Knobby Club Rush Ficinia nodosa (Isolepis nodosa)

Knobby club rush makes a dense tussock of fine, dark green, almost wiry stems, each carrying a small brown knob of flowers near the tip, which is the quickest way to tell it from a lomandra or a true rush at a glance. It is a coastal native of dune swales, estuary margins and clifftop sand around southern Australia, Tasmania and New Zealand. It is used hard in coastal revegetation, in carpark swales and bioretention basins, and in contemporary planting schemes wanting something finer than broad strappy foliage.

Sand, salt and exposure

Its natural ground tells you where it belongs. In the wild it grows where sand is sodden after winter rain and dry by midsummer, in the full blast of salt-laden wind, which is why it gets specified on foredunes and along exposed coastal paths where other tussocks scorch off. Sandy and gravelly soils suit it, and reflected heat off paving does not trouble it. It is a sedge rather than a grass, so clumps stay where they were planted and a mass planting keeps its spacing for years. Plant at roughly five to seven per square metre where continuous cover is wanted, and closer on a dune face where the root mass needs to bind sand sooner. The failure mode is age rather than any pest. An old clump opens out through the middle, the outer stems flop away from a hollow centre, and the planting starts to read as a collection of grey rings. Cut the whole planting back to a low even mound before it reaches that stage rather than after, because clumps left too long take a full season to look right again, and some never fully recover.

Club rush or a tussock grass

Common tussock grass is the softer, blue-grey alternative for inland and southern gardens on ground that holds winter moisture, and it gives movement and tall flower heads that club rush does not. Ficinia is stiffer, darker and much steadier on sand and in salt wind, so a beachfront or estuary planting should start here. Against Little Pal mat rush, the club rush is coarser and more upright, built for civil work rather than a garden bed close to the house. Pick it when the site is genuinely exposed. The two are cut back on much the same cycle, so mixing them through one large bed does not complicate the maintenance. More in natives.

The late winter mound cut

One job runs the maintenance. Cut clumps back to a low even mound in late winter every second or third year, using shears or a brushcutter before new growth moves, and rake the trimmings out of the crowns afterwards. Doing this before a clump hollows keeps a planting even for many years. Remove the seed heads at the same time if seedlings turning up in adjoining beds and gravel would be unwelcome, since it seeds freely. Feeding is close to unnecessary, though a light application of a low-phosphorus native fertiliser after cutting back speeds the regrowth on poor sand. A clump that has already collapsed on an exposed dune face is usually better replaced than nursed.

Choosing a size

This plant is supplied in one size, 130mm, at $16.95 per plant. The size shown is the pot it arrives in, which is the rootball, not the height of the plant. Not sure which to choose? Read our guide to Australian native trees.