Grass-tree

The shaggy mophead on a short blackened trunk looks like nothing much and turns out to be the oldest living thing in sight. A grass-tree, Xanthorrhoea, is neither a grass nor a tree. It builds its trunk from thousands of old leaf-bases packed one on another and cemented with its own resin, and it works so slowly — perhaps a centimetre a year — that a waist-high one has stood here the better part of a century, and the tallest may be three or four hundred years old. On a hillside where the gum trees count their lives in decades, the grass-tree keeps time in centuries.

Almost every part of it reads as an answer to fire. The skirt of dead leaves down the stem catches readily, and a passing fire chars the whole plant black yet does no harm, because the resin-packed trunk and the growing point buried deep in the crown sit so well insulated the heat does not reach them. The grass-tree wears fire the way other plants wear rain. In the spring after a burn it throws up a tall spear, sometimes taller than the plant itself, topped with a dense spike of hundreds of small, nectar-rich cream flowers, and a whole hillside will do it at once, as if on a signal. Which is precisely what it is. Smoke is the cue, and the stand flowers in concert because it was all told the same thing at the same time.

This is a subtly different route from the one the banksia beside it takes. The banksia banks its seed in woody cones and holds it clamped against the day fire cracks them open (that is a story of its own; see serotiny). The grass-tree keeps no such store. Smoke triggers it to flower, throwing its next generation up into the cleared, ash-fed, sunlit window a fire opens. Two mechanisms, one wager: that on this country fire is coming, so hang tomorrow on it. Both go quiet when fire stays away too long. No single right fire, only the rhythm each patch was built around.

Two species dominate the ground you are most likely to walk, though they are not the only ones — X. latifolia, broad-leaved where these are not, is at least as common on the same dry ridges, and X. macronema turns up too. Snap a leaf of the tall ridge grass-tree, Xanthorrhoea johnsonii, and the cut end comes away roughly square, almost as thick as it is wide, the field mark that names it. This is the classic charred column of the open eucalypt forest, holding its ground among the ironbarks and she-oaks on thin, dry, hungry soil, throwing its flower-spike over the grassy floor after a burn.

Follow the ground downhill, into the damp swales and swampy hollows of the sand country, and the grass-tree changes. Here grows Xanthorrhoea fulva, low and all but trunkless, a wet-heath plant that never bothers with a tall stem, its rosette rising straight out of the peaty ground among the wiry sedges. Same slow patience, same answer to fire, two different pieces of country. What parts them is the ground itself: how much water and nourishment it can offer. Dry ridge, and you get the tall square-leaved kind; wet swale, and you get the low trunkless one.

Read it either way and the grass-tree earns its keep. The height of its trunk gives you the age of the slope; which of the two you are looking at gives you your position on the gradient. And once a year, in the season after fire has run through, a whole hillside of these patient, slow-burning clocks throws up its spears at once and comes into flower, on a signal written in smoke.