Prairie bluets

Stenaria nigricans, the prairie bluets or diamondflower (formerly placed in Hedyotis and Houstonia), is a perennial herb in the Rubiaceae family native to the central and southern Great Plains and adjacent regions of the United States and northern Mexico. Plants form low cespitose clumps 10 to 40 centimetres tall arising from a slender woody base. Stems are wiry, four-angled, and much-branched, bearing opposite, linear to narrowly lanceolate leaves about one to three centimetres long with small interpetiolar stipules characteristic of the family. From late spring through autumn the plant produces numerous small, white to pinkish, salverform flowers with four spreading corolla lobes, each blossom about half a centimetre across, arranged in lax terminal cymes. Fruits are small two-lobed capsules containing several seeds. The species favours dry prairies, rocky slopes, and limestone outcrops on calcareous soils.