In the Garden:
Northern California Coastal & Inland Valleys
October, 2006
Regional Report

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Luckily, this grass fire was contained before it reached the stand of eucalyptus growing further down the mountain.

Eucalyptus

Did you know there are over 600 species of eucalyptus, many of which thrive in the Bay area? The beautiful red-flowering gum (Eucalyptus ficifolia) that lines Van Ness Avenue is just coming out of bloom now.

The Importation Plan
Eucalyptus were originally introduced to this country from their native Australia during the 19th century for the production of railroad ties. The project was a dismal failure because as the wood dries, it twists, making it most unsuitable for the intended purpose. Thousands of acres of eucalyptus forests were left behind as a reminder of this failed experiment. The trees are very long lived and so well adapted to our deep soil and mild climate that they actually grow better here than in some parts of Australia.

Later, in the early 1900s, these fast-growing trees were commonly planted as windbreaks and for firewood along the newly developing coastal regions. Eucalyptus makes good, but not great, firewood. It needs to season for at least two years to burn properly, and if you don't split it while it's still green, it becomes as hard as stone, quickly dulling even the sharpest axe.

Because of the shedding bark and oily nature of the wood, eucalyptus is prone to burn out of control once ignited. The Oakland Hills fire is a prime example. A hard freeze in December of 1989 left thousands of dead eucalyptus in various states of decline along the ridges and hills in the East Bay. A few years later, a dry offshore breeze in October picked up a spark and soon the entire region was ablaze. Many people blamed the extent of the damage on the eucalyptus.

These trees need pruning on an annual basis when located around "targets" such as homes, parking lots, and sidewalks. Amazingly, these trees can grow up to 15 feet per year in ideal conditions. Because the wood is very dense and brittle, tip pruning is recommended for reducing the weight and making the trees less susceptible to limb drop.

Eucalyptus in California have two major pest problems: long-horned borer, and the lerp psyllid. The lerp psyllid was discovered in southern California in 1998. It's a sucking insect that builds a home on the underside of a eucalyptus leaf. If you watch carefully with a magnifying glass, you can see the tiny insects scurrying in and out of their "front doors." The homes are not all identical, and depending on the severity of the infestation, each leaf may hold several dozen residences. If you find evidence of the lerp psyllid, don't spray. Predatory wasps have been released for control.

Eucalyptus trees are frowned upon by the native plant society. Anybody who has ever tried to garden under one of these shedding giants will understand the concern. Nothing seems to grow under the canopy and layer of leaf litter. Native species can't take hold where eucalyptus are established. That's why there has been a major eradication of species, especially here in northern California. Angel Island State Park in San Francisco Bay is all but void of trees these days.

Whether you consider them friend or foe, eucalyptus are here to stay, being perfectly adapted to our dry summers and alkaline soil. See how many different varieties you can identify within just a few blocks of your own home!


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