Water purslane, marsh ludwigia
Vascular – Exotic
Herbs - Dicotyledons other than Composites
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.
A wetland or aquatic, and sometimes submerged perennial species. The slender stems are often reddish when submerged, and may be creeping, floating or prostrate and rooting at the nodes. The flowers are solitary, small, green and stalkless. Leaves are glossy, oval and occur in opposite pairs.
Widespread and common in the North Island and northern and western South Island
Still and slow flowing shallow water bodies, swamps and fens.
Hairless herb, sometimes forming dense patches. Glossy ovate leaves up to 3 cm long. The leaves 4 x 2 cm occur in opposite pairs with submerged leaves often red to bronze in colour, petiole to about 1.5 cm long. The stems are often red in colour, creeping or floating and rooting at the nodes. The small green flowers may be tinged with red, do not have petals, but have four broad sepals, and occur in the axils of leaves. The small (4.5 by 2.5 mm) seed capsules have green ribs and the sepals persist. Seeds 0.5 mm long, in several rows.
Ludwigia repens is very similar with opposite leaves and creeping habit, but can be distinguished by the yellow petalled flowers. Ludwigia peploides subsp. montevidensis and alligator weed (Alternanthera philoxeroides). Alligator weed also has opposite leaves, and L. peploides subsp montevidensis has yellow flowers and alternate leaves.
November to April.
Spreads vegetatively by rooting at nodes and fragments dispersed water flow. Can also set seed.
Native to North America and possibly temperate Eurasia.
Reason for introduction
Ornamental aquarium and pond plant.
palustris: From the Latin palus ‘swamp’, meaning growing in swamps
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.; Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp.
Coffey BT, Clayton JS (1988). New Zealand water plants: a guide to plants found in New Zealand freshwaters. Ruakura Agricultural Cente. 65pp.
DiTomaso JM, EA Healy (2003). Aquatic and riparian weeds of the west. University of California Agriculture and Natural Resources Publication 3421, 462pp.
WSDE (2001). An aquatic plant identification manual for Washington’s freshwater plants. Washington State Department of Ecology, 195pp.