how much water the tree species uses. Claims that eucalyptus uses more water than native trees is bogus, like most bad raps about eucalyptus.

Ritter recommended specific tree species, based on their drought and heat tolerance. He said that when diversifying our urban forests “we have to think about Australia” because it is the hottest, driest, flattest, and oldest place on the planet, which is another way of saying that tree species in Australia have survived terrible conditions that are comparable to the challenging conditions in urban environments.

Ritter recommended oak species that are native to Texas; eucalyptus and closely related tree species; and several tree species in the legume family, especially acacia. In each case he mentioned the suitability of tree species based partly on the quality of its wood. Apparently, I’m not the only person in California who is disturbed by huge piles of wood chips wherever trees have been destroyed. Ritter also thinks we should be thinking about how we can use wood when trees are destroyed, rather than building potential bonfires.

Obstacles to diverse urban forests in California

When Professor Ritter took questions from the audience, we learned that the main obstacle to a diverse urban forest in California, adapted to our climate conditions, is the myopic focus of native plant advocates:

Question: “Are we introducing new pathogens to our natives by importing new species?”

Answer: There are many laws and rules that restrict the importation of plants to prevent that from happening. We also import only the seeds of plants, not grown plants. The seeds are sterilized and they don’t carry the pathogens that may exist on grown plants in their native ranges.

Question: “Do we know how quickly birds and insects adapt to new species?”

Answer: “No we don’t, but who cares? We are facing a climate emergency. We have 50 years before life in our cities becomes hell. We have a responsibility to protect the quality of life in our cities. We should stop developing the wild, but cities are different.”

Ritter anticipated a question that is often a concern of native plant advocates by saying we should not be concerned about “weediness,” AKA “invasiveness.” He said, “That should be far down on our list of priorities of what to worry about. We need to be primarily concerned about what tree species will grow in our changed climate.”

Rhetorical Question: “But insects need native plants!

Answer: Ritter instantly recognized the mantra of Doug Tallamy. He replied that it is not well established that there are more insects living on native plants than on introduced plants. He mentioned a single study that inventoried plant and animal species in eucalyptus compared to oak forests, presumably Dov Sax’s study which concluded: “Species richness was nearly identical for understory plants, leaf-litter invertebrates, amphibians and birds; only rodents had significantly fewer species in eucalypt sites. Species diversity patterns…were qualitatively identical to those for species richness, except for leaf-litter invertebrates, which were significantly more diverse in eucalypt sites during the spring.”

Rhetorical Question: “We are still dealing with a legacy of blue gum eucalyptus in the Bay Area. Why should we repeat that mistake?”

Answer: Ritter agreed that blue gum eucalyptus is “inappropriate” in many places where it was planted in the Bay Area, but we’re not planting blue gums. There are 800 eucalyptus species and many are ideal for our conditions. He said, “Why not plant eucalyptus? It would be dumb not to plant suitable eucalyptus species just because it shares a name.”

Ritter added that, “Planting only natives just doesn’t work in San Francisco. There would be no trees in Southern California because we don’t have very many native trees in California.” The pre-settlement coast of California was virtually treeless in most places and that’s a fact. For example, a study of historic vegetation in Oakland, California reported that only 2% of pre-settlement Oakland was forested with trees. “Vegetation before urbanization in Oakland was dominated by grass, shrub, and marshlands that occupied approximately 98% of the area.” (1)

San Francisco in 1806 as depicted by artist with von Langsdoff expedition. Bancroft Library

Oakland as a case in point

The San Francisco Chronicle recently published an article about a guerilla tree-planter in Oakland who is planting native oak trees on public land, wherever he wants. Oakland’s Director of Tree Services, David Moore, gently suggests that many of these tree plantings are ill-advised: “‘There is a part of all of us that loves with our hearts the coast live oak tree because of its heritage, the symbolism of our city, and just the legacy that they have,’ Moore said. ‘But we have to diversify, and we are diversifying to other ones that are recommended to be more adaptable to climate change…The reality is that we have created a world that is not the native conditions of these plants,’ Moore said. ‘If we want trees to survive in these non-native conditions, we have to pick trees from around the world that can survive these conditions.’…Moore said oaks, while beautiful, are not the ideal tree for today’s hot, dry and cramped urban landscape. Without careful and costly maintenance, he said, oaks could destroy sidewalks, block light from streetlamps and grow their branches into streets and walkways, creating hazards for motorists and pedestrians. The city still plants oaks, but mainly in parks rather than streets because that’s where they do better, Moore said…”


So, here we are. We have a pressing need for a more diverse urban forest that is adapted to present and anticipated conditions, but we are paralyzed by the ideological commitment of native plant advocates who are demanding that we destroy our urban forest because it is predominantly non-native. In a recent edition of Nature News, Jake Sigg [considered a doyen of Nativism in San Francisco, who runs a long-lived newsletter] said, “Hysterical tree planting is worse than a waste of time and resources…”

I am grateful to Professor Ritter for being bluntly frank with members of the arborist community who should know better. Dare we hope they learned something from that presentation?

