Limnocharis flava aka Sawah Flower Rush

Limnocharis flava is a water plant in the Alismataceae family. Its common names include sawah lettuce and yellow velvetleaf. Its native range runs from Mexico through tropical America. This includes parts of the Caribbean and South America. It grows in shallow swamps, pools, and muddy ditches. It also grows along water edges and in rice fields. It favors still fresh water in a wet tropical climate.

This evergreen perennial forms clumps from short, thick rhizomes. It can grow as an annual where seasonal pools dry out. Garden sources give heights of about 2–3 feet [0.60–0.91 metres]. One account describes shorter stems, around 0.7–1.3 feet [0.20–0.40 metres]. Its listed garden spread reaches 2 feet [0.61 metres]. The upright stems are hollow, and the leaves are triangular. Yellow flowers have three lobes and appear on raised stalks. The bloom season varies rather than following a stated month range. The fruits are round. Small fruit units float and carry seeds to new sites.

Grow this plant in full sun and shallow fresh water. It does not tolerate shade. It grows best where water is neutral to slightly acid. Missouri Botanical Garden lists it for USDA zones 10–12. It needs little routine care under suitable conditions. Pond edges and water containers are listed garden uses. These uses apply only where it poses no local invasive risk. Do not plant it where authorities list it as invasive or potentially invasive. Seeds must stay damp or they lose their ability to sprout. Division offers another way to raise plants.

Its rapid spread is the main concern, rather than pests. Missouri Botanical Garden reports no major pest or disease problems. Yet it can crowd out native wetland plants. Dense growth can also block irrigation systems. It has become a serious weed in Asian rice fields and wetlands. Infestations also affect streams and canals. Thick clumps can provide breeding sites for mosquitoes that carry disease. Its value as an ornamental does not remove these risks.

People gather and grow sawah lettuce as a vegetable. Markets in parts of Southeast Asia sell it for food. Cooks use leaves, leaf stalks, flower stalks, and young flower clusters. They boil or steam them, or add them to soups. The edible growth supplies calcium, iron, and vitamin A. The cited sources report no known hazards or medicinal uses. That does not establish safety for pets or every use. Plants also serve as green manure in some places.