The New Zealand Plant Conservation Network

Species

Eichhornia crassipes

Common Name(s)

water hyacinth

Authority

Eichhornia crassipes (Mart.) Solms-Laub.

Family

Pontederiaceae

Brief Description

Perennial free-floating aquatic plant, capable of forming dense floating mats of vegetation in still or slow-flowing waterbodies. Plants are rosettes of glabrous leaves, below which a mass of roots hang in the water column. The inflated, spongy leaf stalks provide floatation. Plants are linked by a network of stems to form a dense mat. Flowers are showy, six-lobed, pale lilac in colour, with a deep blue-bordered yellow spot on the uppermost lobe.

Flora Category

Vascular - Exotic

Structural Class

Monocotyledonous Herbs

Distribution

Mostly northern parts of NZ, subject to a national eradication programme since 1950's with few populations now remaining.

Habitat

Still and slow flowing water bodies in warm areas.

Features

Free floating perennial herb. Plants are stoloniferous with daughter plants often attached. Leaves are bright green, often with a spongy inflated petiole. Roots are long and finely divided, and are bright purple when young before becoming black. Flowers are large (7 cm in diameter) in a spike of up to 10 flowers. They are blue-purple with a central yellow eye surrounded by a dark ring on the uppermost petal. The inflorescence stalk (peduncle) bends underwater when fertilized to release many small, ribbed seeds that sink to the bottom sediments after the capsule disintegrates.

Similar Taxa

None.

Flowering

mid summer to early autumn

Flower Colours

Violet / Purple,Yellow

Fruiting

Late summer/autumn

Year Naturalised

1914

Origin

South America, Amazon basin, western Brazil.

Reason for Introduction

Ornamental pond plant

Control Techniques

Notify Ministry for Primary Industries if found.

Life Cycle and Dispersal

Older stolons between individual plants decay to release young plants; the young plants can flower in 3-4 weeks. This species also reproduces by seed. Germination of seeds occurs when hydrosoils are exposed, in shallow water or on stranded mats of the plant. Late summer germination of water hyacinth has been noted at several New Zealand sites. Seeds and plants can be dispersed by water movement, wind, movement of machinery and equipment, and, planned or accidental planting and release by humans.

This page last updated on 21 Aug 2013