Trichostema dichotomum is an annual herb to 70 cm tall (usually much less), slender, minutely glandular-hairy, branched.
Leaves opposite, to 6 x 2.5 cm, oblong to egg-shaped, tips blunt.
Flowers blue irregularly 5-lobed, lowest lobe longer than other 4, stamens blue, much longer that petal lobes, filaments to 1.5 cm, arching upward and curled back, calyx tubular irregularly 5-lobed, longest teeth are lowest, to 0.5 cm, becoming 0.9 in fruit, Aug.-Sept..
Fruit dry nutlets to 0.3 cm.
Wetland status: UPL.
Frequency in NYC: Very infrequent.
Habitat: Open, dry, soil, old fields, open woods, open dry, disturbed soil.