You're sure to be impressed when you see our six-meter specimen of heath-leaved banksia, Banksia ericifolia L. f. (family Proteaceae), growing next to the aloe collection on the edge of the desert garden. Like giant fat candles, six centimeters wide and fifteen to thirty centimeters tall, dense erect spikes of golden and orange flowers decorate the branches.
Banksia is one of the most celebrated genera from Australia, named by Linnaeus's son to honor Joseph Banks (1743-1820). While a young man, Banks accompanied Captain James Cook on the famous voyage during which they "discovered" Australia and claimed that huge landmass for the British in 1770. The explorers landed on the shores of eastern Australia in Botany Bay, and, according to legend, a banksia was the first specimen that Banks collected there. Later he was knighted and became not only president of the Royal Society of London but also a wealthy patron of the sciences and chief scientific advisor to King George III of England--the same individual who attempted to suppress independence for our own American colonies.
The genus Banksia includes seventy-two species, all but one of which is endemic to Australia (that one occurs in New Guinea). Also called heath banksia and red-honeysuckle, Banksia ericifolia is the most spectacular of the species in eastern Australia. It grows mostly on sandy heathland and sandstone along coastal bluffs, in the dry sclerophyll forests and woodlands of New South Wales and southern Queensland, Australia, and in the Blue Mountains near Sydney. In nutrient-poor soils, B. ericifolia tends to be a stunted shrub, or it may grow as a small tree, like ours (accessioned in 1968), which has a trunk exceeding twenty-five centimeters in diameter and covered with rough-textured gray bark. In the wild, this plant is not at all fire-adapted; it dies during fire and is reestablished via its paper-winged seeds.
The Latin epithet ericifolia means "leaves like Erica" (family Ericaceae), referring to the common heath of Europe, which forms very narrow, linear evergreen leaves that are relatively short and revolute in form (that is, having both leaf margins rolled inward to the lower side). On our specimen of B. ericifolia, the leaf blade is fifteen to twenty millimeters long and one millimeter wide; the upper leaf is green, and the bottom bears a dense layer of whitish hairs everywhere except along the midvein; and the leaf tip is bifid, having two diverging short points. In some ways, this small tree with its ericoid leaves superficially resembles a needle-bearing conifer--until you spot the stunning inflorescence!
The flowers of B. ericifolia comprise a highly specialized and complex structure that can be enjoyed as a whole--like a flamboyant, wiry bottlebrush--but only understood on intimate examination with a good hand lens. Initially, the inflorescence forms as a solid cylinder (about fourteen millimeters thick) with tight pairs of flower buds arranged in twelve to fifteen vertical rows, in such a way that when the flowers open, these vertical series of flowers can be easily discerned. Flowers begin opening at the top of the inflorescence, gradually progressing downward over the course of many weeks. More than a thousand individual flowers may cover a single inflorescence (I counted!).
As it opens, each flower reveals two really showy parts: the four anthers, which form a golden cluster that looks like the head of a snake; and the long, wiry style, which is orange and shaped like an inward-bent coach whip hooked within the perianth, with the stigma temporarily stored beneath the anthers. Before the stigma is freed from its berth to allow pollination, the anthers separate and release their pollen--a state called protandry ("male first")--which helps to avoid self-fertilization. In Australia, the nectar-bearing flowers are pollinated by species of small birds, especially honey eaters. When the styles are fully extended, the inflorescence finally appears to be about six centimeters in diameter.
At MEMBG our heath-leaved banksia flowers throughout the winter and spring months, apparently enjoying a shorter flowering season than it would in its native home. The spent inflorescence remains on the plant for a long time, appearing as a grayish-black "cob" with wiry, withered flower parts and possibly bearing one or more dry, clam-shaped, wooden fruits (called follicles). Woody cobs of some banksias are sold in Australia as home decorations and may be carved to form objects ranging from candleholders to Christmas ornaments.
The banksias, all of which have gorgeous inflorescences, comprise only one genus of a family with 75 genera and nearly 1500 species, of which 60 percent occur only in Australia. One species of Proteaceae that is more commonly cultivated in the Los Angeles region is an Australian silk oak, Grevillea robusta. A magnificent tree when in full flower, G. robusta also has paired flowers arranged in dense inflorescences, but they are colored yellow and red. Additionally, this year you will surely hear much about another Australian protead, the waratah, Telopea speciossima, native to the Blue Mountains of New South Wales. This crimson inflorescence has been chosen as the official flower of the 2000 Summer Olympics that will be held in Sydney, Australia.
ARTHUR C. GIBSON, Garden Director