Oneleaf Senna

Sericeocassia uniflora (Mill.) Britton
Cassia ttniflora Mill. Diet. Gard. ed. 8. no. 5. 1768. Cassia ornithopoides Lam. Encyc. 1: 644. 1785. Cassia sericea Swartz, Fl. Ind. Occ. 724. 1788. Cassia sensiiiva Jacq. Coll. 2: 362. 1788. Cassia ciliata Hoffm.; DC. Prodr. 2: 493. 1825. Cassia monantha DC. Prodr. 2: 506. 1825.
Appressedvillous with brownish long hairs, simple or branched, 3-10 dm. high. Stipules narrowly linear, 5-20 mm. long; leaves 6-15 cm. long, petioled, bearing long-stalked glands between one or more of the pairs of leaflets; leaflets 2-4 pairs, thin, nearly sessile, oblong to obovate, 2-5 cm. long, rounded or acutish and mucronate at the apex, rounded or narrowed at the base, glabrate above, appressed-siUcy beneath; peduncles as long as the petioles or shorter; sepals rounded, about 6 mm. long; petals about twice as long as the sepals; legume 2.5-5 cm. long, about 4 mm. wide, compressed.
Typb locality: Campeche.
Distribution: Jamaica; Bahamas; Cuba; Hispaniola; Sonora and San Luis Potosi to El Salvador. Venezuela. Galapagos.

Annual, Herbs, Stems woody below, or from woody crown or caudex, Stems erect or ascending, Stems or branches arching, spreading or decumbent, Stems less than 1 m tall, Stems solid, Stems or young twigs sparsely to densely hairy, Stem hairs hispid to villous, Leaves alternate, Leaves petiolate, Extrafloral nectary glands on petiole, Stipules inconspicuo us, absent, or caducous, Stipules setiform, subulate or acicular, Stipules deciduous, Stipules free, Leaves compound, Leaves even pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 5-9, Leaflets 10-many, Leaves hairy on one or both surfaces, Flowers in axillary clusters or few-floweredracemes, 2-6 flowers, Inflorescences racemes, Inflorescence axillary, Bracts very small, absent or caducous, Flowers actinomorphic or somewhat irregular, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Petals orange or yellow, Fertile stamens 6-8, Stamens heteromorphic, graded in size, Stamens completely free, separate, Filaments glabrous, Anthers opening by basal or terminal pores or slits, Style terete, Fruit a legume, Fruit stipitate, Fruit unilocular, Fruit freely dehiscent, Fruit elongate, straight, Fruit oblong or ellipsoidal, Fruit exserted from calyx, Fruit compressed between seeds, Fruit hairy, Fruit 11-many seeded, Seed with elliptical line or depre ssion, pleurogram, Seeds ovoid to rounded in outline, Seeds subquadrate, Seed surface smooth, Seeds olive, brown, or black.

Senna uniflora, the oneleaf senna, is a species of flowering plant in the family Fabaceae. It is native to Mexico, Central America, the Caribbean, Colombia, Venezuela, and most of Brazil, and has been introduced to India, Mauritius, and Réunion. Although it is somewhat weedy and invasive, it is used to out-compete the pernicious weed Parthenium hysterophorus.