Stylosanthes biflora (L.) BSP.

Pencil Flower

Stylosanthes biflora plant

Family - Fabaceae

Stems - Multiple from the base, from a taproot, erect to ascending, herbaceous, branching, to +/-30cm long, with long antrorse appressed trichomes and erect needle-like erect pubescence. The erect trichomes are red when viewed with a lens.

Stylosanthes biflora stem

Leaves - Alternate, petiolate, trifoliolate, stipulate. Stipules to 3mm long, linear, ciliate-margined. Lateral leaflets sessile, oblong, entire, to +/-2cm long, +/-6mm broad, sparse ciliate above and below, deep green above, lighter green below. Lateral venation shiny when hit with light. Terminal leaflet stalked, slightly larger or equal to lateral leaflets. All leaflets typically mucronate.

Stylosanthes biflora leavesPressed leaves.

Inflorescence - Single flowers in the axils of the apical leaves.

Flowers - Corolla papilionaceous, yellow-orange. Standard to 9mm broad, 6mm broad. Wings to -5mm long. Stamens monodelphous. Anthers unequal. Calyx tube campanulate, green, bilabiate. Upper lobe single-lobed, notched at the apex, to 1.8mm long. Lower lip 3-lobed. Central lobe to 3mm long. Lateral lobes to 1.5mm long. All lobes attenuate. Loments of 2 unequal segments.

Stylosanthes biflora calyxCalyx.

Stylosanthes biflora flower

Flowering - May - September.

Habitat - Rocky open woods, glades, prairies, usually on acid substrates.

Origin - Native to U.S.

Other info. - This little species can be found mainly in the southern 1/2 of Missouri. The plant is easy to ID in the field but is often overlooked because of its small size.

Photographs taken in the Croatan National Forest, NC., 7-17-02, and off Hwy 106, Shannon County, MO, 6-6-03.