Stratiotes aloides

Water soldier

Family: Hydrocharitaceae

Origin: Eurasia

Regional Pest Management Plan (RPMP) status

  • Unwanted organism

View more about the RPMP statuses

General description

Perennial bottom-rooted aquatic herb that is submerged in winter and floats to the surface in summer. Leaves are deep green, brittle, spiny, sharply pointed and formed in a rosette, resembling a pineapple top. Flowers are white, delicate and borne on stalks in January. Fruits are fleshy berries.

What you need to know

To help protect our environment, you must not breed, distribute, release or sell water soldier. As water soldier is an Unwanted Organism, these restrictions apply within the Auckland region and across the whole of New Zealand.


Still freshwater bodies, lakes, ponds, ditches.


Seeds dispersed by water. Vegetative spread from stolons and plantlets. Human-mediated dispersal through deliberate plantings.

Impact on environment

Can form dense mats, displacing native vegetation. Clogs waterways, impeding drainage and recreational activities.


Site management

Follow up treated areas 3 times per year. Encourage natural regeneration of native plants or replant treated areas where possible after 2-3 treatments to establish dense ground cover and minimise reinvasion.

Recommended approaches

Physical control

Method: Dig out.

Plant parts requiring disposal: All parts.

Disposal options: Remove to greenwaste or landfill.


Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user: Consider engaging an aquatic pest plant control operator. Contact Auckland Council for control options.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Water Soldier plants with a single flower.
An aquatic perennial herb that remains underwater across winter and floats to the surface in summer. Water soldier leaves are deep green, brittle and spiny.
Photo credit: Antonie van den Bos,
Water Soldier partially submerged with a flower.
White flowers with yellow centres form in January. Once pollinated, water soldier flowers form into fleshy berries.
Photo credit: Antonie van den Bos,