Longleaf summer bluet

Houstonia longifolia, the long-leaved summer bluet, is a slender perennial herb in the bedstraw family Rubiaceae. The plant rises from a basal rosette of leaves on upright, wiry stems generally reaching about 20 cm but sometimes taller, with the basal foliage withering before flowering begins. Stem leaves are narrow, linear-lanceolate to oblong, opposite and entire, set off by a pair of small bristle-tipped stipules at each node. From late spring into summer the stems are tipped with branching cymes of small, four-lobed salverform flowers, typically white and sometimes faintly tinged with pink or lavender; the corolla tube is short and the lobes spreading. Fruits are tiny capsules splitting to release minute seeds. The species occupies upland woods in poor, dry, often sandy soils across most of eastern North America east of the Mississippi (except Delaware), extending west into the prairies and north into Canada from Quebec to Alberta; two varieties are recognised. Two recognised varieties differ in leaf width.