Water hyacinth

Water hyacinth is a free-floating, mat-forming, aquatic herb that grows in still or slow-flowing waterbodies.

Description

• Leaves are bright green and smooth, with inflated leafstalks when young.

• Petioles (stalk that joins the leaf to the stem) are swollen.

• Flowers are 7cm in diameter, in a spike of up to 10 flowers. They are pale purple with a yellow centre.

• Roots are 2.5 metres long, bright purple when young becoming black on maturity.

• Older stolons decay to release young plants, it also reproduces via seed.

• Seeds are dispersed by water and possibly waterfowl and other animals.

• Habitats include still and slow-flowing water bodies, lakes, rivers, ponds, and streams.

What you need to know

Water hyacinth forms dense mats, outcompeting native plants and altering habitat structure. It can clog waterways, impeding drainage and recreational activities.

Management approach

Water hyacinth is declared an unwanted organism by the Ministry for Primary Industries (MPI) because it is capable of causing harm to the natural environment, physical resources or human health in Aotearoa/New Zealand.

These species pose a high risk to our environment, economy, recreation, and cultural values.

Rules

Any species declared a pest cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.

Control

Do not attempt to undertake control of water hyacinth yourself. Report sightings to the MPI on Exotic Pest Hotline at 0800 80 99 66 or the online reporting form.

If you've been in a waterway and plan to move to another within 48 hours, you must clean all your gear that has been wet using the 'Check, Clean, Dry' method.

It's vital that everyone uses the Check, Clean, Dry method on all equipment and vessels to stop freshwater pests.