Putting another eucalyptus myth to rest: Lifespan of blue gum eucalyptus

When the native plant movement began in earnest, about 25 years ago, its proponents weren’t expecting blowback from those who value the existing landscape.  As far as they were concerned, the trees had to be destroyed solely because they “don’t belong here.”

When they started destroying our predominantly non-native urban forest, they learned that it wasn’t going to be as easy as they thought.  They began to defend their destructive projects with cover stories to convince the public who didn’t share their devotion to native plants that it is necessary to destroy non-native trees because they are a threat to public safety and to wildlife.

One by one, we have debunked the myths that were used to justify the destruction of our urban forest:


Great horned owl in eucalyptus. Courtesy urbanwildness.org

About 20 years ago, one of the first myths was that eucalyptus trees kill birds. It is an absurd claim that is completely unsupported by reality.  With a lot of careful research, we were eventually successful in convincing the public that birds are not harmed by eucalyptus.  In fact, many bird species are dependent upon the trees for safe nesting and winter nectar.   That myth is dead.

  • The claim that eucalyptus and other non-native trees are more flammable than native trees was a powerful narrative that was more difficult to kill. As wildfires have increased in frequency and intensity in California, that claim is no longer credible because every wildfire occurs in native vegetation.  Again, this myth was eventually disproved by reality.
  • More recently, we have finally put to rest the claim that “nothing grows under eucalyptus.” This myth was based on a theory that eucalyptus emits allelopathic chemicals that prevent the growth of plants in the eucalyptus forest.  Thanks to a recent, rigorous study done at Cal Poly, we know with confidence that the allelopathy story is another myth.

It was not surprising that the nativists, having run out of bogus justifications, created a new narrative.  In parks that the East Bay Regional Parks District had been planning to thin, we began to see clear cuts.  When we inquired about why it was necessary to destroy ALL of the trees, we were told they were hazardous.  Then, in the minutes of a meeting of East Bay Regional Park District Park Advisory Committee , we saw the claim that eucalyptus lives only 50-60 years.  Simultaneously, this claim was made in San Francisco by proponents of destroying all eucalyptus trees there.

We eventually tracked down the source of that lifespan estimate to a website called SelecTree, which originally said that the longevity of blue gums is only 50-150 years.  We knew that isn’t an accurate estimate because of how long blue gums live in Australia and how long they have already lived in California.  We provided that information to the authors of SelecTree and were able to get the estimate corrected to “greater than 150 years.”  That’s not nearly long enough, but it is the longest lifespan estimate available on that website and it corresponds with many other trees, including native Coast Live Oak.

In the process of researching the lifespan of eucalyptus, we learned several interesting stories about blue gums that have lived in California for 150 years and are still going strong.  We would like to share some of this information with our readers today.

Blue gum eucalyptus lives in Australia 200-400 years

Blue gum eucalyptus and all other species of eucalyptus are native to Australia.  They were brought to California shortly after the Gold Rush of 1849.  Since they haven’t been in California 200 years, we don’t know how long they will live here.  But how long they live in Australia is obviously relevant to answer that question because longevity is specific to tree species.  We can expect some variation by climate, but not much, and the climate of Australia is similar to the climate in California with wet, mild winters and hot, dry summers.

We know that blue gums live in Australia about 200-400 years because Australian scientists tell us that:

Growth Habits of the Eucalypts by M.R. Jacobs, (Institute of Foresters of Australia, 1955, 1986): Blue Gum eucalyptus lives in Australia from 200-400 years, depending upon the climate.” In milder climates, such as San Francisco, the Blue Gum lives toward the longer end of this range.

That reference was corroborated by John Helms, Professor Emeritus of Forestry at UC Berkeley and an Australian who said in response to our question about blue gums in California, “Blue gums would commonly live for 200 – 400 years, although I presume that some might live longer.”

We also asked the Australian National Botanic Gardens.  They said, “It’s possible that the average lifespan of a native species growing in the wild in Australia would differ to the average lifespan of the same species introduced in northern California, since introduced plants can often “escape” their natural predators when such introductions occur.”

In other words, since eucalyptus trees have more predators in Australia than they do in California, we should expect them to live longer here.  This is called the “predator release” hypothesis.  Ironically, that hypothesis is used by nativists to support their claim that eucalyptus is invasive in California.  (California Invasive Plant Council rates the “invasiveness” of blue gum as “limited.”)  It’s only logical to apply that hypothesis to the question of how long blue gums will live in California.

Many healthy blue gums in California are 150 years old

However, using actual experience in Australia to predict the future of blue gums in California requires some speculation.  Therefore, we turned to the question of how long they have lived in California for guidance.  We found several interesting local stories about blue gums that were planted in California 150 years ago and remain healthy and vigorous today.

