by Shane Sody (and ChatGPT)

If you’re walking in your south-eastern Adelaide Park Lands and notice some neat, wiry tussocks topped with delicate corkscrewed seeds, you might be able to identify one or more species of spear-grass.

One of the least-known—and most locally significant—members of this clan is Swollen Spear-grass (Austrostipa gibbosa), a native perennial that survives in just a handful of grassland remnant locations.

Where is it?

Swollen Spear-grass is considered “rare” throughout the Adelaide metropolitan area.

Your best chance to find Swollen Spear-grass within your Adelaide Park Lands is within the fenced native grassland at the southern end of Victoria Park / Pakapakanthi (Park 16), along the Victoria Park Grasslands Biodiversity Trail.

This small, protected patch of grassland is a Key Biodiversity Area. It includes habitat for the rare Chequered Copper butterfly.

*Remnant native grassland in Victoria Park /Pakapakanthi (Park 16). Pic: Shane Sody*

Swollen Spear-grass needs rich loams and seasonally damp grassland/woodland sites—habitats that have been mostly cleared in the city and suburbs.

That’s why the remnant grasslands in the southern part of Victoria Park / Pakapakanthi (Park 16) and in the adjacent Carriageway Park / Tuthangga (Park 17) are so important to protect. They are rare remaining habitat, not only for this plant, but also the insects and soil life that depend on it, within walking distance of the CBD.

From October to January, seed heads and stems are easiest to spot and compare. In cooler months the tussocks are less conspicuous, but still present.

What it looks like

Growth form: Tufted perennial tussock (clump-forming).
Leaves: Narrow, often a little rough to the touch (a common trait in spear-grasses).
Flower/seed heads: A fine, airy panicle that carries the hallmark “spear” seed—a hardened floret with a twisted, corkscrewing awn for drilling into soil. In Austrostipa gibbosa, the seed body (lemma) is asymmetrically swollen on one side (the trait that inspires the name “gibbosa”).
Season: Tussocks persist year-round; flowering/seed display is typically spring–summer.

How to tell it from similar species

Various spear-grasses can look confusingly alike from a distance. Here’s how tell Swollen Spear-grass (Austrostipa gibbosa) from its more common neighbours in your Park Lands:

*Pics, from left:* ***@bmac111 iNaturalist***; ***@nomennudum1 iNaturalist***; ***@knicolson iNaturalist***

Look at the grain (floret) if you can safely examine a fallen seed head.
Swollen spear grass has a distinctly one-sided, swollen lemma (the seed body) — a diagnostic feature. Many other local spear-grasses lack this obvious asymmetric “bulge.”
Compare with Rough Spear-grass (Austrostipa scabra complex):
Very common around Adelaide, A. scabra has open, sparse panicles, longer stems (often 40–70 mm) and lemmas without the strongly one-sided swelling. Leaves often feel notably scabrous (rough)—hence the name.
Compare with Feather/Elegant Spear-grass (Austrostipa elegantissima):
Taller, showier plumes; very long, once- or twice-bent stems (commonly 30–50 mm) and a feathery overall look. Again, no obviously asymmetrical swollen lemma. If the grass looks theatrically “feathered,” think elegantissima, not gibbosa.
Don’t confuse spear-grasses with common weeds like barley grass or wild oats.
Weedy cereals have broader, softer leaves and stems attached to plumper, grain-like seeds. In contrast, native Austrostipa seeds are hard and narrow.

Banner pic (at top): @knicolson iNaturalist;

Want to know more about the plants in your Park Lands? Head over to iNaturalist, where you can record, share, and discuss your findings with fellow naturalists.

There is an iNaturalist page which can show you exactly where citizen scientists (like you!) have observed Swollen Spear-grass (Austrostipa gibbosa).

See the other plants featured in this series here: https://www.adelaide-parklands.asn.au/know-your-park-lands-plants