A large and complex Eurasian genus, the species often misidentified and with tendencies to hybridize. Thymus vulgaris L. is the common herb; it has ± tomentose leaves with revolute margins. Thymus serpyllum L. with stems pubescent on all sides is rarely cultivated in North America; most garden plants (as well as escapes) are other species, including the two below.

1. Stem ± terete, pubescent on the entire surface; leaves ± linear, with weak lateral veins.

T. albidus

1. Stem 4-angled, pubescent entirely or primarily on the angles; leaves elliptic to somewhat spatulate, with strong lateral veins beneath.

T. pulegioides