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  3. Mexican water lily
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Management programme
Progressive containment
Objectives
Contain and progressively reduce the amount of Mexican water lily and the number of locations that have it, to reduce its impacts in the Waikato region.
Impacts
Biodiversity, water quantity/quality, social and cultural wellbeing, amenity/recreation

Mexican water lily, a native of the Southern United States and Mexico, is a perennial bottom-rooted floating aquatic plant that was introduced to New Zealand as an ornamental pond species. It’s recognisable by its large, flat, leathery floating spotted leaves and yellow flowers.

What does it look like?

Flowers

  • Star-shaped floating pale-yellow flowers (to 15cm across) that close at night.
  • Petals are many veined.
  • Flowers from October to December.

Fruit/seeds

  • Green berries, which grow underwater that produce seeds (2mm-3mm long).

Leaves/stems

  • Large, flat, mostly round, leathery, spotted floating leaves (to 20cm across).
  • Mature leaves have brown blotches on upper surface, mainly pink-purple beneath.
  • Main vein of the leaf protrudes on the underside of the leaf.
  • Fleshy stems (stolons) bear banana-shaped tubers.

Why is it a pest?

Mexican water lily can occupy the surfaces of lakes and other slow flowing shallow waterbodies, growing rapidly to potentially cover them. It displaces native species by forming dense mats of floating leaves, restricting light penetration to sub-surface species and out-competing surface species. It can clog waterways, restricting water flow and obstructing recreational water users. It may impact on the mauri of wai māori.

Rhizomes, tubers and seeds of Mexican water lily are readily dispersed by water, and fragments can be spread by boats, fishing gear or machinery, or by planting.

Responsibility for control

Waikato Regional Council is responsible for the control of Mexican water lily within the Waikato region. If you think you’ve seen it, call us – don’t try to control it yourself.  

All occupiers are encouraged to report sightings of Mexican water lily on their properties (rule MWL-1 of the Waikato Regional Pest management Plan 2022-2032) and to liaise with the Waikato Regional Council in areas where control programmes are in place.

If Mexican water lily is present on a property that is to be subdivided or developed, there are additional rules and requirements that apply under section 6.6 of the RPMP 2022-2032.

Mexican water lily is banned from being sold, propagated, distributed, or included in commercial displays.

Important

Control methods

If you see Mexican waterlily on your property, don’t undertake any control actions. Call 0800 800 401 to report it to your local biosecurity pest plant officer.

More information

Advice

  • For advice and additional information on mile-a-minute, call our pest plant staff on freephone 0800 800 401.

 

Publications

The following publications are available for download or from Waikato Regional Council. Contact us to request a copy (freephone 0800 800 401).