(1) Nowak, David, “Historical vegetation change in Oakland and its implications for urban forest management,” Journal of Arboriculture, 19(5): September 1993

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EPA Acknowledges Herbicides Harm Wildlife

This article is republished with permission from the site, Conservation Sense and Nonsense. It points out that the Environmental Protection Agency has finally acknowledged what environmentalists have recognized (and nativists denied) – that herbicides are harmful to wildlife. They are ecologically problematic.


“Restoration” professionals aggressively defend their use of herbicides because it is their preferred method to eradicate non-native plants.  Herbicides are the primary method of killing non-native plants because it is the cheapest method.  When the California Invasive Plant Council conducted a survey of land managers about the methods they use, they learned that 62% of those surveyed reported using herbicides regularly.  Only 6% of land managers said they don’t use herbicides.

The public usually accepts this poisoning of their parks and open spaces because they believe that wildlife benefits from the eradication of non-native plants.  Although there is little scientific evidence that supports that opinion, it is widely considered the conventional wisdom.  Now we have scientific confirmation that wildlife is harmed by the herbicides used to kill non-native vegetation.  That new evidence is the focus of today’s report on the Conservation Sense and Nonsense blog.

EPA Biological Evaluation of Glyphosate and Atrazine

The U.S. Environmental Protection Agency has published the final version of its biological evaluation of the most commonly used herbicide by the managers of our public lands, glyphosate.  EPA reports that glyphosate is “likely to adversely affect” 93% of legally protected endangered and threatened plants and animals.  EPA also published similar findings for atrazine that is available HERE.

Source: EPA biological evaluation of glyphosate

This evaluation is the result of a long-fought battle with the EPA.  The settlement of a lawsuit brought by Center for Biological Diversity and Pesticide Action Network in 2016 required the EPA to conduct this evaluation.  A draft of the biological evaluation was published about one year ago and the final version one year later confirms the findings reported by the draft version.  Thank you CBD and PAN for your persistence!

Significance of EPA’s biological evaluation

The public tends to believe the law protects all wildlife, but that is not the case. The fact is, legal protection only applies to species designated by US Fish & Wildlife Service as threatened or endangered.  If a project is known to kill wildlife, there is no legal recourse unless the species has been officially designated as endangered or threatened. 

The more herbicide we use, the more likely wildlife is to become endangered and therefore eligible for endangered status.  Monarch butterflies are a case in point.  Their dwindling population is attributed to the widespread use of herbicides on weeds that provide nectar and pollen needed by all pollinators, including monarchs.  Monarchs and bees are also directly harmed by insecticides such as neonicotinoids.

Hence, the EPA’s responsibility to conduct a scientific evaluation of the effect of herbicides on wildlife applied only to legally protected species.  However, it is essential to understand that the finding applies equally to all plants and animals, whether they are legally protected or not because the physiological processes of all species are similar.  For example, all legally protected amphibians are “likely adversely affected” by glyphosate, according to the EPA’s biological evaluation.  We must assume that all amphibians—whether protected or not—are also adversely affected by glyphosate.

California red-legged frogs are legally protected as an endangered species. Source: USGS
Pacific chorus frogs are not legally protected because they aren’t designated as threatened or endangered. Attribution

What’s to be done about pesticides that harm wildlife?

According to Sustainable Pulse the next official step is:  “The EPA’s evaluations now go to the U.S. Fish and Wildlife Service and National Marine Fisheries Service in the final step of the consultation process to determine what on-the-ground conservation measures are needed to minimize harm to these species and ensure these pesticides do not push any endangered species towards extinction” 

Defenders of wildlife and the public lands on which they live should not stop there.  These are the logical consequences of the fact that the most widely used herbicides should not be used on our public lands:

