As an environmental weed, Suberranean Cape sedge can displace other vegetation and thus reduce the availability of habitat for native plants and animals, leading to a loss of biodiversity. The decision to place subterranean Cape sedge on the Alert List was basedon its ability to naturalise in Australia and to produce large quantities of long-lived seed.
Subterranean Cape sedge is native to South Africa. The earliest record of subterranean Cape sedge as a naturalised plant in Australia was of a population found in a municipal reserve near Koonung Creek in North Balwyn, Melbourne in 1989.
Subterranean Cape sedge is known to reproduce by seed. There are two types of ‘nuts’ – from aerial spikelets and basal spikelets.
Subterranean Cape sedge is a small, leafy, annual herb which grows to about 200 mm in height.
The leaves are somewhat fleshy, smooth, light green in colour and tufted. Striations, or veins, run lengthways down the leaf.
Subterranean Cape sedge forms two types of flower spikelet and fruit: aerial spikelets with two flowers that contain both male and female reproductive parts, and basal spikelets which develop beneath the leaves and contain only female reproductive parts. The aerial flower spikelets of subterranean Cape sedge are usually shorter than or equal to the length of the leaves. The ‘nut’, or fruit, that develops from the aerial spikelets is about 2 mm long and narrowly obovoid (egg-shaped) to narrowly elliptic (egg-shaped but pointed at both ends), with a densely pitted surface. These aerial fruits are triangular in cross-section and are wrapped in three hairy scales that each have a long central bristle and smaller side bristles at the top. In contrast, the basal nut is broadly obovoid and larger than the aerial nut, and does not have scales.
Subterranean Cape sedge grows in seasonally damp areas.
CRC for Australian Weed Management. Val Stajsic (National Herbarium of Victoria).
It is possible that subterranean Cape sedge can be eradicated before it becomes widely established. Any new outbreaks should be reported immediately to your local council weed officer and the state herbarium. Do not try to control subterranean Cape sedge without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem. Once the initial infestation is controlled, follow-up monitoring and control will be required to ensure that reinfestation does not occur.
Subterranean cape sedge (Trianoptiles solitaria) is not declared in NSW under the Noxious Weeds Act 1993.