Thymus serpyllum is a perennial her; stems creeping, hairy, woody at base, rooting at nodes, branching, forming mats; inflorescence stems erect to 10 cm long.
Leaves opposite, usually elliptic, to 1 cm long, short-stalked.
Flowers purple, to 0.6 cm, bilaterally symmetrical, tubular, 2-lipped, upper lip flat, lower lip 3-lobed, slightly longer than upper, calyx 2-lipped, 5-lobed to 0.4 cm, stamens longer than petal lobes, inflorescence spikes at ends of stems to 4 cm, June-Sept.
Fruit dry nutlets.
Wetland status: NL.
Frequency in NYC: Very infrequent.
Habitat: Escaped from cultivation. Upland woods and fields.