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GUEST COLUMNIST: Presidio Park's Eucalyptus Collection

By Parish Rye.

The Eucalyptus genus is a group of flowering trees and shrubs in the myrtle family containing more than 700 species. Almost all of them are native to the continent of Australia. Nine Eucalyptus species are not native to Australia, but are native to the tropical regions of Indonesia, north of the Australian continent.

In recent years, Eucalyptus has been subdivided into three genera—Eucalyptus, Corymbia, and Angophora. The majority continue to remain in the Eucalyptus genus, and they are all commonly referred to as eucalypts.

San Diego first saw the eucalyptus tree in the late 1870s when Eucalyptus globulus (blue gum) was imported as a crop to be harvested for the building of railroad ties and boat hulls. Over the course of a decade or so, thousands upon thousands of blue gums were seen throughout Southern California. It was quickly learned that the way in which E. globulus matured in Southern California soils and climate failed to produce the strong solid wood that it did in Australia. The wood density was far too brittle and weak for manufacturing and thus the original purpose was abandoned. Many of these old stands can still be seen in our region in Ramona, Scripps Ranch, and elsewhere.

Starting in the late 1880s, a horticultural explosion occurred in Southern California when hundreds, if not thousands, of non-native plant species were imported. And the importation of eucalyptus did not cease, either. Between the 1880s and the 1930s, an untold number of Eucalyptus species were brought in as ornamentals.

Three Interesting Eucalyptus Species at Presidio Park

City of San Diego civic leader and philanthropist George Marston developed Presidio Park's landscape architecture with input and advice from, among others, John Nolan and Kate Sessions. His hired park superintendent during the 1930s was Percy Broell, who made eight horticultural maps of Presidio Park in 1937. In these maps, he documents ten Eucalyptus species. The property's plant palette continued to expand over the years and in 1969, botanical specialist Chauncey Jerabek noted twelve Eucalyptus species.

Currently, Presidio Park has twenty-five species of Eucalyptus and a total of 425 eucalyptus trees. Many of the 25 species would be considered common, but several stand out, either because only one specimen exists in the park or because that particular species is rare in Southern California. Three of these particularly interesting species are E. torquata, E. nutans, and E. erythronema.

Eucalyptus torquata

Native to Western Australia, E. torquata is commonly known as coral gum. Torquata means having a twisted collar or ring. E. torquata is an interesting species with a beautiful display of spring or summer pink or red flowers, preceded by the strange twisted and pointed coral colored buds (hence the 'twisted' reference in the species name). This small- to medium-sized eucalyptus, it can reach a height of around fifteen to thirty feet. Considered to be drought tolerant, Presidio Park has several growing on western facing slopes. According to the Australian Native Plants Society, E. torquata is one parent of the well-known cultivar 'Torwood' (the other parent being E. woodwardii).

Eucalyptus nutans

A small shrub-like eucalyptus originating from a restricted area along the south coast of Western Australia, E. nutans has molted bark and shiny foliage. Referred to as the red-flowered moort, this species has crimson flower buds that are nodding with a cream color on the tip, producing a similarly colored flower. This species is a mallee, which refers to the growth habit of certain eucalypts that have multiple stems emanating from an underground lignotuber (woody swelling of the root crown); mallee forests comprise one of Australia's most vital ecosystems. At Presidio Park, visitors are fortunate to be able to see one specimen of this species.

Red-flowered mallee grows on Presidio Park's western slopes. Image courtesy of Casliber.

Eucalyptus erythronema

This beautiful mallee from Western Australia, sometimes called white mallee or red-flowered mallee, has showy red flowers and smooth, distinctive white bark. New bark can be a pale green, or even pinkish in color. It is relatively small compared to other Eucalyptus species, reaching a maximum height of twenty-five feet. Presidio Park has several E. erythronema specimens growing on its most western slopes. Percy Broell noted these in the park in this 1937 maps.

Learn more about the horticulture and history of Presidio Park in Parish Rye's previous article, Presidio Park's Horticultural History.

Parish Rye has been a Park Ranger for the City of San Diego for fourteen years. He conducted a comprehensive plant survey of Presidio Park, documenting all native and non-native plants within the park, which can be viewed on his Presidio Park Horticulture Facebook page.

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