Thanks to the contributions of two energetic people who know plants, chavezpark.org is publishing a complete botanical inventory of the park. Jutta Burger PhD is Lead Scientist for the California Invasive Plant Council, and Bob Huttar is a certified arborist and a consulting field biologist specializing in botany generally and rare plants in particular. Together they are photographing and identifying everything that grows in the park, both common and scientific names. They’ve done the scientific heavy lifting. I’m adding some background blog-talk. We’re publishing the results in a series, with a new installment every Friday.
Four of the five Australians in today’s feature are eucalyptus. The eucalyptus or gum tree has a long and controversial history in the Bay Area. Some 250 species are said to grow in California. It’s no surprise, then, that four species of eucalyptus are found in Cesar Chavez Park, namely the Blue Gum Eucalyptus, the Lemon-scented Gum, the Red Iron Bark, and the Spider Gum. In an effort to keep this post from becoming totally gummy, I’m adding the Blackwood Acacia and the beautiful Shamel Ash, a Mexican native, to the mix.
Blue Gum Eucalyptus
The Blue Gum Eucalyptus (Eucalyptus globulus) is the most common member of the eucalyptus family. It’s grown commercially for pulpwood, and is a source of eucalyptus oil, with China the largest commercial producer. Locally, it has some loyal friends but many powerful foes. Wikipedia has this paragraph:
It was introduced to California in the mid-19th century, partly in response to the Southern Pacific Railroad’s need for timber to make railroad ties, and is prominent in many parks in San Francisco and throughout the state. Naturalists, ecologists, and the United States National Park Service consider it an invasive species due to its ability to quickly spread via seeds and displace native plant communities, while local authorities, especially many fire departments across California consider it to be a major fire hazard, although the United States Department of Agriculture does not list it among its “Invasive and Noxious plants” list in California. Due to these factors, programs across the state of California have been established to remove all eucalyptus growth, and restore native biomes in certain park areas, such as on Angel Island in San Francisco Bay, and in the hills of Oakland, California.
The species turned out to be useless for railroad ties because it twisted and warped as it dried, and became so hard that it was impossible to drive spikes through it. By the time this problem was discovered, the railroad had planted tens of thousands of the trees, many of which remain today.
On the controversy around the Blue Gum, Bob Huttar says:
Even though it can get out of control in northern California and should be managed and not planted, in some places, like the Presidio and Tilden Park, it is one of the defining constituents which many who are fond of that place would object to being removed. An approach many have taken is to eradicate troublesome individuals, cease planting new ones and allowing existing ones to age out and die in due course.
The Lemon-scented Gum (Corymbia citriodora), unlike the Blue Gum, is valued for structural timber. It flowers almost any time of year, a quality prized by bee keepers for honey production. Its main utility is for its oil which, as the name implies, smells strongly of lemon; in various formulations it becomes perfume or a mosquito repellent. It’s considered an invasive weed in parts of Australia, but not (yet?) in California.
Red Iron Bark
The Red Iron Bark (Eucalyptus sideroxylon) is known as the Mugga in its native Australia. It is unusual among eucalypts for two qualities. It has a deeply furrowed bark on the trunk, whereas most eucalypts have smooth bark. And it is so dense that it will not float. Like some other eucalypts, its bark exudes copious amounts of kino, a red sap with medicinal properties and used as a dye.
The Spider Gum (Eucalyptus conferruminata) is a bushy tree, native to Australia, which is valued as an ornamental, a windbreak, for erosion control, and for its non-fussiness about soil types. It strongly prefers coastal habitats. It’s not widespread in California. Calflora reports no observations of this tree in the Bay Area.
So much for the gums. Onward:
The Blackwood Acacia (Acacia melanoxylon) is another Australian native, valued by woodworkers for cabinet making, musical instruments, and wooden boats. However, its growing habits can be obnoxious. Its roots buckle paved surfaces, invade sewer pipes, crowd out native plants, and are extremely difficult to remove. The California Invasive Plant Council lists it as an invasive weed. In some parts of its native range it is considered a pest. It’s abundant in the Bay Area.
This gracious Shamel Ash (Fraxinus uhdei), also known as Evergreen Ash, grows near the park entrance at the corner of Marina Boulevard and Spinnaker Way. It’s a native of Mexico. It’s widespread in Southern California, and not rare in the Bay Area. It does not have a listing of its own in Wikipedia. It’s available in the nursery trade, sold as a specimen tree for shade in large areas, with a warning that its roots will buckle pavement.