Matted Sandmat

Euphorbia serpens has naturalized recently in Taiwan.

Herbs, annual, 15-20 cm tall. Root fibrous, 1-2 mm, branched or not. Stems many from base, prostrate, 1-2 mm thick, internodes with adventitious roots, often green, sometimes purple striate, glabrous. Leaves opposite; stipules membranous, triangular, caducous; petiole ca. 1 mm; leaf blade oblong, 2-5 × 1.5-3 mm, gray-green pilose, base truncate or cordate, margin entire. Cyathia single, axillary; involucre turbinate to campanulate, 0.5-0.7 × 0.4-0.5 mm, glabrous, marginal lobes 4; glands 4, reniform-rounded, appendages white, longer and wider than glands. Male flowers 3-5, usually not exserted. Female flower: pedicel ca. 0.5 mm; exserted from involucre; ovary smooth, glabrous; styles free; stigma deeply 2-lobed. Capsule subglobose, 1.5-1.8 × 1.6-1.9 mm, smooth, glabrous; fruiting pedicel ca. 2 mm. Seeds oblong-ovoid, 0.9-1.1 × 0.6-0.9 mm, gray to brown, often smooth, sometimes furrowed; caruncle absent. Fl. and fr. Mar-Aug.

Sandy places along roads and coastal areas. Taiwan (Gaoxiong, Taibei, Tainan, Xinzhu, Zhanghua) [pantropical weed, originally from the New World].

Chamaesyce serpens (Kunth) Small; Euphorbia orbiculata Miquel (1859), not Kunth (1817); E. orbiculata var. jawaharii Rajagopal & Panigrahi.

Small, much-branched prostrate annual herb with hairless branches up to 20 cm long. Leaves opposite, broadly ovate to almost round, up to 4 mm long, cordate at the base; margin entire. Flowers terminal or on short axillary shoots, maroon-purple and white, sexes separate on the same plant. Fruit a 3-lobed capsule, c. 18 mm long, yellowish-green, exserted on a reflexed pedicel.

Native to S America, now a pantropical weed.

Euphorbia serpens is a species of Euphorbia known by the common name matted sandmat. It is native to South America but it can be found on most continents as an introduced species and often a weed. This is an annual herb forming a mat of prostrate stems which root at nodes where the stem comes in contact with the ground. The oval leaves occur in oppositely arranged pairs, each leaf less than a centimeter long. The inflorescence is a cyathium with scalloped white petal-like appendages surrounding the actual flowers. A red nectar gland is at the base of each appendage, and at the center of the cyathium are several male flowers around one female flower. The fruit is a lobed, spherical capsule.