Origins

Originally found in Australia and New Zealand, it has been introduced around the world. In the UK it is considered an invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

.

Description

The shoots are rather stiff, carrying narrow parallel-sided leaves in opposite pairs, each leaf being about 4-24mm. Small white flowers with four petals are produced in summer on long stalks arising from the upper leaf axils. The flowers are always above water.

Ecological aspects

The plant grows on the muddy margins of ponds where it forms carpets with 100% cover, or semi-submerged in deeper water, or totally submerged with elongated stems. It does not die back in winter.

Cultivation

C. helmsii is able to grow fully submerged in a cool water aquarium

Aquarium

An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

 or as a submersed or marginal plant in a pond

Pond

A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...

. Once established it can grow vigorously and may need to be trimmed back. Schedule 9 of the UK Wildlife and Countryside Act 1981 lists this plant as one that cannot be caused to grow in the wild.

External links

• BioImages
• Status in N. Ireland includes an introduction on UK information
• Flora of N. Ireland - illustrated
• Close up of flower
• Ecological information