Facts not Fiction of Eucalyptus Trees

In the heart of San Francisco, blanketing 80 acres of mountainside, is a century-old, vibrant Forest of Eucalyptus trees growing as tall as 200 feet high.

When you’re in the Sutro Forest, it’s hard to believe you’re still in a big city.  You can follow narrow winding trails through the dense Eucalyptus trees filled with birdsong and get lost without a map.  At dusk, you may hear the Great Horned Owls who nest there.  And on a foggy day, it's arguably the most beautiful place, in a beautiful city!

Not only is the Sutro forest strikingly beautiful, it has a 125-year history in the city, and is part of San Francisco’s heritage.  It also has characteristics of an old growth forest.

According to a 2001 report, it is extremely diverse with 93 plant species of note.  But not everyone treasures this amazing place; instead of a life-filled complex ecosystem with huge trees and a dense understory, a vocal minority see 80 acres of non-natives.  As a result they have put a lot of information out there with no sound research to support their claims.

Advocates of the majestic trees and the beloved forest have responded, debunking a number of myths about Eucalyptus trees.

 1.   Nothing grows under Eucalyptus trees because they poison other plants. (FALSE)

A ramble through Sutro Forest will disprove that as effectively as possible.  The undergrowth is dense to impassible in most places, and trails have to be hacked into the forest.

 2.   Eucalyptus trees only live about 100 years. (FALSE)

Eucalyptus trees in the tropical and arid areas of Northern Australia tend to live about 200 years. In temperate, rainy Southern Australia they can live to 400-500 years.

3.   It’s not native. (TRUE)

It comes from Australia, and was brought here around 150 years ago.  Keep in mind, nothing we eat is native either.  Even corn, peaches, avocado, broccoli, strawberry, artichoke, chicken and beef come from somewhere else.  In fact, the only “native” product in most people’s diet is fish.

4.   Eucalyptus trees doesn’t attract / support bees. (FALSE)

Flowers are mainly pollinated by insects, but birds and small mammals may also act as pollinating agents.  In fact, Eucalyptus is particularly valuable as bee pasture, because it blooms year-round.  It also gives honey a distinctive peppermint taste. (The Honey Bee is also not native.)

5.   Eucalyptus pollen causes allergies. (MOSTLY FALSE)

Unlike wind-pollinated plants such as Mountain Cedar, Oak, and a number of grasses, Eucalyptus relies on insects and birds for pollination.  Wind-pollinated plants have light pollen, which is more allergenic.  Insect-pollinated plants have heavy pollen which isn’t broadcast on the wind, and doesn’t cause as much allergy. 

6.   Eucalyptus groves don’t support birds. (FALSE)

Birders have identified over 40 species in Sutro Forest.  Over 100 species of birds use the trees for their seed, nectar, and permanent habitat.

7.   It’s invasive. (FALSE in practice)

With over 700 species of Eucalyptus trees only E. globulus is listed as an invasive species in California, and that is due, in part, from 60 years of overplanting.  In fact, in the San Francisco Bay Area, Eucalyptus forest cover actually declines, not invades, based on sixty years of research by William Russell (USGS) and Joe Mc Bride (UC Berkeley).