|Photo by Gil Nelson|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida – Dicotyledons|
|Family:||Fabaceae ⁄ Leguminosae|
|Natural range of Crotalaria purshii from USDA NRCS Plants Database.|
Common names: Pursh's rattlebox, coastal plain rattlebox
The Crotalaria genus, in general, are annual or perennial herbs or shrubs. The leaves can be simple or palmately 3-7 foliolate where the stipules are either lacking or are varying from minute to large and conspicuous and the leaflets are estipellate. The flowers are papilionaceous and are usually in terminal racemes but can but solitary. The bracts are subtending the pedicels are small to foliaceous, caduceus to persistent; the bracts are paired, minute to large borne on the pedicel or on the base of the calyx. The calyx is campanulate. The petals are yellow or yellow with purple streaks, they're rarely purple or blue; standard usually exceeding the wing and keel petal. There are 10 stamens, they are monadelphous, filaments of two lengths, the longer with small, subglobose anthers and the shorter with larger, linear anthers. The legume is inflated, few-many seeded, globose to more typically oblong-cylindric, sessile or rarely stalked.
Specifically, for Crotalaria purshii, the plant is a perennial herb, growing up to 2-5 dm tall. It is densely appressed pubescent. The leaves are simple, the median and upper leaves are mostly linear to lanceolate, growing 3-6 (8) cm long, and 4-10 mm wide, the lower leaves are oblong to spatulate, growing 2-3 cm long, and 6-15 mm wide. The stipules of the the median and upper leaves are inversely sagittate decurrent 1/2 the length of the internode or more. The peduncle grows to 3-12 cm long, and is 3-6 flowered. The calyx is closely subtended by 2 linear, appressed bractlets, growing 4-6 mm long. The petals are yellow in color, and are equal or longer than the calyx. The legume is glabrous, oblong-cylindric, growing 2.5-4 cm long, and ca. 1 cm in diameter.
The root system of Crotalaria purshii includes stem tubers which store non-structural carbohydrates (NSC) important for both resprouting following fire and persisting during long periods of fire exclusion. Diaz-Toribio and Putz (2021) recorded this species to have an NSC concentration of 230.7 mg/g (ranking 19 out of 100 species studied) and water content of 54.1% (ranking 17 out of 100 species studied).
Crotalaria purshii is endemic to the Southeastern Coastal Plain, ranging from southeast Virginia to north Florida, as well as central peninsular Florida and west to eastern Louisiana and other scattered locations more inland.
It is a legume.
C. purshii can be found in sandy openings, dry to mesic pinelands, and roadsides. It can live in temperatures ranging from 10 to 28 degrees Celsius with an average of 115 cm of rain annually. It appears in a range of light conditions, from semi-shade to full sun, and a variety of mostly sandy soil types, including drying loamy sand, moist sand, clayey soil, peat, and loose sand. Specific habitat includes grassy pineland communities such as loblolly pine communities, pine-scrub oak-palmetto woodlands, coastal dunes, and hillside bogs. It also can be found in disturbed areas, including roadsides and clobbered flatwoods. It is considered an indicator species of the upper panhandle savannas in Florida.
Associated species include Baptisia simplicifolia, Liatris, Vernonia, Pityopsis, Eupatorium mohrii, E. rotundifolium, Pinus palustris, Quercus marilandica, Andropogon, Panicum, Vaccinium, Aristida stricta, Sabal minor, Ilex glabra, and others.
Crotalaria purshii is an indicator species for the Upper Panhandle Savannas community type as described in Carr et al. (2010).
Crotalaria purshii was observed flowering in sandhill and flatwood forests.
This species is thought to be dispersed by ants and/or explosive dehiscence. 
This species is fire tolerant and occurs in burned areas. Populations of Crotalaria purshii have been known to persist through repeated annual burns. One study found C. purshii to significantly increase in frequency in response to fire, and to benefit mostly from winter and spring burn regiments rather than summer burns.
