Grasstree (Xanthorrhoea)

The old bush names for this plant were unkind — “blackboy,” for the charred trunk and the spear-straight flower spike some early settlers thought resembled a person — and the names have rightly fallen away, but the description behind them was not wrong. A mature grasstree does look burnt, more or less permanently, and that is very nearly the point. What looks like a scorched trunk is in fact a tightly packed jacket of the plant’s own dead leaf-bases, built up leaf by leaf over a lifetime and left in place rather than shed, the way a real tree sheds bark. It is a slow construction project: the grasstree’s woody-looking “trunk” is one of the slowest-growing structures in the Australian bush, so a specimen standing chest-high has been building that skirt for far longer than a casual glance would suggest.

That skirt is not decoration. It is fire-fighting equipment. When a bushfire comes through the Mount Lofty scrub, the dead thatch around a grasstree’s trunk goes up fast and fiercely, a torch of a plant seen from a distance. That is exactly what saves it. The blaze in the skirt burns hot but briefly, and it insulates the single growing point at the very centre of the crown, buried under all that char, from the heat that would otherwise kill it outright (Auld 2020). Walk past a stand of grasstrees a few weeks after a fire and you find them blackened to the ground and, at the crown, already pushing new grass-green leaves — one of the more startling resurrections in a forest full of them.

Then comes the reply. In the spring after a fire, grasstrees across a burnt hillside often throw up their flowering spikes together: a tall, single stem crowded with thousands of small cream flowers, sometimes standing taller than the plant that grew it. Fire does not force this: grasstrees flower in unburnt years, and plenty of them skip a season altogether. What fire does is synchronise the timing, so that the flowering response of a whole population is pulled into the same window (Lamont & Downes 2011). The result lands at exactly the right moment for everyone concerned — a mass nectar bar dropped onto fresh, ash-fertilised ground, at the one time the region’s honeyeaters and lorikeets, which work Xanthorrhoea flowers as reliably as they work eucalypts and banksias, can make the most of it (Ford, Paton & Forde 1979). A blackened hillside a year after a fire, spiked all over with pale flowering stems and loud with nectar-feeding birds, is one of the truest pictures the Mount Lofty Ranges can offer of what “built to burn” means.