  • Where pesticides have been banned, they are often accompanied by exemptions for ecological “restorations.”  For example, when rodenticides were banned in California in 2020, exemptions were made for projects claiming to “restore” habitat.  When UC Berkeley banned the use of glyphosate on lawns and playing fields, they exempted glyphosate use off-campus to “restore” habitat.  When East Bay Regional Parks banned glyphosate for use in developed areas such as parking lots and picnic areas, they exempted glyphosate use to “restore” habitat.  These exemptions should be rescinded because they are harmful to wildlife living on undeveloped public land.  Wildlife does not live on parking lots and playing fields.  Wildlife lives in undeveloped areas vegetated with both native and non-native plants.
  • The State of California recently granted a 3-year exemption from CEQA requirements for environmental impact review for projects claiming to “restore” habitat. Available HERE; see (11) This exemption should be revised so that projects that use pesticides are not eligible for exemption from CEQA requirements. 
  • Native plant advocates and “restoration” professionals must quit claiming that projects using herbicides will benefit wildlife, because clearly, they DON’T!
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Season’s Greetings!

This December marks ten years of the San Francisco Forest Alliance. We’d like to reiterate our commitment to protecting our trees and access, and opposing toxic pesticides in the coming years.

The San Francisco Forest Alliance wishes all our readers and supporters Season’s Greetings and a much better 2022!



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Beautiful Trees at Stow Lake to be Cut

San Francisco Recreation and Parks Department (SFRPD) is cutting down more trees. Several supporters alerted us to warning notices on eight large, beautiful trees at Stow Lake that have been marked for destruction. Why? Apparently to repair the perimeter path and bring it into ADA Compliance.

Stow Lake is a good place for birds and wildlife; and these trees are part of their habitat. As one person pointed out:  “People come to the park for these trees — the huge, gnarled, old growth — not for the path: I think the priorities have been convoluted here!  An upgraded disability path can be extended on the lake side of the path to preserve the trees, and the path itself can be raised a little to preserve the roots.”



These are some of the magnificent trees that are to be destroyed.

Here’s what SFRPD has to say:

“Stow Lake Perimeter Path Renovation

Stow Lake is popular destination in Golden Gate Park for strolling, boating and picnicking. The existing asphalt path that circles the perimeter of the lake has deteriorated and is in need of repair. The project’s design will keep the perimeter path in its current alignment to minimize impact on the overall site and the landscaping. Additionally, the site furnishings will be refurbished.

Scope of Work
The intent of this project is to renovate the existing perimeter path at Stow Lake and the site furnishings, including benches and picnic tables to achieve ADA compliance. The construction will be performed in two phases so that half of the perimeter path will be open at all times. No work will be occurring in the area in front of the Boathouse. Eight trees adjacent to the path will be removed based on an arborist’s assessment of the trees’ risk ratings and condition or due to construction impacts. The trees will all be re-planted in a 2:1 ratio.

Funding Source

This project is being funded by multiple sources including the following:
Recovery Stimulus and Critical Repairs
General Fund
Mayor’s Office on Disability

We are currently wrapping up the design phase of the ADA Perimeter Path Project. Later this year, we will be advertising the project to potential bidders. We aim to award the construction contract by Spring/Summer of 2022. The project is anticipated to be complete by early 2023.”


In this era of climate change, every tree counts. While across the world, governments are mobilizing to preserve existing trees – especially large and mature ones – here in San Francisco we seem to want to get rid of them. Every project starts with, first let’s cut down trees. It’s an easy way to spend money and disburse funds, and requires no metric of success.

Is this what the disability community wants?

Could this project have been done without felling eight mature and beautiful trees? Well, obviously. Had the trees been a priority, we are sure the planners would have found a way to keep the trees while rebuilding the path. Architects and landscapers are ingenious at finding solutions. Cutting down trees is a short cut, and a bad one. Planting 2:1 – which as far as we can tell, is not being monitored for compliance – is insufficient. The value of a large tree is huge both in terms of carbon sequestration and habitat, not to mention beauty. It will be decades before any saplings reach that size and ecological contribution.


Write to the Project Manager Alexis Ward, to  SFRPD (and its General Manager Phil Ginsburg), and to the Mayor:

You can also find SFRPD and Phil Ginsburg on Twitter at @RecParkSF and @PhilGinsburgSF
And on Instagram at: @SFRecPark and @PGinsburg

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Toxic Roundup Herbicide, Fruiting Blackberry

The SFRPD’ Natural Resources Department (NRD) is spraying toxic herbicides on Golden Gate Heights park. The pesticides being used are Roundup (glyphosate) and Polaris (imazapyr). Someone recently saw this notice:

Sign indicating pesticide spraying Golden Gate Heights, San Francisco, Sept 2021

On the next visit, the sign indicated that the spraying had been completed on September 2, 2021.

