Lagarosiphon (Lagarosiphon major) is a State prohibited weed.

Lagarosiphon under water

If you find lagarosiphon

If you think you have seen lagarosiphon, please contact us by:

Please do not attempt to treat or dispose of this weed yourself. We will treat, remove and dispose of lagarosiphon safely, at no cost to the land owner.

Why you must report lagarosiphon

Lagarosiphon is an aggressive freshwater aquatic plant that:

  • chokes still and slow-moving water like lakes and dams
  • depletes oxygen levels in water, resulting in fish kills
  • prevents recreational activities like swimming, boating and fishing

It is easily spread between water bodies by stem and root fragments on boats and trailers.

Once established it is difficult and costly to eradicate.

Lagarosiphon in Victoria

Lagarosiphon originates from southern Africa and has become a major weed in New Zealand and parts of Europe. It prefers the cooler waters of the temperate zone, such as Victoria.

Lagarosiphon has stiff, dark green leaves that spiral around the stem

Plants have been found in New South Wales and Victoria, mainly as an ornamental in aquaria and ponds.

All known infestations in Australia have been eradicated.

Identifying lagarosiphon

Lagarosiphon is an aquatic plant that grows submerged, either rooted to the floor of the water body or free floating.

A mat of lagarosiphon under slow-moving water

Stems can grow up to 5m long. It tolerates a range of water conditions but grows best in sheltered, still or slow-moving water bodies.

Lagarosiphon has stiff, bright green to dark green leaves 5mm to 20mm in length, arranged in alternate spirals along the length of the stem (not in grouped whorls around the stem like its look-alikes).

Only female plants are present outside the native range, which have flowers that:

  • are very small (less than 3mm across)
  • are white to pink or purplish in colour
  • are visible on the water surface from December to April

Lookalike species

Lagarosiphon can be confused with other common aquatic plants such as:

  • Elodea
  • Egeria
  • Hydrilla

Unlike other plants with clusters of leaves that surround the stem, lagarosiphon's leaves spiral and alternate down the stem

Image credits

Illustrated image by Laura Line, University of Florida/IFAS Centre for Aquatic and Invasive PlantsUF/IFAS Center for Aquatic and Invasive Plants.

Page last updated: 02 Apr 2024