Aligator Weed

Alternanthera philoxeroides
Alligator weed is a summer growing perennial plant which grows in water or wet areas. Under warm moist conditions it grows rapidly, covering the surface and destroying aquatic life. It blocks rivers, channels and drains, worsening the effects of flooding.

It is difficult to control and has the potential to invade irrigated agriculture and wetlands across a wide area of Australia.

Where has Alligator weed been found?

  • The presence of Alligator weed in Australia was first noted in Sydney and Newcastle, with smaller infestations on the north and central NSW coast.
  • Then in 1994 it was found in Barren Box swamp near Griffith and other waterways in the irrigation areas of southern NSW.
  • It has also been found in some home gardens in Qld, NSW and Victoria.

Know the enemy - Identifying features of Alligator weed

  • It has glossy green leaves shaped like spears, arranged as opposite pairs along its hollow stem.
  • It produces a white papery flower head, shaped like a ball (8-10 mm), on a short stalk. Flowering normally takes place from November to March.

Mistaken identity

  • Before flowering, Alligator weed can be confused with two common water plants: - Smartweed (Persicaria decipiens) - and Water Primrose (Ludwigia peploides ssp. montevidenis)
  • Alligator weed also has a very similar appearance to another plant in the same family - Alternanthera sessilis. This is a popular leafy vegetable in some Asian communities where it is known as "Mukunu-wenna" or "Ponankani". Botanically the two species are completely different.

A threat to the irrigation industry and wetland habitats
Alligator weed, which has been described as one of the world's worst weeds because of its fast growth and ability to grow in water as well as on land, originated in South America.

  • Alligator normally grows from a small piece of stem. It can grow as a free floating raft, or its roots can attach to the soil.
  • It is one of the greatest threats to rivers, irrigation systems and wetland habitats.
  • It grows rapidly and can choke waterways with disastrous consequences for agriculture and the environment.
  • On land it is more difficult to control because of its extremely dense and extensive system of underground stems and roots.

The community needs to be aware of this weed and the threat that it poses.

 

Efforts to control Alligator weed
Alligator weed is one of 14 weed species declared under Victorian legislation to be state prohibited weeds. These weeds have the potential to become serious threats to agriculture and the environment but can be reasonably expected to be eradicated from Victoria.

This plant is difficult to control and needs to be treated by experienced people.

Do not attempt to remove it by digging, mowing or mulching.

If you suspect that you have Alligator weed on your property, please contact the Department of Natural Resources and Environment - Keith Turnbull Research Institute in Frankston on (03) 9785 0111.

How is it spread?
Alligator weed is spread mainly by the movement of plant fragments. Small pieces float down waterways or can be carried by animals. Accidental spread on machinery, boats, or in soil or hay easily introduces the plant to new areas with disastrous consequences.

How do we prevent further spread?

  • Be aware of Alligator weed - the threat it poses and how it is spread.
  • Identify Alligator weed - know what it looks like. Check channels, swampy areas and inlets to irrigation bays.
  • Notify DNRE of any suspicious plants so that appropriate control measures can be taken if necessary.
  • Clean all machinery and vehicles when moving to/from infested areas.

For more information please feel free to contact us.