Quick Facts

Quick facts

  • Subterranean Cape Sedge (Trianoptiles solitaria) is a small annual sedge native to South Africa.
  • It is only known from one site in a reserve in a Melbourne suburb.
  • It has both aerial and basal spikelets and nuts with three feathery bristles.
  • This weed is a potential problem in southern Australian regions with a Mediterranean climate, as it can compete with small native species.

What Does It Look Like?

What is it?

Subterranean Cape Sedge (Trianoptiles solitaria) is a small leafy annual tufted herb that grows to about 200 mm high. The leaves are grass-like, slightly fleshy, smooth, pale green. It has two kinds of spikelets and nuts (fruit/seed).

The flower heads consist of a few small clusters of spikelets. These aerial spikelets have two flowers with both male and female parts; basal spikelets are hidden at the base of the stems and leaves, are larger, and have only female parts.

The nut (fruit) that develops in aerial spikelets is about 2 mm long and has three feathery scales around it; each scale is mostly divided in the upper half into three lobes, the central one bristle-like. The nut in basal spikelets is larger and lacks scales (Stajsic & Albrecht 1992; Wilson 1994; CRC 2003)

For further information on and identification of Subterranean Cape Sedge contact the herbarium in your state or territory.

Flower colour

No flower

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

In its native region, it grows in a Mediterranean climate, in seasonally damp habitats. In its only known naturalised site in the Melbourne area, it grows on a steep slope with low herbaceous vegetation, dominated by Kikuyu Grass Cenchrus clandestinus [as Pennisetum clandestinum]; a winter-moist habitat, where it persists despite the dense grass cover (Victorian Resources Online, no date).

Are there similar species?

Subterranean Cape Sedge would be hard to distinguish vegetatively from a wide range of other small annual sedges, grasses and rushes, both native and introduced. Some small Schoenus species have feathery scales or bristles around their nuts, but they differ from Subterranean Cape Sedge in having spikelets with a zig-zag central axis and having usually six scales or bristles that are not divided apically into three parts (Wilson 2007, pers. comm.).

Why Is It A Weed?

What are its impacts?

Subterranean Cape Sedge was placed on the Alert List for Environmental Weeds because of its ability to produce large quantities of long-lived seed (as a whole population: each plant only produces a few seeds) and ability to naturalise in Australia.

Native ecosystems: Small, quick-growing annual species like this have the potential to crowd out native species in their early stages of growth (CRC 2003).

A detailed impact assessment is available at Victorian Resources Online (http://www.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_subterranean_cape_sedge ).

How does it spread?

Subterranean Cape Sedge is an annual that produces several nuts per tuft (and therefore many nuts annually in that large population) and dispersal would be by movement of nuts with soil and mud. Mowers and other vehicles are potential vectors. Nuts are likely to persist in the soil seedbank for a considerable period, as with many other sedges, but no longevity studies have been done on this species (Wilson 2007, pers. comm.).

What is its history in Australia?

Subterranean Cape Sedge was probably introduced accidentally, as nuts, but exactly how is not known. Being such an inconspicuous plant, it would not have been noticed for many years until the number of plants had built up considerably (Wilson 2007, pers. comm.). It was first noticed in 1989 in a reserve in North Balwyn, Victoria (Stajsic & Albrecht 1992; Victorian Resources Online, no date).

How To Manage It?

Best practice management

Non-chemical control: Preventing establishment of new populations of Subterranean Cape Sedge is the most effective method of control. Avoid creating bare areas where Subterranean Cape Sedge and other weeds can invade. Avoid transporting seed in mud on mowers or other vehicles moving around within or between sites.

All measures should be taken to prevent Subterranean Cape Sedge from invading other areas. It is important to be alert for this species, as small infestations can be more easily eradicated if they are detected early, followed by ongoing monitoring.

Consult your local state or territory weed authorities to report findings of and advice on controlling this species.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

The nuts germinate in winter and the plants flower in spring, fruiting and then dying back in summer (CRC 2003).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Subterranean Cape Sedge is only known from one site near Koonung Creek in a municipal reserve in North Balwyn, a suburb of Melbourne, Victoria (Stajsic & Albrecht 1992). It is on a grassy slope that is a seepage area in winter, about 100 m from the creek, associated with a disturbed mixture of native and introduced species.

By 1999, it was estimated that there were more than 100,000 plants in an area about 200 × 50 m, with smaller outlying populations nearby. The infestation persists, but there is no evidence that it has spread into undisturbed areas or moved beyond the site (Victorian Resources Online, no date).

This species could be a problem in regions of southern Australia with a Mediterranean climate (parts of Victoria, South Australia and Western Australia), extending as far north as southern New South Wales (Wilson 2007, pers. comm.).

Where does it originate?

Subterranean Cape Sedge is native to the Cape Province of South Africa (CRC 2003). The other two species in the genus are also found only in that Province. No species of Trianoptiles is native to Australia (Wilson 2007, pers. comm.).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?

Not declared in any Australian state or territory

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Trianoptiles solitaria

Other scientific names (synonyms)?

Ecklonea solitaria C.B.Clarke

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