Hitchhiking weed takes over wetlands

In the first of our new Waikato weed watch columns, we look at alligator weed, a very serious threat to Waikato rivers, wetlands and other waterways as well as agricultural land.

At present alligator weed is limited to a few sites in the Waikato, including the lower Waikato River, northern shallow lakes and isolated agricultural and urban sites.

It’s an aggressive, rapidly spreading weed that can occupy a wide range of habitats.

In aquatic environments it can be broken up and spread throughout the entire water system.

Alligator weed forms buoyant mats and can completely overtake waterways, resulting in reduced water quality and biodiversity.

The effect on fragile natural environments such as wetlands is devastating.

The weed can also grow vigorously on land where it competes with pasture or crops. It is toxic to stock and very difficult to eradicate.

Even the smallest of fragments can be a source of new growth for some time.

The biggest potential spread is human activity.

Alligator weed happily hitchhikes, accepting rides from fishermen, boaties and other

‘‘Alligator weed happily hitchhikes, accepting rides from fishermen, boaties and other users of rivers that pick up and carry fragments of weed.’’

for users of rivers that pick up and carry fragments of weed on their boats or nets.

Machinery used for excavation or cultivation of land can also provide a ride from one site to another.

Ways for the public to help stop alligator weed’s spread include:

Always clean boats and equipment before leaving any area you’ve been in.

Practice good hygiene with all soil movement equipment.

If you think you see alligator weed report it to Waikato Regional Council on 0800 BIOSEC (0800 246 732). forming matted clumps. Stem and leaf size vary. They can be very compact in lawns or grazed pasture, or much larger when growing in water.

Leaves are in pairs or whorls along hollow horizontal stems.

Flowers are white, papery and clover-like, held erect on stalks.

Waikato weed watch is supplied by staff of the Waikato Regional Council.