Water primrose

General description

Emergent, aquatic perennial herb. Stems are creeping or floating, with upright flowering stems. Leaves are < 8 x 3 cm and alternate. Flowers are yellow, < 2 cm in diameter and borne in November – February. Fruit capsule is woody and < 2.7 cm long.

What you need to know

To help protect our environment:

• You must not breed, distribute, release or sell water primrose. As water primrose is a National Pest Plant Accord species, these restrictions apply within the Auckland region and across the whole of New Zealand.
• You must not plant water primrose within the Auckland region.
• You must destroy any water primrose on land that you occupy if it has been planted in breach of the above rules and you are directed to do so by an authorised person.

Habitats

Still and slow-moving water body margins, wetlands, damp ground, pasture.

Dispersal

Seeds dispersed by water movement. Vegetative spread from stem and rhizome fragments, dispersed by water movement. Human-mediated dispersal through contaminated equipment.

Impact on environment

Forms dense mats, displacing other vegetation, clogging waterways, impeding water flow and reducing dissolved oxygen levels. May negatively impact native fauna through habitat alteration.

Control

Site Management

Consider engaging an aquatic pest plant control operator. Contact Auckland Council for control options.

Recommended approaches

Physical control

Method: Dig out.

Plant parts requiring disposal: All parts.

Disposal options: Remove to greenwaste or landfill.

Biocontrol

Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user: Foliar spray of 100 ml glyphosate green per 10 L of water.