Pistia stratiotes
Water lettuce
Also known as:
Tropical duckweed
Family: Araceae
Origin: Pantropical
Regional Pest Management Plan (RPMP) status
- National Pest Plant Accord Species
- Notifiable organism
General description
Perennial floating stoloniferous aquatic. Roots are feathery, clustered and < 45 cm long. Stolons are < 60 cm long and hairy. Leaves are light green, hairy, prominently ribbed, formed in lettuce-like rosettes and have wavy margins.
Flowers are minute and borne in clusters within leaf axils. Fruits are small berries containing wrinkled disc-like seeds.
What you need to know
To help protect our environment:
- You must not breed, distribute, release or sell water lettuce. As water lettuce 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 lettuce anywhere, you must report it to the Ministry of Primary Industries on 0800 80 99 66.
Habitats
Still and slow-flowing water bodies, lakes, dams, rivers, ponds, streams.
Dispersal
Seeds dispersed by water and wind. Vegetative spread from stolons and budding. Human-mediated dispersal through dumping of aquarium or ornamental pond waste and movement of contaminated boats and equipment.
Impact on environment
Forms dense mats, outcompeting native plants and reducing water quality. 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.
Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.
