Alligator weed thrives on land or water
Here’s a weed that’s got some bite, and it’s threatening farms, market gardens, urban properties, lakes, rivers and wetlands.
Alligator weed is one of the world’s worst pest plants, growing both on land and in water. It’s native to South America and was accidentally introduced to New Zealand in the 1880s in ballast water from ships.
It’s fast growing and difficult to eradicate. Alligator weed can double its area in two months, out competing grass and crops. It’s also toxic to cattle, causing blindness and other health problems. Alligator weed poses a serious risk to farm production and it can completely dominate waterways and lawns.
It takes just a small stem or root fragment to be a source of new growth.
Human activity can be the biggest potential for spread. Alli- gator weed can be transported by soil and water, and it can hitchhike on machinery, boats and even fishing gear. That means it’s essential to check, clean and dry boats and fishing equipment.
On sites with alligator weed or suspected infestations, good weed hygiene is also essential. For example, grass clippings and soil must remain on site and lawnmowers should be washed before leaving the site.
Key features of alligator weed are leaves growing in opposite pairs or whorls along a stem. Stems are hollow and often reddish in colour, and horizontal stems can float on the surface of water, forming rafts. The flowers are white, clover like and papery, flowering December to March.
If you find alligator weed contact the Waikato Regional Council biosecurity pest plants team on 0800 BIOSEC (0800 246 732).
Waikato Weed Watch, by Waikato Regional Council.