There are many examples of blue gums being planted as street trees in California about 150 years ago.  One of the most well-known examples is the city of Burlingame on the San Francisco peninsula. When the City was founded in the 1870s, John McLaren was hired to plant trees to provide a much needed windbreak because the City was nearly treeless, as was the entire San Francisco peninsula.  McLaren planted over 500 eucalyptus (blue gum and manna) along the main highway through Burlingame, along with a row of English elms.  John McLaren was subsequently hired by the city of San Francisco, where he planted many more eucalypts while serving as superintendent of the parks department for 53 years.

The eucalypts in Burlingame are still thriving, but the elms have been dead for about 60 years.  SelecTree says the longevity of English elms is “greater than 150 years,” the longest category of longevity published by SelecTree and completely open-ended.

El Camino Real bordered by Eucalyptus trees. Burlingame, SF Bay area, California, USA

The people of Burlingame greatly value their eucalypts and designated them as “heritage trees” in 1975 under a local ordinance.  That local legal status did not protect them from several attempts by Caltrans to destroy the trees.  The people of Burlingame came to the defense of the trees and were eventually successful in getting permanent legal status to protect 2.2 miles of the trees.  That section of El Camino Real in Burlingame lined with eucalyptus was listed on the National Register of Historic Places in 2012.

Caltrans is now working cooperatively with the people of Burlingame to address safety concerns while “also keeping an eye to the prized grove of eucalyptus trees along the street.”  A task force was formed in 2018 to discuss these issues.  The City of Burlingame remains committed to the preservation of these trees, which suggests that they have a future there. (1)

The life span of street trees is generally much shorter than trees planted as forests because they are subjected to more wind and polluted air of heavily traveled roads, such as El Camino Real.  Although blue gums have passed the test of those challenging conditions with flying colors, they have not been planted as street trees for decades.  Their out-sized scale makes them unsuitable for that purpose.  If blue gums can survive as street trees on heavily traveled roads, they can surely survive longer in the protection of their neighbors in forests.

Blue gums at Stanford University

The blue gums on the campus of Stanford University are another example of 150 year-old blue gums that are very much alive.  Although blue gums were included in the campus landscape design of Frederick Law Olmsted in the 1880s, many of the blue gums actually predate his design:  “Several hundred mighty giants on the campus date back prior to 1870 when Leland Stanford acquired several farm properties, one of which already had avenues of gum trees.  They are mostly Tasmanian blue gums and red gums with a sprinkling of manna trees.”

Eucalyptus on Stanford campus

That description of the old blue gums was written in 1971.  The trees are still alive and well.  I worked on the Stanford campus for 10 years and walked among those trees at every opportunity.

An even older Olmsted design in Oakland

Mountain View Cemetery in Oakland, California was designed by Frederick Law Olmsted in the 1860s.  Like most of the East Bay, the site was treeless.  Olmsted’s design was an eclectic collection of mostly non-native trees, including blue gums.  The cemetery is on steep, windward facing hills, where the windbreak provided by blue gums is particularly valued.

Eucalyptus in Mountain View Cemetery, planted on an unirrigated windward facing hill. 2017

Update:  This venerable old giant was destroyed in September 2018, along with about 150 other trees of different species, including oaks. I did not protest before or after the trees were destroyed because they were on private land and their removal makes way for more grave sites. However, I will mourn its loss.

Olmsted designed a straight avenue through the cemetery lined with magnolia trees.  Many of the magnolia trees have died and those that remain are in poor condition.  SelecTree claims that the life span of Southern magnolia is “greater than 150 years,” which is contradicted by our local experience.

The current owner of the cemetery destroyed many of the blue gums about 5 years ago, in the middle of the extreme drought.  He replaced many of the blue gums with redwoods.  The redwoods are irrigated and are still surviving.  I did not object to the removal of the blue gums because they are on private property.  I confine my advocacy to healthy trees on public land.

Long live the blue gums!

SelecTree has revised its listing of blue gum longevity based on the information we provided.  The myth that our blue gums are dying of old age will not die as easily.  We will have to repeat this information many times and in many different venues, just as we did for every other myth.  If and when that particular myth dies, we can be sure there will be another waiting in the wings.  Ideologies stubbornly persist, despite contradictory evidence.  And yet, we just as stubbornly persist in defense of our urban forest.

(1) Here is the public record, on which my report about the trees in Burlingame is based:

13 thoughts on “Putting another eucalyptus myth to rest: Lifespan of blue gum eucalyptus”

  1. Perhaps we should call the Blue Gum ‘native’ as the trees grow there for such a long time and they grow under hard circumstances.
    Always love reading your posts it helps me to confirm what i see that Eucalyptus trees are a great help to reforestation in many circumstances.
    Thank you.

  2. Great article. Thank you. Today was the day I was going to try to find out the age of the trees in Los Gatos you asked me about. I am sorry. Looks like I took too long to answer you. This appears to be the story you were researching. I have been working on a tough book-editing assignment. Brain wasn’t capable of a side trip. Sorry. Pam



    1. If you find out how old the trees are on Hillow Road I will publish it as an addendum. It’s a good story because it includes a written evaluation of the health of the trees by a widely respected arborist company. Thanks for your help.

