Euphorbia serpens aka Matted Sandmat

Euphorbia serpens, or creeping spurge, belongs to the spurge family. It is an annual, which lives for one year. It also goes by matted sandmat and round-leafed spurge. Its native range spans southeastern Canada and much of the Americas. NCSU lists Easter Island as part of its range too. It grows on disturbed ground and in urban sites. It has spread to many regions beyond its native range. Its species name refers to how it creeps.

This low plant grows fast and forms dense mats. It stands about 0.08–0.17 feet [0.025–0.05 metres] tall. It spreads 0.17–1.5 feet [0.05–0.46 metres]. The stems lie flat and root where nodes touch soil. They are square in cross-section and have hairs. Their colour ranges from red to burgundy. Small green leaves grow in pairs across from each other. Each simple leaf has a smooth surface and an unbroken edge. The leaves range from egg-shaped to oblong, with short stalks. Broken stems and leaves give off white, milky sap.

Tiny green and white flowers form cup-like groups called cyathia. Each group holds several male flowers around one female flower. White parts with scalloped edges surround them. Red glands that make nectar sit at their bases. In temperate places, flowers bloom from summer into early fall. Tropical warmth can let them bloom all year. Frost kills the plants in temperate climates. The yellow-green fruit is a capsule with three sections. Each holds one smooth, egg-shaped seed, white to brown. Even young plants bloom, and they make many seeds. Seeds sprout fast, with little or no dormant rest.

Creeping spurge prefers sun but grows in part shade too. It copes with heat and dry soil. It can grow in sand, loam, and clay. Soil must drain well, as wet ground can cause root rot. NCSU lists it for USDA zones 5–11. It suits naturalized sites but becomes a weed in lawns and beds. Fast growth and its many seeds make it hard to control. NCSU reports no serious problems with insects or disease.

People have used this plant in traditional medicine for fever and headaches. They have also used it for skin complaints. These uses do not show that it is safe to eat. Keep plant parts away from children and pets. Its latex holds toxic diterpene esters, which can inflame skin. Eye contact can harm the cornea, sometimes for good. Eating plant parts can blister the lips and mouth.