Centrosema virginianum

Centrosema virginianum
Photo by Gil Nelson
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta - Flowering plants
Class:	Magnoliopsida – Dicotyledons
Order:	Fabales
Family:	Fabaceae ⁄ Leguminosae
Genus:	Centrosema
Species:	C. virginianum
Binomial name
Centrosema virginianum (L.) Benth.
Natural range of Centrosema virginianum from USDA NRCS Plants Database.

Common name: Spurred Butterfly Pea

Description

Centrosema virginianum is a perennial herbaceous vine. It grows as a twining vine, climbing on Smilax vines and low vegetation, frequently appearing among grasses (FSU Herbarium).

Centrosema virginianum is seen growing in a tailing, climbing, and twining fashion. The plant is a perennial herbaceous vine that grows 0.5-1.5 m long, and is more or less minutely pubescent throughout. The leaves are 3-foliolate; the leaflets are widely to narrowly ovate, ovate-lanceolate or oblong to elliptic, are conspicously reticulate, mostly growing 2-7 cm long, and are stipellate. The stipules are ovate-lanceolate to lanceolate, striate, persistent, 1.5-4 mm long. The racemes are with peduncles usually growing 1-5 cm long, the zig-zag rachis bears 1-4 nodes each with an ovate bract growing up to 1.5-3 cm long subtending a pedicel (growing 2-10 cm long) surmounted by 2 ovate bractlets growing 0.8-1.2 cm long. The calyx is somewhat hidden by the braclets, the tube is broadly hemispheric, growing 4-5 mm long, the lobes are linear-subulate, growing 0.6-1.4 cm long, the lowermost longest. The petals are pale blue-violet to lavender in color, growing 2.5-3.5 cm long, is spurred near the base, the wigs and keel are nearly equal in size, ca. 2 cm long. The stamens are diadelphous, 9 and 1. The legume is linear, flattened, and grows 7-14 cm long and ca. 4 mm broad, is subsessile, many seeded with an elongate, persistent, beak-like style, valves longitudinally twisting after dehiscence (Radford 1964).

Ecology

It is a legume that has one of the highest nitrogen-fixing potentials (Cathey et al 2010). Because of this, it may be able to help restore N lost from fire (Hainds et al 1999). By mid-season in June and July, a maximum nitrogen-fixing rate was observed (Cathey et al 2010).

Habitat

It is found in a wide range of natural and disturbed conditions, including frequently burned sandhills, upland longleaf-wiregrass and old-field pinelands (Cushwa 1966, Hainds 1999), and flatwoods, coastal island dunes and shorelines, open areas within mangrove swamps, wooded floodplains and edges of hardwood forests, and bogs . It can be found in loblolly pine communities (Cushwa 1966). It can also be found in longleaf pine-wiregrass communities (Hainds et al 1999). It is tolerant of overstory canopies that decrease the light level to about half the ambient (i.e., it can live in partially shaded areas and its nitrogen-fixing capability won't be significantly affected) (Cathey et al 2010). It grows in highly disturbed areas, but it is also ubiquitous in high quality native longleaf pine uplands and sandhills. It occurs in soils ranging from deep sands (Entisols) to sandy loams (Ultisols).

Associated species includes Blackberry Bramble, turkey oak, longleaf pine, Galactia, Strophostyles, Smilax, Penstemon, Lechea, Chrysopsis, Brumelia, Centrosema, Euphorbia, Cassia, Serenoa repens, Quercus incana, Quercus chapmanii, Diospyros, Aristida, Andropogon, bahia grass, Rubus, cloverleaf, Pinus taeda, Liquidambar styraciflua, and others (FSU Herbarium).

Phenology

It flowers in April through October and fruits primarily in June thorugh September (FSU Herbarium).

Seed bank and germination

In Hier's study, changes in flowering did not seem to affect seed germination (Hiers et al 2000). It spreads clonally by production of rhizomes (Hiers et al 2007).

Fire ecology

It thrives under fire (Cushwa 1966). Hendricks observed that the Piedmont National Wildlife Refuge plots, which had been under a 4-year burning regime since 1966, each contained more than 10 times more C. virginianum individuals per ha than the Oconee National Forest plots, which had no burning history (Hendricks et al 1999). Seasonal burning does not seem to negatively affect nitrogen fixation (Hiers et al 2003). C. virginianum showed increased flowering synchrony in response to lightning-season burns (Hiers et al 2000). It responded the best to March burns with respect to annual tissue inputs as well as nitrogen contribution (Hiers et al 2003). C. virginianum showed robust flowering response to late winter/ early spring burns, supporting the response to March burns noted earlier. It has a mid-summer flowering peak (Hiers et al 2000). Also, Hiers found no evidence that increased flowering affects nitrogen-fixing capability (Hiers et al 2003).

