Mexican water lily

What does it look like?

Mexican water lily is a floating leaved aquatic plant with round, heart shaped leaves and large yellow, star shaped flowers. It grows in still or slow flowing water, where it can form dense stands that crowd out other plants. The flowers can grow up to 15 centimetres across and produce small seeds about 2–3 millimetres long.

The plant is rooted in the lake or riverbed and has upright underground stems (rhizomes). Its leaves float on the water surface on long stalks and can grow up to 25 centimetres wide. Mature leaves often have brown blotches on top and are mostly purple underneath. The fleshy stems also produce distinctive banana shaped tubers.

It can be distinguished from true water lilies by its upright rhizomes, the banana shaped tubers, and the deep notch in the leaf that gives it a heart shape. The main leaf vein also sticks out clearly on the underside of the leaf.

Why is it a problem?

This plant grows very quickly and can spread across entire lakes, rivers and ponds. It reproduces through underground stems, tubers and seeds, which are easily carried by water. Small fragments can also spread on boats, fishing gear, machinery or through deliberate planting.

As it spreads, it forms dense mats of floating leaves that clog waterways. These mats block sunlight, smother other aquatic plants, and can make waterways difficult or unsafe for activities like boating, fishing, and swimming.

Control methods

If you see Mexican waterlily on your property, don’t undertake any control actions. Please contact our biosecurity team to report a sighting on 06 835 9200.

More information

This plant is also known as ‘yellow water lily’ and ‘banana water lily’. New Zealand plants are likely to be of hybrid origin but have the characters of the parent species.

Related links

Weedbusters listing: Mexican Water Lily

DOC listing: freshwater weeds

NZPCN listing