Common name: Lagrosiphon
Botanical name: Lagrosiphon major
Management programme: Exclusion, Progressive Containment 

Lagarosiphon is native to Africa and had become weedy in New Zealand by 1950. No seed is produced, with only female plants being found in New Zealand. Lagarosiphon is one of the more common oxygen weeds, made popular through the aquarium trade.

Why is it a pest?

  • Grows rapidly in waterbodies smothering and replacing native vegetation.
  • It reduces the availability of oxygen to native fish, impacting on life-cycles and food chains.
  • Lagarosiphon is spread by broken-off fragments that are easily moved to new sites on boats, trailers, nets and fishing gear.

Where is it found?

  • Lagarosiphon is widely found in the North Island and some parts of the South Island.
  • Risk areas include clear, still, or slow-moving, low fertility freshwater ponds, lakes, streams, and rivers.
  • Present in lakes Rotorua, Tikitapu, Ōkataina, Rerewhakaaitu, Ōkāreka, Tarawera, Rotoiti and Rotoehu.

What does it look like?

  • Lagarosiphon is a wholly submerged, vigorous freshwater perennial up to 4m tall.
  • Leaves are strongly recurved along a brittle stem, arranged spirally and closely packed.
  • Red or pink flowers are present from January to March but are tiny.

What are the rules?


Exclusion pests are not known to be present or established in the Bay of Plenty region. The Bay of Plenty Regional Council is responsible for managing new incursions into the region. Action may be required from landowners or occupiers to support a control operation.

Progressive Containment

Progressive Containment species are pests which the council aims to prevent from spreading, reduce the distribution, or eradicate within parts of the region over time. Landowners or occupiers are responsible for the control of Progressive Containment species on their property. Council may enforce the control of these pest species.

How do you get rid of it?

We are trying to prevent Lagarosiphon from getting into our waterways which have not been infested. If you are travelling with equipment or machinery between waterways please ensure that you check, clean, and dry.

If you would like advice on how to control Lagarosiphon please contact the Bay of Plenty Regional Council.

Management category map