Ludwigia palustris - water-purslane, false loostrife, marsh seedbox

Family: Onagraceae - evening primrose
Wetland Indictor Status: OBL

General Species Description

Ludwigia palustris is a prostrate, herbacious perennial with small eliptic leaves and inconspicuous greenish flowers. Both roots and flowers occur at leaf nodes. Stems are round to somewhat square, 10 - 40 cm long at maturity.


Leaves are opposite, 1 - 3.5cm long when mature, and vary in shape. Round to oval to elleptic, the leaf margins are entire. The prominent leaf veins have a pinkish cast; a characteristic which is shared by the roots.


Flowers are only 2 - 3cm long, petalless, with 4 short sepals and stamens. They are greenish-cream-colored, bell-shaped, and emerging at the upper axils. The plant blooms from July to September.


The 2 - 3cm capsules are shaped somewhat like a top, with 4 green stripes. The fruits are many-seeded, and the seeds are smooth.


L. palustris is found in aquatic-bed to emergent wetlands, either floating in standing water or forming mats in muddy soil. The dormant plant can survive long periods of inundation, as in a seasonal lake, and will begin to grow as soon as the water level drops. Veronica (Veronica americana), Watson willow herb (Epilobium ciliatum), and skunk cabbage ( Lysichiton americanum) are known to be its associates.


Ludwigia palustris has an amazing range. As well as being widespread in the pacific northwest and throughout North America, it is also found in South America, Africa, and Greenland.

Similar Species

Veronica (Veronican americana) and Watson willow Herb (Epilobeun ciliatum) may have similarities, but can be easily differentiated from L. palustris. The flowers on each are very distinct from those of Ludwigia - V. americana has terminal clusters of 7 - 10mm wide violet flowers, and those of E. ciliatum are borne on stalks and have reddish to purple petals. The leaves of V. americana and E. ciliatum are serrated, and those of the latter are linear, far longer than they are wide.

Ecological Value

The plant serves as forage for aquatic insects.

Human Value

L. palustris can be a stabilizing plant on muddy banks, and is used to filter and take in toxins in bioswales and ditches.


Cooke, S.S, ed. 1997. A Field Guide to the Common Wetland Plants of Western Washington and Northwestern Oregon. Seattle Audubon Society and Washington Native Plant Society. Seattle Ausubon Society, Seattle, WA, 417pp. Hitchcock, Leo C. and Arthur Cronquist. 1973. Flora of the Pacific Northwest. University of Washington Press, Seattle, WA, and London, England, 730pp.

This page was created by: Jorah Reinstein, August 1999

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