Toxic herbicide notice - imazapyr and glyphosate - Golden Gate Heights San Francisco CA, showing spraying was completed.What’s really bad about this is that one of the target plants is blackberry. Now, while it’s fruiting season.

Blackberry bushes with ripe and unripe fruit


Back in 2017, we caught another such instance, at that time on Mount Davidson. We wrote to the Commission for the Environment in protest, and we published an article here with the details: Pesticides on Blackberry in the Fruiting Season

Here’s what we wrote then: “It’s the time of the year when the blackberry bushes bear fruit, to the delight of children and the public in general (and not a few animals and birds)…. NRD seems willing to go by the letter of the rules, not the spirit of it. Blackberry should not be treated with persistent herbicides at all, especially not in the fruiting season. It’s going to affect children, wildlife, and anyone who loves picking the berries in season… most parkgoers.

At the time, they used only Tier II herbicides. (SF’s Department of the Environment has a three-tier rating system for herbicides: Tier III, Least Hazardous; Tier II, More Hazardous; Tier I, Most Hazardous.) This time, according to the signs, they have used both imazapyr, which is Tier II and Roundup, which is Tier I.


In 2016, the SF Department of the Environment engaged in a lengthy process of trying to improve its restrictions on  some of the most problematic use of pesticides in our parks. (You can read the entire compliance guidelines here as a PDF. It’s from the SF Environment website.  sfe_th_ipm_compliance_checklist – Copy )

Among them, they developed these restrictions:

✓ A written recommendation from a licensed Agricultural Pest Control Advisor (PCA) is required for any pesticide use. Departments that do not have PCAs on staff should contact the SF Environment IPM Manager.

✓ Only pesticides on the current SF Reduced Risk Pesticide List may be used. Usage must fall within the “limitations” listed for each product, along with label requirements.

✓ ‘Most hazardous’ (Tier I) herbicides have special limitations:

  • Use is prohibited for purely cosmetic purposes.
  • Use is prohibited within 15 feet of designated paths. If a park map exists, designated paths are those found on the maps. Otherwise, designated paths are those actively maintained by staff.
  • Use is prohibited within 15 feet of schools, preschools, playgrounds, or other areas frequented by children.
  • Use on blackberry bushes is prohibited when fruit are present 
  • If within the City limits, use requires onsite supervision by a licensed person (PCA, QAL/QAC) o No broadcast spraying with a boom is permitted except for golf courses (targeted spraying only)
  • Certain pesticide use is restricted in designated Red-Legged Frog habitat, which includes Golden Gate Park, Lake Merced, and several other areas in San Mateo and Alameda County.

Clearly, NRD doesn’t care about the preferences of park-goers, who enjoy picking these berries, or it wouldn’t be trying to spray them in the fruiting season.

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We Need to Reduce Toxic Herbicide Use in San Francisco

This note is from Anastasia Glikshtern, an officer of San Francisco Forest Alliance and a long-time San Franciscan.

Why We Need the San Francisco Toxic Herbicides Reduction Act

Most San Francisco residents do not know that the city routinely uses high-toxicity herbicides in parks and on watersheds such as Hetch Hetchy, Crystal Springs, and Alameda.

I was the same. Since 1991 I’d lived less than half a block from the Rockdale entrance to the Mt. Davidson Park and for 9 years had no idea that SF Recreation and Parks Department (SFRPD) regularly uses toxic herbicides in the park.

At the end of the year 2000 I got a dog. The entrance to Mt. Davidson was so close, Glen Canyon on my way to the Alemany Farmers Market on Saturdays. The dog needed walking. We started walking regularly on Mt. Davidson and in Glen Canyon.

I started seeing the signs – “NOTICE Pesticide Application” – regularly.
The chemical names on the notices were not yet familiar to me – except for Roundup.

At a weeding workshop by SLUG at the San Francisco Garden for the Environment in 1992, the instructor was asked for advice on using Roundup on some difficult-to-eliminate plant. Her answer: “Never even think about using this poison”. She distributed a Glyphosate/Roundup fact sheet – quite a damning one.

When I first called IPM (Integrated Pest Management – the phone number is on the notices) to complain about the spraying, I was told that Roundup is very safe and, because of the way it works, it doesn’t go anywhere.

Today it is everywhere, and it has never been safe.

