Species

Callitriche stagnalis

Etymology

Callitriche: From the Greek kalli 'beautiful' and thrix 'hair', referring to the beautiful stems
stagnalis: From the Latin stagnum 'pond, standing water, pool', meaning growing in standing water

Common Name(s)

water starwort

Authority

Callitriche stagnalis Scop.

Family

Plantaginaceae

Brief Description

An erect amphibious, slender-stemmed perennial, growing up to 1m tall in shallow freshwater or creeping, prostrate and mat-like on damp ground. Apical rosettes of leaves frequently float on the water surface, submerged leaves broad. The flowers are small, green and inconspicuous.

Flora Category

Vascular - Exotic

NVS Species Code

CALSTA

The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.

Structural Class

Dicotyledonous Herbs other than Composites

Distribution

Widespread and locally abundant throughout NZ.

Habitat

Damp swampy water margins, drains and streams, shallow water margins.

Features

C. stagnalis has slender stems, 10 to 50 cm or more long, with opposite, linear to narrow-lanceolate leaves separated by elongated internodes. Towards the apex, the leaves are typically crowded, obovate or spathulate-oblong and may form floating rosettes. In floating rosettes of apical close-set leaves, the stems are often just/shortly above the water. The upper most leaves are up to 10 mm long by 6 mm wide, while the lower leaves (in pairs) are narrower (but never as narrow as in the native C. petriei). Leaves have 3, 5 or 7 veins. The male and female flowers are separate, on the same plant. The flowers are green and tiny, without petals or sepals, and occur either in pairs or solitary at the base of the leaves. The fruit are ca 1.5 mm in diameter, pale, round and narrowly winged.

Similar Taxa

All Callitriche species are superficially similar and have variable vegetative parts (Lansdown 2008). Species are distinguished by the venation of leaves and shape of their fruit. Leaves obovate and fruit narrowly winged. Submerged leaves wider than those of the native C. petriei.

Flowering

December to February

Flower Colours

Green

Fruiting

Summer to autumn.

Year Naturalised

1912

Origin

Europe and North Africa

Reason for Introduction

Probably a soil seed contaminant or contaminant of ornamental pond plants, possibly native.

Control Techniques

Dense growths of starwort are often a conspicuous feature in drains and can impede waterflow. Can be sprayed or mechanically removed from flowing water channels.

Life Cycle and Dispersal

Reproduces sexually with seeds and spreads vegetatively by creeping stems.

Tolerances

The taxonomy of the four introduced Northern Hemisphere Callitriche requires further investigation in New Zealand.

Attribution

Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).

References and further reading

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

Coffey BT, Clayton JS (1988).  New Zealand water plants:  a guide to plants found in New Zealand freshwaters.  Ruakura Agricultural Cente. 65pp.

Popay et al (2010).  An illustrated guide to common weeds of New Zealand, third edition.  NZ Plant Protection Society Inc, 416pp.

WSDE (2001).  An aquatic plant identififcation manual for Washington's freshwater plants.  Washington State Department of Ecology, 195pp.

Aston, H (1977).  Aquatic plants of Australia. Melbourne University Press, 367pp. Lansdown, R.V. (2008). Water-starworts (Callitriche of Europe) BSBI Handbook 2, London. 180 pp.

This page last updated on 11 Nov 2016