Lamium purpureum is a winter annual herb 10-40 cm tall, usually branched from base, lower part of stem often prostrate, stem 4-sided, usually purplish, lower internodes elongate.
Leaves opposite, stalked, blade 0.7-3 cm long, heart-shaped, surface dull, finely bristly, puckered by sharply impressed veins, margin toothed; the upper blades usually purplish, crowded near top of stem, especially those of the inflorescence.
Flowers pale purple, tubular, bilaterally symmetrical, 1-1.5 cm long, hairy outside, upper lip 0.2-0.4 cm long, hood-like, calyx 0.5-0.6 cm long, purplish, lobes linear, bristly; flowers in whorls of 3-6 in upper leaf axils; blooming and fruiting April-Oct. Pollinated by bees (Lovell 1918).
Fruit dry nutlets 0.2 cm long.
Wetland status: UPL.
Frequency in NYC: Infrequent in natural areas.
Habitat: Mostly a lawn, garden, and agricultural weed.