• In March of 2015 the World Health Organization’s International Agency for Research on Cancer classified glyphosate (active ingredient of Roundup) as a “probable carcinogen”.
• In July of 2017 glyphosate was added to California’s Proposition 65 list (chemicals that cause cancer or reproductive effects).
• In August 2018, in DeWayne Lee Johnson v. Monsanto Company, a San Francisco jury awarded $289.2 million in damages to a former Benicia School District groundskeeper with terminal non-Hodgkin’s Lymphoma.
• In March 2019, a jury in a federal court in San Francisco unanimously ordered Monsanto to pay roughly $80 million in damages for failing to warn plaintiff Edwin Hardeman of the cancer risks of Roundup herbicide.
• In May 2019, after less than two days of deliberations, a California jury found Monsanto guilty and ordered it to pay over $2 billion in punitive and compensatory damages to a married couple who both developed non-Hodgkin’s Lymphoma they say was caused by their many years of using Roundup products.
• The 4th trial started in San Bernardino with opening statements on August 5th 2021:
• More than 100,000 people have filed lawsuits against Monsanto/Bayer claiming that Roundup – and the company lying about its safety – caused their lymphomas.

In 2015, the Annual Public Hearing Regarding Pest Management Activities on City Properties was packed. Most of the attendees were speaking against herbicides in parks. You can read about it here : (

The SFRPD herbicide use noticeably decreased in 2016. Then it started going up again in the following years. In 2020 it’s the highest we have records for. It is particularly bad in the SFRPD’s Natural Resource Division (NRD, formerly NAP).

The IPM boasts of huge percentage reductions in some category of herbicides (Tier I toxicity) or in particular herbicide/active ingredient. (SF Department of the Environment uses a three-tier classification for pesticides, where Tier III is Least Hazardous, Tier II is More Hazardous, and Tier I is Most Hazardous.)

However, it is good to keep in mind that the pesticides are moved from one tier to another (Roundup, which is currently Tier I, was Tier II before 2015), or the same active ingredient suddenly becomes “much safer” with a new inactive ingredient (Vastlan – new for SF – has the same active ingredient as Garlon, but is assigned to Tier II instead of Tier I). You can read about it here.

When asked at one of the Commission on the Environment meetings, to commit to reducing herbicide use, the IPM’s answer was: it is impossible, because they might need any and each of the herbicides on the “Reduced Risk” Pesticide List, and the quantity needed is impossible to predict.

When San Francisco Forest Alliance’s representative spoke about the risks of pesticide use at the 2019 Commission on the Environment meeting she was rebuked by a Commissioner, who said the matter should be left to the experts. If all is to be left to “experts” – why bother with public hearings – or, indeed, an Environment Commission?

The attendance at the pesticide hearings and the Commission on the Environment meetings regarding pesticides have decreased to almost zero, even before Covid restrictions. When writing a letter on the subject, I always think “Why bother? Why waste my time?”

I really want the city to stop spraying Roundup (glyphosate) and other toxic herbicide products. Though Roundup has been the focus recently, that’s only because it is so well-known, well-researched, and widely used. Other herbicides may well be as dangerous (and we know for sure that some are).

Other neighbors of Mt. Davidson, Glen Canyon, Bernal Hill, Bay View Hill, McLaren, Marietta Rocky Outcrop, Pine Lake, Twin Peaks, and many other parks, who walk there frequently, also regularly see notices of pesticide applications, or even the actual sprayings. These are neighborhood parks where families go with children and pets.

Unless there’s a law, there’s no way to reduce the use of toxic herbicides in our parks and watersheds. It just will not happen. Going to the voters is the only way to get it.

The ballot proposition, San Francisco Toxic Herbicides Reduction Act, is ready.
The website,, has a legal text of the measure among other things. The law would ban the use of all herbicides, except organic and EPA minimum risk, on city property, excluding only SFO’s airfields, and Harding Park Golf Course which is under PGA contract.

It can be done! The claim that managing land without herbicides is impossible isn’t true:
• France banned all use of synthetic pesticides in public spaces in 2017, and banned garden use starting in 2019.
• There is a petition to follow the French example and ban all pesticides in UK gardens and urban areas.
• In Canada 170 cities and towns are pesticide free.
• Right next to us, in Marin, the Marin Municipal Water District has been herbicide free since 2005 (which was formally incorporated in law in 2015). Most towns in Marin County don’t use herbicides at all, and in the Town of Fairfax, a neighbor notification is required prior to the use of pesticides on private property.
• Right next to us, the City of Richmond had completely banned use of herbicides in weed abatement activities by the city or its contractors in 2016.
• In 2000 the Arcata City Council banned the use of pesticides on all properties owned or managed by the city, by unanimous vote. (The city hadn’t actually used them since 1986.)
• Non-toxic Irvine, started by parents of kids with cancers, convinced the city of Irvine to switch from regular use of herbicides and toxic fertilizers to eliminating all of them under all circumstances and adopting a completely organic pest-management program. The new program also costs less (even with initial investments in soil augmentation included), and water use was reduced by 30%.

