Wallum banksia

Start with the plant the whole landscape is named for. The wallum banksia, Banksia aemula, a gnarled, corky-barked shrub-tree, wears its entire life story on its branches at once: fat greenish-yellow flower-brushes at the top, older brushes gone grey and bristling below them, and lower still the spent cones, woody grey knobs studded with what look like half-open eyes and gaping mouths. “Wallum” is widely reported to be the Kabi Kabi word for this banksia, and the country took its name from the tree. That fits. If you had to pick one plant to stand for the whole starved, brilliant sand country, this would be it. It is the champion of living on nothing.

The nothing is real. The banksia grows on the bleached, acid sand of the older dunes, leached over hundreds of thousands of years until barely a trace of nutrient survives. Phosphorus is the one that matters here, and there is almost none of it. One plant answers that poverty three times over, in three directions.

The first answer is chemistry, underground. Where most plants hire fungi to fetch their nutrients, the banksias mostly do their own mining. They grow dense brushes of “cluster roots” that leak acid into the sand and prise the locked-up phosphorus loose themselves. It is self-sufficiency on ground too poor for anything else, and it explains the leaves overhead, hard, tough and long-lived. A plant that pays so dearly for each mouthful of phosphorus cannot afford to build a soft leaf and drop it.

The second answer is those cones, and it is the famous one. Each gaping mouth is a seed-follicle, and on the wallum banksia most of them stay clamped shut for years, holding their seed against the day fire sweeps through. The heat cracks them open and the seed falls onto cleared, ash-fertilised sand, ground swept of competitors and briefly enriched, the moment a seedling has its best chance. The banksia waits for the fire it depends on, and banks a decade of seed for the wait. (These woody knobs are the image behind May Gibbs’s “big bad Banksia men,” though the trees of her own childhood were western species; the wallum banksia’s twisted grey cones are their very likeness.)

The third answer is the loud one. A wallum banksia in flower is a filling-station. The flower-brushes pour out some of the richest nectar in the heath, and the queue runs around the clock: honeyeaters through the day, the eastern spinebill probing with its fine down-curved bill, little wattlebirds squabbling in the branches, the local flagship white-cheeked honeyeater working steadily through the brushes, then the feathertail gliders through the night. Every one of them carries pollen from plant to plant as it feeds. On soil this poor the banksia feeds the heath, and the heath, in return, moves its pollen.

Read those three answers together and you have most of the ecosystem standing up in a single plant. Poverty answered by chemistry in the roots, fire answered by a banked store of seed in the cones, loneliness on the spot answered by a paid courier at the flower: three bargains struck at once, and all three tied to the particular ground the tree stands on. Sweeten the sand and the cluster roots have nothing to do. Shut fire out, or burn too often, and the banked seed never lands in its window. Lose the nectar-feeders and the pollen stays put. Remove any one prop and the banksia, and the country named after it, is in trouble.