Centrosema virginianum (L.) Benth.

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Leguminosae

Synonyms

Clitoria virginiana L.; Bradburya virginiana (L.) Kuntze; Glycine pugiunculus Desv.
Common names
Virginian centro (Australia), wild blue vine, bluebell and wild pea (Barbados).
Description
A climbing, herbaceous, perennial vine. Stems slender, 29 to 160 cm long, trailing and usually vigorously twining. Leaves alternate, pinnately trifoliate, 3 to 10 cm long. Stipules lanceolate or ovate, 1 to 4 mm long, setaceous and often deciduous. Petiole 2 to 5 cm long. Leaflets quite variable, linear to ovate to oblong or lanceolate-oblong, acute or acuminate at the apex, rounded at the base, usually 2 to 6 and sometimes 1 to 8 cm long, 1 to 2.5 cm wide, glabrous or nearly so.
Inflorescence a short raceme of one to four flowers on axillary peduncles, usually shorter than the foliage. Calyx deeply five-lobed, the acute lobes longer than the tube. Corolla purplish or lavender-blue to nearly white. Standard 2.5 cm long and 3 cm wide. Pods linear, 8 to 12 cm long, 3 to 4 cm wide; valves coriaceous, tordate, ribbed near the margin; beak up to 1 cm long. Four to ten seeds, dark brown or black, 2 mm long, with a small hilum (Gooding, Loveless and Proctor, 1965; Correll and Johnston, 1970; Pulle, 1976). Variable in leaflet size and shape and corolla colour. Often confused with C. pubescens but less robust.
Distribution
One of the most widely naturally distributed species of Centrosema, C. virginianum occurs more or less continuously from Uruguay and northern Argentina to the eastern United States and Bermuda in tropical and subtropical areas. It is found throughout the West Indies and has become naturalized in tropical West Africa.
Rainfall requirements
Most widely collected from subhumid (500 to 1 000 mm rainfall) and subtropical areas. Occasionally collected from semi-arid, tropical areas in Brazil, but rarely found in the wet tropics.
General features
C. virginianum is genetically very variable, especially in agronomic features such as vigour, flowering behaviour, frost resistance and drought resistance. It may be useful in subtropical pastures, though to date no natural accessions suitable for use in commercial pastures have been identified in Australia. Overall, it is more drought resistant than C. pubescens but less tolerant of waterlogging.
In Australia, it has been grown in both moderately acid sandy soils (pH 5.3 to 5.5) and alkaline clays (pH 6.5 increasing to 9 at depth). Inoculation with commercial centro rhizobium has always ensured nodulation.
In vitro digestibility of the leaves has been assessed at 54 to 59 percent, similar to that of siratro. Digestibility of the stem is somewhat lower (Clements et al., 1983) .
Main references
Clements (1983); Clements et al. (1983).
Latitudinal limits
Occurs naturally from 35°S to 40°N latitude.