Using herbicides is expensive. Pesticides are expensive. They need to be stored in certain way. The applicators need to be certified and supervised. Warning posting is required. Reporting is required.

In 1986 Arcata’s task force cost analysis compared the use of pesticide application to manual vegetation removal and found that increased labor costs were balanced by decreased costs of purchasing, applying, reporting and storing of the pesticides. According to Dan Diemer, Arcata’s Park Superintendent, “From a management perspective it’s actually easier to not use pesticides. The amount of training and paperwork that is required for pesticide use is intense.”

The city of Irvine found that financial benefits come along with ecological and health benefits from eliminating toxic pesticides from landscaping routines.

The parks of San Francisco belong to the people of San Francisco. They have paid to acquire those properties for public use in the past and we are now paying the salaries of those who are managing the parks. The management must not include poisoning of the environment.

[ETA: SFO’s Airfields also excluded from the ballot proposition.]

Posted in "Natural" Areas Program, Applies Pesticides | Tagged , , , | 1 Comment

Nearly 50 Trees on San Francisco’s Market Street Threatened

Here we go again.

San Francisco’s cutting down more trees, as though its paltry tree cover – less than any other major city – needed further depleting. This time, 49 trees on Market Street are planned to be felled to make way for fancy new BART station entrances.

BART entrance with trees – Market St San Francisco. (Copyright Lance Carnes)

These trees are part of San Francisco’s green infrastructure that the city should strive to protect, not heedlessly destroy. And they’re habitat.


Aside from providing nest sites for birds, these trees are the nursery tree of the beautiful butterfly, the Western Tiger Swallowtail. As early as nine years ago, when the Market Street trees were threatened by an ill-conceived street plan, these butterflies were documented as breeding in the London Plane trees (sycamore) that line both sides of market street. (You can read about that here with photos of a just-born butterfly.) These are the famous “Tigers of Market Street” that have been written about in the Smithsonian Magazine, in National Geographic’s Field Notes, in Bay Nature. This little urban ecosystem is a San Francisco treasure – a street that to a bug or bird’s eye, resembles a tree-lined river canyon. Cutting down 50 of these trees is a terrible idea.

(Though the public hearing is over, please do write to SFDPW, your supervisor and to BART about these trees. The relevant Order numbers are: 204929, 204930, 204931, 204932, 204933, 204934, 204935, 204936, 204937, 204938, 204939, 204940, 204941, 204942, 204943)


Trees are a vital part of urban infrastructure.

  • Trees fight pollution, especially particulate pollution that is dangerous to human lungs.
  • Trees improve air quality
  • Trees are good for physical and psychological health; to get the same benefit as living on a tree-lined street, you would have to be ten years younger.
  • Trees provide habitat for wildlife, especially birds and butterflies.
  • Trees help regulate water by absorbing it into their roots and gradually releasing it through their leaves.
  • Trees reduce crime and improve business.

For a detailed list of benefits, read Twenty Reasons Why Urban Trees are Important to Us All

A group that is trying to save these trees estimates their value at $500,000. In fact, given the infrastructure benefits of trees, that is an underestimate. It’s like putting a value on air: It’s free until you don’t have it, and then it’s infinitely valuable.

San Francisco has too few trees.

Unfortunately, every project seems to start with destroying trees – and neighbors never know about it until it’s a done deal and the trees have 30-days-to-death notices on them. Then they object… but the odds are against them. Though they sometimes succeed in saving the trees, more often it’s too late.  Meanwhile, the City seems to be entirely accepting of tree destruction for any and all reasons.

As of 2013, San Francisco had a tree canopy of only 13.7%, the lowest of any major city, and nearly half the appropriate canopy cover of 25%.  Given that this data is now 8 years old, in an administrative environment that favors cutting down trees over saving them, we expect the current situation is worse.

