Xanthorrhoea johnsonii   A.T.Lee 1966

zan-thor-ROH-ee-uh jon-SO-nee-eye

(Xanthorrhoeaceae —  the grass tree family)

Common names: Grass Tree, Black Boy

Xanthorrhoea is derived from two Greek words, ξανθος (xanthos), yellow, and 'ρεω (rheo), to flow, referring to the yellow gum that can be extracted from the plant. I have not been able to ascertain for certain the Johnson after whom the species was named, but I think it likely to have been Vera Scarth-Johnson (1912–1999), an artist and botanist who is noted for her fine botanical illustrations and her continual efforts to teach others to treasure the flora and environment of Australia and, in particular, the botanically rich region of Cooktown and the Endeavour River Valley, on Cape York Peninsula. Although it may appear that her lifetime was too recent to have such an ancient species named after her, it seems the species was named by a contemporary of hers, Alma T. Lee (1912–1990), a botanist at the National Herbarium of NSW, who did a great deal of sorting out of the Xanthorrhoea nomenclature.

in captivity These remarkable plants have a lifespan of about 600 years, and are very slow-growing. The trunk takes a decade to form initially, as it is composed of a mass of old leaf bases held together by a natural resin. It is then a further 20 years or more before the mass of thin, linear leaves rises above it. From then on, it grows only 1 or 2 cm in height per year. The plant eventually grows to a height of over 4 m, and often has branches. However, the flowering stalk grows at a rate of 2–3 cm per day, reaching to a height of 3 m or so. Mature plants will flower every 2 or 3 years.

The Grass Tree attracts a wide range of lizards and insects that shelter in the plant’s foliage. The flowering spear of the plant attracts honey-eating birds, bees, ants, and butterflies. It is known that the plant is an important food source for the endangered mahogany glider.

inflorescence flower detail The Grass Tree was a most useful plant for the indigenous inhabitants of the land. Nectar was collected from the flowering spikes. The stalks from old flowers and fruits were used for tinder in fire-making. The tall brown flower stalks made fine spears, and parts of the soft wood were used to make bases for fire-drills. The soft bases of the young leaves were eaten. Tough leaves were used as knives. Resin was collected from the base of each leaf and used as an adhesive. In some areas the roots surrounding the stem base were eaten.

Unfortunately many of these plants have been lost to land clearance, and to the current wish to use native plants in our gardens. As the plants are so slow-growing, gardeners prefer to plant mature specimens. There is a very high casualty rate in transplanting them, but, even so, saving some of them from the bulldozer must be preferable to losing them altogether. This transplanting is now regulated.

A single flower spike can produce over 9000 seeds, but larvae of the moth Meyriccia latro can be significant seed predators. The caterpillars of Cossodes lyonetii live underground near the plant, and feed on the roots. Those of Ptilomacra senex bore into, and live inside, the living stems, and those of Moerarchis australasiella and Moerarchis clathrata in the dead stems.

Grass Trees can be grown from seed, but the gardener will need plenty of patience (and a long life!) to see the results.

Photographs taken on the old Arcadia to Horseshoe Bay walking track 2009, and in Picnic Bay 2014

Page last updated 12th March 2018







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