Alligator Weed

Alligator Weed plant

(Alternanthera philoxeroides)

Alligator weed - not a vegetable

Alligator weed (Alternanthera philoxeroides) is an aggressive noxious plant that invades Australia’s waterways, wetlands and floodplains. A native to South America, alligator weed is a very difficult weed to manage and detect as it can grow in water and on land.

Infestations of alligator weed have been identified and treated in creeks, lakes, ponds and gardens in the Canberra region. This plant has most likely been spread by plant material from gardens being washed down stormwater drains into our waterways.

Alligator weed is a prohibited and notifiable plant under ACT legislation.

Do not mistake it for mukunuwenna

Alligator weed can be easily mistaken for the Asian vegetable, mukunuwenna (Alternanthera sessilis). Alligator weed is not a vegetable and should not be eaten, transported or grown anywhere in Australia.

To tell the difference between alligator weed and mukunuwenna, look at the flowers. Alligator weed flowers are at least 10 mm across and are found on a short stalk. The stems are hollow and for plants growing on land their stems can have a reddish colour and extensive underground root system. The mukunuwenna flower is smaller (less than 5 mm across) and is found in clusters along the stem where the leaf joins the stem.

Health fears

Health experts believe that extended use of alligator weed in food dishes could lead to serious health concerns.

Environmental dangers

Alligator weed:
  • blocks water storage facilities, waterways and wetlands, preventing use by birds and other wildlife;
  • depletes oxygen levels and restricts light penetration in the water, affecting fish and other aquatic life;
  • crowds out native aquatic plants; and 
  • interferes with water based recreational activities.

You can help stop the spread

Check that you do not have alligator weed growing in your garden.

Call Access Canberra on 13 22 81 if you suspect you have alligator weed. An inspector will confirm its identity and control it free of charge to residents.