Houstonia longifolia Gaertn.

Long-Leaved Bluets

Houstonia longifolia plant

Family - Rubiaceae

Stems - Multiple from fibrous roots or small caudex, to 25cm tall, simple or branching above, herbaceous, 4-angled, glabrous, often reddish below.

Leaves - Basal leaves petiolate. Petioles to +1cm long. Blades oblong to spatulate or lanceolate, tapering at base, glabrous, reddish below, green above. Cauline leaves sessile, opposite, 3cm long, +/-5mm broad, antrorse strigose, entire, linear to narrowly oblong. Opposing leaves joined at base by whitish stipule. Stipule 3mm long, 2mm broad, triangular, with few coarse purplish teeth on margins or entire.

Houstonia longifolia stipuleLeaf stipule.

Inflorescence - Loose cymes of +/-3 flowers terminating stems. Pedicels to 4mm long, -1mm in diameter, appearing glabrous but heavily glandular (need lens to see).

Flowers - Corolla pinkish to white, funnelform, , 4-lobed, glabrous externally, to 7mm long. Lobes 2mm long and broad, acute or minutely mucronate (mucronulate), pubescent internally, distinctly one-nerved. Stamens 4, adnate near base of corolla tube. Anthers pale-yellow, -1mm long. Filaments very short (.1mm long). Style filiform, glabrous, 6-7mm long, slightly exserted. Stigmas 2, globose. Hypanthium 1mm long. Calyx lobes to 3mm long, glabrous, entire, subulate. Fruit globose, to -3mm in diameter.

Houstonia longifolia calyxCalyx.

Houstonia longifolia flowerCorollas.

Flowering - April - July.

Habitat - Rocky open woods, prairies, glades, bluff ledges.

Origin - Native to U.S.

Other info. - In Missouri this little plant can basically be found in all counties east of a line drawn from Barton County to Callaway County. The plant is common in the parts of the state where it grows.
H. longifolia is most common on acid soils whereas the similar H. nigricans (Lam.) Fern. is more typically found on basic substrata.
A common synonym is Hedyotis longifolia (Gaertn.) Hook.

Photographs taken on Taum Sauk Mountain, MO., 5-31-03.