Herbivory and toxicology
It is consumed by bobwhite quail.
Conservation, cultivation, and restoration
This species is listed as endangered and possibly extirpated by the Tennessee Department of Environment and Conservation. The genus Crotalaria is also listed as a noxious weed by the Arkansas State Plant Board.
The seeds may be used as a substitute for coffee, but it is not recommended as improper preparation could result in poisoning.
References and notes
- Weakley, A.S. 2020. Flora of the Southeastern United States. Edition of 20 October 2020. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
- Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 584-5. Print.
- Diaz-Toribio, M.H. and F. E. Putz 2021. Underground carbohydrate stores and storage organs in fire-maintained longleaf pine savannas in Florida, USA. American Journal of Botany 108: 432-442.
- Weakley, A. S. (2015). Flora of the Southern and Mid-Atlantic States. Chapel Hill, NC, University of North Carolina Herbarium.
- Graham, E. H. (1941). Legumes for erosion control and wildlife. Washington, USDA
- Miller, J. H. and K. V. Miller (1999). Forest plants of the southeast, and their wildlife uses Champaign, IL, Southern Weed Science Society.
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: June 2014. Collectors: Harry E. Ahles, Loran C. Anderson, Grafton Anding, Wilson Baker, M.L. Bomhard, R. S. Campbell, Andre F. Clewell, Richard R. Clinebell II, D. S. Correll, Delzie Demaree, Robert K. Godfrey, J. Haesloop, A. Johnson, Lisa Keppner, Ed Keppner, R. Komarek, R. Kral Paul C Lemon, M. Jenkins, Sidney McDaniel, Thomas E. Miller, John B. Nelson, R. A. Norris, C.K. Pearse, A. B. Pittman, H. R. Reed, Annie Schmidt, Kenneth Lee Tyson, and Jean Wooten. States and Counties: Alabama: Baldwin, Conecuh, Geneva, and Washington. Florida: Bay, Calhoun, Dixie, Duval, Franklin, Gadsden, Gulf, Lee, Leon, Liberty, Madison, Santa Rosa, Sarasota, Wakulla, Walton, and Washington. Georgia: Berrien, Coffee, Grady, Seminole, Thomas, and Tift. Louisiana: Washington. Mississippi: George, Jackson, and Pearl River. North Carolina: Sampson. South Carolina: Dorchester and Lee.
- Carr, S. C., et al. (2010). "A Vegetation Classification of Fire-Dependent Pinelands of Florida." Castanea 75(2): 153-189.
- Carr, S.C., K.M. Robertson, and R.K. Peet. 2010. A vegetation classification of fire-dependent pinelands of Florida. Castanea 75:153-189.
- Platt, W. J., Gregory W. Evans, and Mary M. Davis (1988). "Effects of Fires Season on Flowering of Forbs and Shurbs in Longleaf Pine Forests." Oecologia 76(3): 353-363.
- Nelson, G. PanFlora: Plant data for the eastern United States with emphasis on the Southeastern Coastal Plains, Florida, and the Florida Panhandle. www.gilnelson.com/PanFlora/ Accessed: 8 DEC 2016
- Kirkman, L. Katherine. Unpublished database of seed dispersal mode of plants found in Coastal Plain longleaf pine-grasslands of the Jones Ecological Research Center, Georgia.
- Robertson, K.M. Unpublished data collected from Pebble Hill Fire Plots, Pebble Hill Plantation, Thomasville, Georgia.
- Kush, J. S., et al. (2000). Understory plant community response to season of burn in natural longleaf pine forests. Proceedings 21st Tall Timbers Fire Ecology Conference. Fire and forest ecology: innovative silviculture & vegetation management, Tallahassee, FL, Tall Timbers Research, Inc.
- USDA, NRCS. (2016). The PLANTS Database (http://plants.usda.gov, 22 April 2019). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- Fernald, et al. 1958. Edible Plants of Eastern North America. Harper and Row Publishers, New York.