(From SF Data: In preparation for the San Francisco Urban Forest Plan (2013), the Planning Department performed an Urban Tree Canopy (UTC) Analysis using aerial imagery and additional data sets to determine a canopy estimate for the City & County of San Francisco. This analysis estimated San Francisco’s tree canopy at 13.7%  )

Graph showing urban tree canopy cover in major US cities

San Francisco Has the Least Canopy Cover of any Major US City

This is an embarrassment for a “green” city, quite aside from the ecological, environmental and health reasons for saving our trees. Unfortunately, between Nativists, developers, and project managers, there seems to be a wave of tree cutting hitting San Francisco. We’re not augmenting our canopy, we’re shrinking it.

Posted in Fells Trees | Tagged , | 1 Comment

Nesting in the Eucalyptus

Of course it’s no surprise to any of our readers that eucalyptus stands are an excellent resource for nesting birds. A colony of double-crested cormorants nests (or did nest) near Lake Merced; great horned owls nest in eucalyptus trees in Glen Canyon and Golden Gate Park; and flickers nest in an old eucalyptus tree in the Presidio.
But we loved this article by Dr. Allison J. Gong, a life-long Californian, and a marine biologist, backyard beekeeper, columnist for Bay Nature Magazine, and college-level biology professor.

This article was originally published at Notes From a California Naturalist  and is republished here with permission.

(As a comment, we don’t think eucalyptus is dying of “sheer old age” because eucs in California have not reached the typical 200-400 lifespan of these trees, though we don’t know about guano! And we appreciate her question: “At which point, however, does a species cease to be considered non-native?”)


In Morro Bay, CA, there is a stand of eucalyptus trees that has been designated a natural preserve. In 1973 the Heron Rookery Natural Preserve was established to protect great blue herons (Ardea herodias) as they nested. Since then other bird species have taken to nesting in these same trees. When we were there at the end of May we saw these species with nests in the eucalyptus trees:

  • Great blue heron (Ardea herodias)
  • Double-crested cormorant (Phalacrocorax auritus)
  • Great egret (Ardea alba)
  • Snowy egret (Egretta thula)

This particular rookery is not at all removed from human activity. It is right across the street from the municipal golf course and next to a hotel, and there is a walking/biking trail that runs directly under the trees. Signs advise people to keep their voices down, but pedestrians are walking under the trees all day, dodging the rainfall of guano from above. The birds don’t seem to be bothered.

Unlike the Brandt’s cormorants (Phalacrocorax penicillatus), which nest on cliffs and rocks, the double-crested cormorants nest in trees. Birds build nests with local materials, and there is a difference in what I could see making up the nests of these two species. The Brandt’s cormorants at Natural Bridges in Santa Cruz were using seaweeds as the main building material; I could see birds flying back with algae in their beaks, and then either handing it off to a mate on the nest or tucking it into the existing structure itself. In some cases I could see the pieces of algae well enough to make a tentative ID.

Brandt's cormorants (Phalacrocorax penicillatus) nesting on rock arch at Natural Bridges 2021-05-14 © Allison J. Gong

Brandt’s cormorants (Phalacrocorax penicillatus) nesting on rock arch at Natural Bridges 2021-05-14 © Allison J. Gong

Those are the Brandt’s cormorants. The double-crested cormorants nest in the trees, as we saw at the heron rookery. Here’s a pair that have a brood of three chicks:

Double-crested cormorant (Phalacrocorax auritus) parents and trio of chicks 2021-05-23 © Allison J. Gong

Double-crested cormorant (Phalacrocorax auritus) parents and trio of chicks 2021-05-23 © Allison J. Gong

At Morro Bay, which is an estuary rather than a rocky area, the double-crested cormorants use a lot of eelgrass (Zostera marina) in their nests. Eelgrass is very abundant in the Morro Bay harbor and Estero, whereas the birds would have to fly a bit farther to gather algae. Eelgrass, being a true plant, is less slimy than the algae are, and these cormorants’ nests look much drier than the mounds of algae used by the Brandt’s cormorants up in Santa Cruz.

A short distance up the coast at San Simeon the double-crested cormorants were nesting in a smaller rookery, also in eucalyptus trees. I liked the pattern of how these four nests were situated in three-dimensional space:

Double-crested cormorants (Phalacrocorax auritus) nesting at San Simeon 2021-05-23 @ Allison J. Gong

Double-crested cormorants (Phalacrocorax auritus) nesting at San Simeon 2021-05-23 @ Allison J. Gong

Returning to goings-on at the heron rookery in Morro Bay, the herons and egrets were also raising youngsters in that stand of eucalyptus trees. Remember, this rookery is very easily visited by humans. Here’s a view of the trees, taken from the small parking area:

Heron Rookery Natural Preserve in Morro Bay, California 2021-05-23 © Allison J. Gong

Heron Rookery Natural Preserve in Morro Bay, California 2021-05-23 © Allison J. Gong

It’s difficult to photograph the nests because of all the branches obscuring the view. We were also there near mid-day, with the overhead sun making lighting conditions less than favorable for good photography. I did find one comparatively visible heron nest, containing one parent and one sullen punk-ass teenager of a chick. The nestling had started growing feathers but was still almost half fluff, clearly not ready to fly yet.

