Houstonia nigricans (Lam.) Fern. - Glade Bluets

Houstonia nigricans plant

Family - Rubiaceae

Stems - To 30cm tall, multiple from base, from taproot, erect, herbaceous, 4-angled, glabrous, dichotomously branching.

Leaves - Opposite, sessile, linear, glabrous to scabrous, entire, to +3cm long, 3mm broad, acute.

Houstonia nigricans leaves

Stipule at base of leaves.

Inflorescence - Flowers many near apex of stems forming a corymbiform cyme. Each division of inflorescence subtended by a pair of foliaceous bracts (reduced leaves).

Houstonia nigricans inflorescence

Flowers - Corolla 4-lobed, white. Tube to 3.3mm long, glabrous externally, densely pubescent internally. Lobes spreading, glabrous externally, densely pubescent internally, to 3mm long. Stamens 4, alternating with corolla lobes, adnate at apex of corolla tube. Filaments to 1mm long, whitish. Anthers -2mm long, blue-purple. Style glabrous, 2.7mm long, greenish-white. Hypanthium to 1.1mm long, glabrous. Sepals lanceolate,  acute, 1.6mm long, with few marginal cilia near base or not.

Houstonia nigricans flowerTypical flower.

Houstonia nigricans flowerThree-lobed flower.

Flowering - May - October.

Habitat - Dry exposed areas of loess hills, rocky ledges, limestone bluffs and glades.

Origin - Native to U.S.

Other info. - This plant is compact, densely branched, and produces many flowers. It is really an attractive little plant. It can be found in the Ozark section of the state north to a few eastern counties that border the Missouri river. H. nigricans is absent from most of the northern part of the state but reappears in a few northwest counties where the loess hills are found.
A synonym is Hedyotis nigricans (Lam.) Fosb.

Photographs taken in the Ozark Scenic Riverways, Shannon County, MO., 6-21-03 and 6-28-03, and in Shannon County, MO., 6-17-05.


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