Water hyacinth

General description

Perennial free-floating, mat-forming, stoloniferous aquatic herb. Roots are dark, feathery and < 2.5 m long. Leaves are bright green, rounded and shiny, with bulbous bladder-like leafstalks when young. Flowers are pale purple with darker purple/blue markings and a yellow spot and are borne in clusters above the leaves in mid-summer – early autumn.

What you need to know

To help protect our environment:

• You must not breed, distribute, release or sell water hyacinth. As water hyacinth is a National Pest Plant Accord species, these restrictions apply within the Auckland region and across the whole of New Zealand.

If you see water hyacinth anywhere, you must report it to the Ministry of Primary Industries on 0800 80 99 66.

Habitats

Still and slow-flowing water bodies, lakes, rivers, ponds, streams.

Dispersal

Seeds dispersed by water and possibly waterfowl and other animals. Vegetative spread from stolons and budding, dispersed by water and wind. Human-mediated dispersal through deliberate plantings and movement of contaminated boats and equipment.

Impact on environment

Forms dense mats, outcompeting native plants and altering habitat structure. Clogs waterways, impeding drainage and recreational activities.

Control

Recommended approaches

Do not attempt to undertake control of this species. The Ministry of Primary Industries will carry out the control of this species.