Nymphaea mexicana

Mexican water lily

Family: Nymphaeaceae

Origin: Mexico, North America

Mexican water lily growing in a lake.
Mexican water lily is an aquatic weed that roots into the soft sediments at the bottom of lakes and ponds.
Photo credit: Sam Happy

Regional Pest Management Plan (RPMP) status

  • National Pest Plant Accord Species
  • Whole region — Sustained control

View more about the RPMP statuses

General description

Perennial, bottom-rooted aquatic herb. Rhizomes are stout and erect. Stolons are creeping and tuberous. Leaves are floating, round, heart-shaped, < 20 cm in diameter and green with brown flecks on top, with a pink/purple underside. Flowers are yellow, < 15 cm in diameter and borne above the water surface in October – December. Fruit is spherical to ovoid, < 2.5 cm diameter and ripens in summer – autumn.

What you need to know

To help protect our environment:

  • You must not breed, distribute, release or sell Mexican water lily. As Mexican water lily 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 Mexican water lily within the Auckland region, unless you are transferring an existing plant on your land to another location within the boundaries of the same property.
  • You must destroy any Mexican water lily 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 freshwater bodies.

Dispersal

Seeds dispersed by water movement. Vegetative spread from rhizomes and tubers, dispersed by water. Human-mediated dispersal through deliberate plantings.

Impact on environment

Forms dense mats and may displace submerged aquatic plants. Reduces dissolved oxygen levels, affecting fish, zooplankton and other native species.

Control

Site Management

Follow up treated areas 3 times per year.

Recommended approaches

Physical control

Method: Mechanical removal or pull-out.

Plant parts requiring disposal: All parts.

Disposal options: Remove to greenwaste or landfill if practical.

Biocontrol

Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user: Foliar spray emergent foliage with 300ml glyphosate green per 10L of water.

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

Mexican water lily growing on a lake.
It produces large yellow flowers in spring.