Callitriche heterophylla
Family
Plantaginaceae
Flora category
Vascular – Exotic
Structural class
Herbs - Dicotyledons other than Composites
Conservation status
Not applicable
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 narrow. The flowers are small, green and inconspicuous.
Distribution
Waikato River
Habitat
Shallow water lake margins and slow flowing streams.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Detailed description
The stems are threadlike and branched, up to ca 50 cm long. The leaves are opposite and may be submerged or floating. Submerged leaves are narrow 0.5 to 2.5cm long with 2 rounded leaf tip lobes. The floating leaves are oval (ca 1 cm wide), and may form rosettes on the water surface. The leaf bases are joined by a wing-like ridge. The flowers are small, without petals and sepal, but have 2 small white bracts (that act as petals). The flowers occur in the leaf bases. There are 4 tiny fruits per flower that are heart shaped ca. up to 1mm in size, and do not have a narrow winged margin.
Similar taxa
All Callitriche species are superficially similar and have variable vegetative parts . Differs from C. stagnalis by its submerged leaves being narrower than floating leaves. The fruit are less than 1 mm in diameter and winged only at the top.
Flowering
Spring/summer
Flower colours
Green
Life cycle
Reproduces from plant fragments and seed.
Year naturalised
1959
Origin
N. America
Reason for introduction
Probably a soil seed contaminant or contaminant of ornamental pond plants.
Control techniques
Can be controlled manually, mechanically or herbicidally depending on situation.
Tolerances
The taxonomy of the four introduced Northern Hemisphere Callitriche requires further investigation in New Zealand.
Etymology
callitriche: From the Greek kalli ‘beautiful’ and thrix ‘hair’, referring to the beautiful stems
heterophylla: Varied leaves; from the Greek heteros and phullon
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.
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.