Species

Alisma lanceolatum

Common Name(s)

water plantain

Authority

Alisma lanceolatum With.

Family

Alismataceae

Brief Description

A marginal aquatic plant, with lance-shaped leaves, with many tiny pink flowers held on a pyramid-shaped inflorescence, much taller than the rest of the plant.

Flora Category

Vascular - Exotic

Plant Code

ALILAN

Structural Class

Monocotyledonous Herbs

Distribution

Scattered in Hawkes Bay, Wellington and Canterbury.

Habitat

Margins of still and slow flowing water bodies and wetlands.

Features

Leafy emergent perennial herb up to c. 1 m high, although non-flowering plants are much shorter. Aerial parts die off over winter to the rootstock. Leaves all basal, broad ovate 7-23 (28) × 2-5 cm, with a tapered base with a long petiole up to or exceeding the leaf blade. Petiole is semi-circular in cross-section (D-shaped). Submerged or floating leaved plants sometimes occur, these have narrower than emergent leaves. Inflorescence a large, much-branched panicle; branches whorled. Flowers usually pale lilac, c. 1 cm across. C. 20 rounded and flattened seeds (achenes) c. 2.5 mm long, in a dense circular head.

Similar Taxa

Alisma plantago-aquatica has broader lance-shaped leaves and lilac rather than pink coloured flowers. Sagittaria platyphylla has larger flowers on a smaller inflorescence and triangular petioles.

Flowering

Summer

Flower Colours

Red / Pink

Fruiting

Summer to autumn

Year Naturalised

1895

Origin

Native to Europe, North Africa and West Asia.

Reason for Introduction

Possibly ornamental pond plant, or a seed or soil contaminant.

Control Techniques

Rarely problematic and normally controlled in New Zealand.

Life Cycle and Dispersal

Spreads by waterfowl and water dispersed seed.

Attribution

Prepared by Paul Champion and Deborah Hofstra (NIWA).

References and further reading

Clapham, A.R.; Tutin, T.G.; Warburg, E.F.  (1962). Flora of the British Isles.  Cambridge University Press, Second Edition.  1269pp.

Croasdale, H., Flint E. A. and Racine, M. M. (1994).  Flora of New Zealand Volume 3: Freshwater algae, chlorophyta, desmids with ecological comments on their habitats, Staurodesmus Staurastrum and the Filamentous desmids. Manaaki Whenua Press: Lincoln, New Zealand.

Johnson PN, Brooke PA (1989).  Wetland plants in New Zealand.   DSIR Field Guide, DSIR Publishing, Wellington. 319pp.

Preston, C.D.; Croft, J.M.  (1997). Aquatic plants in Britain and Ireland.  Harley Books, 365pp. 

This page last updated on 10 Jan 2014