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Subterranean Cape sedge (Trianoptiles solitaria)

It is known from one naturalised site in a North Balwyn reserve, Victoria, and is on the National Alert List for Environmental Weeds. It could compete with small native species in suitable southern Australian regions.

Key facts

Type: Weed, herb.

Native to: Cape Province of South Africa.

Established in: VIC.

Other names: Ecklonea solitaria C.B.Clarke.

Best time to act: Nuts germinate in winter, plants flower in spring, and they fruit before dying back in summer.

Identification

  • A small annual, leafy, tufted herb growing to about 200 mm high.
  • Its smooth, slightly fleshy leaves are grass-like and pale green.
  • It has clusters of aerial spikelets and larger basal spikelets hidden at the base of stems and leaves.
  • The aerial nuts are about 2 mm long and have three feathery scales, each mostly divided into three lobes in the upper half.
  • Nuts in the basal spikelets are larger and lack scales.
  • Look-alike: It can be hard to distinguish vegetatively from other small annual sedges, grasses and rushes.
  • Look-alike: Some small Schoenus species have feathery scales or bristles around their nuts, but usually have a zig-zag spikelet axis and six scales or bristles that are not divided apically into three parts.

Where it grows

In Australia, it is known only from a winter seepage area on a grassy slope in a municipal reserve near Koonung Creek in North Balwyn, Melbourne, among a disturbed mixture of native and introduced species.

Why it matters

  • Small, quick-growing annual plants can crowd out native species during their early growth.
  • Although each plant produces only a few seeds, a large population can produce large quantities of seed.
  • The species can naturalise in Australia, and it was placed on the Alert List for Environmental Weeds.

How it spreads

  • Nuts may be moved with soil and mud, including on mowers and other vehicles.
  • Plants produce several nuts per tuft, and the nuts are likely to persist in the soil seedbank for a considerable period.
  • No seed-longevity studies have been done on this species.

Control options

  • Preventing new populations is the most effective control approach.
  • Avoid creating bare areas where it can invade, and detect infestations early so small populations can be more easily eradicated.
  • Monitor sites after control and take measures to prevent the plant spreading to other areas.
  • Report findings to local state or territory weed authorities; consult APVMA information for registered herbicides.

Hygiene and washdown

  • Avoid moving seed in mud on mowers or other vehicles travelling within or between sites.
  • Keep soil and mud on machinery and vehicles from being carried to other areas.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): National Environmental Alert List. One of 28 weeds named on the National Environmental Alert List as early-stage invaders with serious potential to harm the environment.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria

Sources