  3. Many thanks again, for this research and these postings. The hysterias surrounding tree removals are distressing: True-Believers venting their personal frustrations upon targets they believe can’t or won’t fight back, mostly — that plus a number of wealthy stakeholders benefitting financially — we and the trees need protections from them both. I am a native Californian with Australian ancestors, both proud eucalyptus-tradition places: the answer to, “Should trees have standing?” is an emphatic “Yes!” Defend our euc’s!

  4. Redwoods are my preference where they will grow. The native oak trees are almost as lovely. How about we agree that electric poles and wires are non-natives that damage and endanger the canopy. Lets bury the wires.

    1. Yes, we can agree about that. There are many other improvements in the safety of power lines that are also worth doing and less costly than burying power lines. The fact that nothing has been done by PG&E to make the lines safer, does not speak well for them. The many pending lawsuits against PG&E by people who lost their homes and/or loved ones, will pass final judgment on PG&E.

  5. ours is huge now planted 30 years ago but lately it is dropping a lot of leaves and brown berries requiring daily clean up, i dont know if this means it is not thriving. the berries are a real nuisance as they are slippery.

    1. Do you live in a hot place? Leaf drop can be a reaction to extreme heat and inadequate water. It won’t kill the tree. If it loses a lot of leaves it releafs with epicormic sprouts, explained in this post about trees in San Francisco during the extreme drought: https://milliontrees.me/2014/07/07/relentless-war-on-eucalyptus/
      I’m not familiar with more seed drop than usual from a eucalyptus, however. Some tree species put out a reproductive burst when on their last legs, such as Monterey pines that produce many pine cones before death. But a big acorn year on oaks is an opposite signal of a good year. After a big rain winter, my oak tree produces a big crop of acorns. So, I can’t speculate about the eucalyptus seeds from my experience.
      Good luck. I hope you don’t give up on it.

  6. my one remaining 60 foot Eucalyptus is dropping leaves in May which is a first.
    Planted 1986. How can I save it ?

    thanks for any ideas you have.

    1. Thanks for your question. If you live in a place that is having a period of drought, such as California, that is the likely explanation for your eucalyptus losing more leaves than usual. Dropping mature leaves and closing pores in the leaves (stomata) to retain moisture are mechanisms used by eucalyptus to survive severe drought conditions. If that’s what is happening with your tree, it will eventually releaf with epicormic sprouts. Here is an article on this blog about this phenomenon: https://milliontrees.me/2015/06/23/drought-adapted-eucalyptus-not-dying-by-the-thousand/

      If you are in a place that is in drought, I’m sure your tree would appreciate a deep watering…long and slow so it can absorb and not run off.

      Good luck. I appreciate your effort to save your tree. It is too young to die!

  7. Let’s begin by questioning why there is only one species in the entire animal kingdom whose activities in spreading plants into new habitats is “unnatural”. Birds do it, sheep do it, even chimpanzees do it, but if man does it, it is wicked and evil!

    That said, the 2 biggest problems with blue gums are rot, and horribly incompetent pruning (which generally leads to rot). We have to be honest and recognize that eucs need a LOT of space. People plant them where they don’t have enough room, then have to call for a California chainsaw massacre to keep them within bounds. There is not one tree trimming service in a hundred that knows how to do it properly. And once a euc has been butchered, it is forever dangerous. It is all those badly butcherex trees that end up giving the whole species a fearful reputation. Then the CNPS has a field day demonizing that horrendously deadly invasive foreign species (now officially naturalized in California).
    End of rant!

    1. Your comments are a bit over-the-top, so perhaps you are being sarcastic. Here are a few responses based on the assumption that you are serious.

      Humans are animals. When we “spread” plants we are doing so for the same reason that animals do. To feed ourselves. We brought tomatoes and corn from the New World to the Old World and mangos and cashews from Asia to South America to feed ourselves. That doesn’t make humans “wicked and evil.” Humans are as much a part of nature as any other animal and everything we do is for the same purpose: to survive.

      Blue gum eucalyptus has not been available in nurseries for decades. It is therefore not being planted. There is no reason to be concerned about where people plant them, because they aren’t being planted.

      Blue gum eucalyptus is as likely to need pruning as any other tree and the likelihood that it will be badly pruned is also just as great. Every poorly pruned tree is as likely to be dangerous. In 2008, a visitor to Stern Grove Park in San Francisco was killed by a redwood branch that had been identified by a certified arborist as dangerous several years earlier. The reason why the branch was dangerous was that the tree had been topped by an unqualified tree trimmer who had been instructed to improve someone’s view. So, we can agree that there is some incompetence and negligence in tree care by humans, but blue gums are not singled out for poor care.

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