Perennial herb with fibrous roots 10 - 30 cm tall Leaves: opposite, stalkless, 1 - 3 cm long, 2 - 5 mm wide, broadly linear to narrowly oblong with a narrowed base, one-veined, hairless or nearly so. Inflorescence: a terminal cluster (cyme) of many small flowers. Flowers: short-stalked, purplish to white, 5.5 - 9 mm long, funnel-shaped, hairy within, with four lobes. The tube is twice as long as the lobes. Stamens included or barely exserted. Style one, stigmas two. Fruit: a small, dehiscent capsule, 2.5 - 3.5 mm wide, more or less spherical. Stems: numerous, slender, unbranched or branched above, sometimes finely hairy.
Similar species: Houstonia purpurea is similar but its lower leaves are three- to five-veined.
Flowering: May to July
Habitat and ecology: Local on limestone glades and gravelly sites. Typical of rocky woods, fields, and prairies in dry soil.
Occurence in the Chicago region: native
Etymology: Houstonia is named after Dr. William Houston (1695-1733), a Scottish-born surgeon and botanist who collected plants in Mexico and the West Indies. Longifolia means "long leaves."