It is an annual plant that grows from 5 to 27 cm tall. The obovate or elliptical leaves, about 6-14 per plant, are scattered along the elongate, glabrous stem and are generally 3.5-8.5 mm long and 0.8-2.5 mm wide. Scapes are absent.
S. tenellum is endemic to Southeast Asia and its distribution ranges from southern India to southern China and south to Sumatra. In China it's known from Guangdong, Yunnan, and southern Fujian provinces. Its habitat is recorded as being seasonal swamps and is often reported to grow near rice paddies.