Subterranean cape sedge (Trianoptiles solitaria)

Subterranean Cape sedge is a small leafy plant that grows in damp areas. It can outcompete native plants.

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How does this weed affect you?

Subterranean cape sedge has not been found in NSW. It is an environmental weed that could outcompete native plants and reduce food and habitat for native animals.

What does it look like?

Subterranean Cape sedge is a small, tufted, annual plant which grows to about 20 cm tall. It germinates in winter, flowers in late winter to spring and then dies in summer after producing small nuts (fruit/seeds).

Leaves are:

light green
up to 8 cm long
fleshy, smooth and hairless
striped lengthways down the leaf.

Flowerheads are:

greenish
small (up to 4 cm long)
present in spring
either:
- on stems (aerial) which are as long as, or shorter than the leaves, they have 2 flowers per spike
- below the leaves, partly underground (basal).

Nuts:

There are two types of nuts. Aerial nuts grow on the stems and basal nuts grow at the base of the plant

Aerial nuts are:

2 mm long and 1 mm in diameter
shiny grey green to blackish
narrowly egg-shaped, sometimes with pointed ends
densely pitted
triangular in cross-section
wrapped in three hairy scales with a long central bristle.

Basal nuts are similar to the nuts produced on stems, though they are:

larger than aerial nuts
rounded
do not have scales.

Where is it found?

Subterranean Cape sedge has not been found in NSW. In Australia, it has only been found in Melbourne. The earliest record of subterranean cape sedge as a naturalised plant was in North Balwyn, Melbourne in 1989.

It is native to South Africa, where it is listed as critically endangered in its natural habitat.

What type of environment does it grow in?

Subterranean Cape sedge grows in seasonally damp areas.

How does it spread?

Subterranean Cape sedge reproduces by seed. The nuts could be spread by moving soil or mud.

References

Richardson, F. J., Richardson, R. G., & Shepherd, R. C. H. (2011). Weeds of the south-east: an identification guide for Australia (No. Ed. 3). CSIRO.

Stajsic, V. (2003). Weed Management Guide: Alert list for environmental weeds: Subterranean Cape sedge (Trianoptiles solitaria). CRC for Australian Weed Management.

VicFlora (2026). Flora of Victoria, Royal Botanic Gardens Victoria. Retrieved 12 June 2026 from: https://vicflora.rbg.vic.gov.au/flora/taxon/77161822-209a-4ead-8ae9-8d08e8339789

Von Witt,C. (2008). Plants of Africa: Trianoptiles. South African National Biodiversity Institute. Retrieved 15 June from: https://pza.sanbi.org/trianoptiles

Control

Contact your local council weed officer if you think you have found this plant in NSW.

Hand removal

Small plants can be dug out. Bag the plants if they have any nuts to prevent them spreading.

Disposal

Contact your local council for advice on how to dispose of subterranean Cape sedge.

Herbicide Control

Spot spraying

Spray actively growing plants.

Wiping

This method is suitable for small infestations especially if the plants are close to native plants. Herbicide is wiped directly onto the leaves.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.

PERMIT 9907 Expires 31/03/2030
Glyphosate 360 g/L (Various products)
Rate: One part glyphosate to 50 parts water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

PERMIT 9907 Expires 31/03/2030
Glyphosate 360 g/L (Various products)
Rate: One part glyphosate to 9 parts water
Comments: Splatter gun
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

PERMIT 9907 Expires 31/03/2030
Glyphosate 360 g/L (Various products)
Rate: One part glyphosate to 20 parts water
Comments: Wipe onto leaves
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

Biosecurity duty

The content provided here is for information purposes only and is taken from the NSW Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

For technical advice and assistance with identification please contact your local council weeds officer.

Reviewed 2026