Pollination

Its flower is highly specialized for pollination by large Hymenoptera (Spears 1987 cited by Hiers et al 2007). It requires bees for pollination to "trip" the pollen delivery mechanism. Pollinator-plant relationships appear to be robust to alteration in flowering phenology resulting from variation in season of burn (Hiers et al 2000).

Use by animals

Because C. virginianum is a legume, and legumes are high in protein and mineral content, a number of herbivores including but not limited to Gopherus polyphemus, white-tailed deer, and bob-white quail, consume it (Hainds et al 1999).

References and notes

Cathey, S. E., L. R. Boring, et al. (2010). "Assessment of N2 fixation capability of native legumes from the longleaf pine-wiregrass ecosystem." Environmental and Experimental Botany 67: 444-450.

Cushwa, C. T. (1966). The response of herbaceous vegetation to prescribed burning. Asheville, USDA Forest Service.

Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: June 2014. Collectors: Loran C. Anderson, John C. Ogden, Gwynn W. Ramsey, R.K. Godfrey, R. S. Mitchell; R. C. Phillips, K. Craddock Burks, Gary R. Knight, D. W. Mather, C. Jackson, D. B. Ward, Mary Margaret Williams, O. Lakela, Brenda Herring, Jame Amoroso, Gwynn W. Ramsey, Richard Mitchell, Gail A. Steverson, Grady W. Reinert, George R. Cooley, R. J. Eaton, R. Kral, Cecil R Slaughter, Andre F. Clewell, R. Komarek, R. F. Doren, Kevin Oakes, Richard Gaskalla, Lisa Keppner, Clarke Hudson, Wilbur H Duncan, Jean Wooten, H. R. Totten, R. L. Wilbur, C. Ritchie Bell, Delzie Demaree, F. S. Earle, A. B. Seymour, Samuel B. Jones, Jr., H. R. Reed, A. B. Seymour, Michael B. Brooks, Sidney McDaniel, D. C. Bain, D. S. Correll, H. B. Correll, Lloyd H. Shinners, Geo M. Merrill, and H J Hamby. States and Counties: Alabama: Baldwin. Arkansas: Little Rock. Florida: Bay, Citrus, Collier, Duval, Escambia, Franklin, Gadsden, Gulf, Hillsborough, Jackson, Jefferson, Leon, Liberty, Manatee, Marion, Okaloosa, Polk, St Johns, St. Lucie, Suwannee, Wakulla, and Washington. Georgia: Bartow, Grady, Madison, and Thomas. Mississippi: Forrest, Harrison, Jackson, Pearl River, and Pike. North Carolina: Alamance, Orange, and Wilkes. Texas: Angelina, Bastrop, Freestone, Harris, Morris, Tarrant, and Van Zandt.

Hainds, M. J., R. J. Mitchell, et al. (1999). "Distribution of native legumes (Leguminoseae) in frequently burned longleaf pine (Pinaceae)-wiregrass (Poaceae) ecosystems." American Journal of Botany 86: 1606-1614.

Hendricks, J. J. and L. R. Boring (1999). "N2-fixation by native herbaceous legumes in burned pine ecosystems of the southeastern United States." Forest Ecology and Management 113: 167-177.

Hiers, J. K., R. Wyatt, et al. (2000). "The effects of fire regime on legume reproduction in longleaf pine savannas: is a season selective?" Oecologia 125: 521-530.

Hiers, J. K., R. J. Mitchell, et al. (2003). "Legumes native to longleaf pine savannas exhibit capacity for high N2-fixation rates and negligible impacts due to timing of fire." New Phytologist 157: 327-338.

Hiers, J. K. and R. J. Mitchell (2007). "The influence of burning and light availability on N-2-fixation of native legumes in longleaf pine woodlands." Journal of the Torrey Botanical Society 134: 398-409.

Spears, Jr. E. E. 1987. Island and mainland pollination ecology of Centrosema virginianum and Opuntia s trie ta. J. Ecol. 75: 351-362.