Great blue heron (Ardea herodias) nest at the Heron Rookery Natural Preserve 2021-05-23 © Allison J. Gong

Great blue heron (Ardea herodias) nest at the Heron Rookery Natural Preserve 2021-05-23 © Allison J. Gong

Both great egrets (Ardea alba) and snowy egrets (Egretta thula) nest at the heron rookery. Here’s a great egret nest with two chicks:

Great egret (Ardea alba) nest at the Heron Rookery Natural Preserve 2021-05-23 © Allison J. Gong

Great egret (Ardea alba) nest at the Heron Rookery Natural Preserve 2021-05-23 © Allison J. Gong

From what I could see, the herons and egrets don’t use any marine material at all to build their nests. One factor that determines the suitability of a potential building material is proximity—even if a certain material is fantastic in other ways, birds may not use it (or may use less of it, compared to other materials) if it costs too much energy to fetch and bring back to the nesting site. For the herons at this site, sticks are easy to come by. Another thing to consider is that herons and egrets are not marine birds. Although some populations live and nest in coastal areas, most do not. Thus it is not surprising that their nests are built from materials that are terrestrial rather than marine.

I did not see any snowy egret nests in areas where they could be photographed well. However, there were some adult snowies in their spectacular breeding plumage. There was enough of a breeze to ruffle up those long plumes that used to be harvested to decorate ladies’ hats.

Look at these beautiful birds!

Adult snowy egret (Egretta thula) in breeding plumage 2021-05-23 © Allison J. Gong

Adult snowy egret (Egretta thula) in breeding plumage 2021-05-23 © Allison J. Gong

Adult snowy egret (Egretta thula) in breeding plumage 2021-05-23 © Allison J. Gong

Adult snowy egret (Egretta thula) in breeding plumage 2021-05-23 © Allison J. Gong

For several decades now, the cormorants, herons, and egrets have been nesting in these eucalyptus trees, which brings to mind the consideration of native versus non-native species. The trees themselves, blue gum eucalyptus (Eucalyptus globulus) are non-native, having been imported to California from Australia starting in the 1870s. This introduction was encouraged by calls to replace native trees that had been cleared for fuel and building material, both of which were desperately needed during and after the Gold Rush. Since ecologists began considering the effects of non-native species in the 1980s there has been a backlash against the blue gums. Given their large size, their having been planted in groups to serve as windbreaks, and their propensity for dropping a lot of debris, they are very conspicuous, and it is easy to get all hot and bothered at how in certain places they dominate the landscape.

Great egret (Ardea alba) in flight 2021-05-23 © Allison J. Gong

Great egret (Ardea alba) in flight 2021-05-23 © Allison J. Gong

At which point, however, does a species cease to be considered non-native? Having been established in California for 150 years, what is the role of E. globulus in the ecology of the Golden State? There are many people and organizations that would like to see the blue gums eradicated, or at least their populations greatly reduced. On the other side of the argument, groups such the San Francisco Forest Alliance posit that blue gums should be treasured as heritage trees.

At the Heron Rookery, some of the eucalyptus trees are dying. One reason is sheer old age. Another is the several decades’ accumulation of bird wastes onto the soil, which is slowly killing the trees. As the blue gums die, the birds will have to find other places to nest. One of the pro-eucalyptus arguments is that many species of native birds—not just these here but other species such as red-tailed hawks, red-shouldered hawks, and a whole host of songbirds—nest in eucalyptus trees throughout the state. If the blue gums are removed, then where will these undoubtedly native birds nest? Especially if the native trees have long been gone?

Taking the long view, my guess is that the birds will figure it out. Ecological communities evolve over thousands of years. The 150 years of the eucalyptus trees’ presence in California seems like a long time, but in terms of ecological time they are merely a blink of the eye. The herons, egrets, and cormorants have been nesting at the Heron Rookery for an even shorter period of time. When this stand of blue gums is gone, due to either natural attrition or removal by humans, the birds will find another place to nest. They might not choose a place that is so easily visited and observed by people, though.

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