(Lagarosiphon major)
Lagarosiphon, photo: Rohan Wells

Status of lagarosiphon in Tasmania

  • Lagarosiphon is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of lagarosiphon are prohibited in Tasmania.
  • The legal responsibilities of landholders and other stakeholders in dealing with lagarosiphon are laid out in the Lagarosiphon Statutory Weed Management Plan.

What does lagarosiphon look like?

  • Lagarosiphon is a perennial (long-lived) freshwater herb with sparsely branched stems to 5 metres long. The plant can be free-floating or anchored on the bottom by rhizomes. The leaves are stiff, finely toothed and curved back towards the stem. The leaves occur alternatively along the stem in a spiral arrangement. Male and female flowers occur on separate plants. The female flowers are tiny, white and three-petalled, and rise to the surface on thread-like stalks. The male flowers detach and float to the water surface.
  • Lagarosiphon overwinters as dormant shoots and rhizomes. These reproductive organs commence growth in spring and produce huge masses of interwoven stems during summer. Flowering begins in summer and continues until early autumn.
  • Only female plants have been recorded in Australia and spread is wholly vegetative. Existing colonies spread from rhizomes on the edge of the colony. Long distance spread occurs when fragments of the plant break off in turbulent water and are carried downstream where they produce new plants. Lagarosiphon has also been spread by the aquarium trade, where it is known as an ‘oxygen plant’.

Impacts of lagarosiphon

  • Lagarosiphon is an aggressive weed that can choke inland waterways and irrigation channels, have a negative impact on water quality, oxygen levels and native aquatic animals, as well as recreational activities such as fishing, boating and swimming.

Where does lagarosiphon occur?

  • Lagarosiphon is a native of southern Africa. In Australia, lagarosiphon has naturalised locally in Victoria.
  • Lagarosiphon has not naturalised in Tasmania.

What you need to do

  • If you locate lagarosiphon anywhere in Tasmania, or if you find a plant that you think could be lagarosiphon, immediately contact Biosecurity Tasmania on 03 6165 3777 to report this weed.

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