Ludwigia palustris aka Hampshire Purslane

Ludwigia palustris is a wetland perennial in the evening primrose family, Onagraceae. Its common names include marsh purslane and water purslane. Its native range includes North America, the Mediterranean, and southern Africa. It also grows wild as a rare native in southern England. There, only a few pools hold this plant. It occurs across much of the United States. It grows beside ponds and streams, and on wet mud.

The plant forms low mats with shallow, fibrous roots. Its stems reach about 1 foot [0.3 metres] tall. On land, stems can trail for 2 feet [0.6 metres]. In water, they grow toward the surface, with tips emerging above it. The smooth, fleshy stems range from green to bright red. Roots form at stem nodes and help the mats spread. Paired leaves have smooth edges and a glossy, rubbery surface. Their shape ranges from oval to lanceolate, with blunt tips. Bright sun brings red tones to the green leaves.

Small green flowers appear from midsummer into autumn. They form singly in leaf axils on stems above water. Each flower has a short, tube-shaped calyx with four teeth. It also has four short stamens and a short style. Petals are absent or too small to stand out. Brown capsules follow the flowers and hold many tiny seeds. Each capsule has four angles and a flat top.

Grow this plant in full sun, though it tolerates partial shade. It needs wet ground or shallow water a few inches deep. Fertile bog gardens and pond margins suit it well. It grows in clay, loam, and sand. Sources support acid and neutral soils; NC State also lists alkaline soil. Growth is moderate, with maturity reached in two to five years. RHS rates it H5; NC State lists USDA zones 3–7. Propagate it by division or softwood cuttings. It needs no pruning.

Gardeners use it in aquariums, rain gardens, and water gardens. Its mats help hold muddy banks in place. It also takes up pollutants in bioswales and ditches. Its spreading habit can make it weedy. Sources report few pest or disease problems. Aquatic insects feed on it, and muskrats eat its leaves. People can eat the leaves and stems raw or cooked. The sources give no separate assessment of pet safety.