|Photo taken by Kevin Robertson|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida – Dicotyledons|
|Family:||Fabaceae ⁄ Leguminosae|
| Desmodium obtusum|
(Muhl. ex Willd.) DC.
|Natural range of Desmodium obtusum from USDA NRCS Plants Database.|
Common name: Stiff tick-trefoil
Synonyms; Desmodium rigidum (Elliott) A.P. de Candolle; Meibomia rigida (Elliott) Kuntze
Generally, for Desmodium genus, they are "annual or perennial herbs, shrubs or small trees. Leaves 1-5 foliolate, pinnately 3-foliolate in ours or rarely the uppermost or lowermost 1-foliolate; leaflets entire, usually stipellate; stipules caduceus to persistent, ovate to subulate, foliaceous to setaceous, often striate. Inflorescence terminal and from the upper axils, paniculate or occasionally racemose; pedicel of each papilionaceous flower subtended by a secondary bract or bractlet, the cluster of 1-few flowers subtended by a primary bract. Calyx slightly to conspicuously 2-lipped, the upper lip scarcely bifid, the lower lip 3-dentate; petals pink, roseate, purple, bluish or white; stamens monadelphous or more commonly diadelphous and then 9 and 1. Legume a stipitate loment, the segments 2-many or rarely solitary, usually flattened and densely uncinated-pubescent, separating into 1-seeded, indehiscent segments." 
Specfically, for D. obtusum species, they are "erect perennial; stems 0.5-1.2 m tall, densely uncinate-pubescent. Terminal leaflets oblong to ovate or elliptic, (0.8) 2-3.5 (4.5) cm long, mostly 1,8-2.2 times as wide, short-puberulent to short-pubescent or glabrate above, sparsely to densely short-pubescent and reticulate below; stipules soon deciduous, lance-attenuate to ovate-lanceolate, 2-6 mm long; stipels persistent. Inflorescence usually paniculate, short-pubescent to pilose; petals purplish, ca. 4-6 mm long; stamens diadelphous. Loment of 1-4 weakly obovate to suborbicular segments, each 3-5 mm long, 2.5-2.5 mm broad, very slightly convex along the upper suture and broadly rounded below, densely uncinulate-puberulent on both sides and sutures; stipe about 1.5-3.5 mm long, longer than the calyx tube but shorter than the lobes and the stamina remnants." 
Found north to New Hampshire south to Florida and west to Colorado.
It is distributed widely throughout the eastern U.S. and southern Great Plains. Occurs in frequently burned longleaf and shortleaf pine-oak-hickory upland native and old-field communities (Ultisols), longleaf pine-turkey oak sandhills (Entisols), longleaf and slash pine flatwoods (Spodosols), and in limestone outcrops. It is fire-tolerant. Occurs in both native areas and areas with recent soil disturbance. Some seem to have ruderal-growing tendencies. Occurs on a wide range of soils from loamy sand to clayey soils; and in sites ranging from xeric to moist. Associated species include Desmodium glabellum and Gnaphalium obtusifolium.
In the southeastern coastal plain it flowers from September to October and fruits from September to November.
This species is thought to be dispersed by translocation on animal fur or feathers. 
It thrives in frequently burned (1-2 year interval) habitats and occurs primarily in high-light environments but can also tolerate partial shade.
Floral visitors include bumblebees (Bombus), longhorned bees (Melissodes spp.), and leaf cutter bees (Megachile spp.).
Use by animals
Insect feeders include skipper caterpillars as Achalarus lyciades (Hoary Edge), Thorybes bathyllus (Southern Cloudywing), Thorybes pylades(Northern Cloudywing), and Epargyreus clarus (Silver-Spotted Skipper); the caterpillars of the butterflies Everes comyntas(Eastern Tailed Blue) and Strymon melinus (Gray Hairstreak). Seeds are eaten by gamebirds (Bobwhite, Wild Turkey) and rodents (White-Footed Mouse, Deer Mouse). White-Tailed Deer and Cottontail Rabbits eat the foliage.
Conservation and management
Cultivation and restoration
References and notes
- 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. 604-10. Print.
- []NatureServe. Accessed April 21, 2016
- NRCS Plants Database http://plants.usda.gov/java
- Cushwa, C. T. (1970). Response of legumes to prescribed burns in loblolly pine stands of the South Carolina Piedmont. Asheville, NC, USDA Forest Service.
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: June 2014. Collectors: R.K. Godfrey, John Morrill, Loran C. Anderson, A. F. Clewell, R. Kral, J. P. Gillespie; D. C. Hunt, R. Komarek, Sidney McDaniel, Samuel B. Jones, Jr., Harry E. Ahles, J A Duke; Charles S. Wallis, William B. Fox, Lloyd H. Shinners, and Eula Whitehouse. States and Counties: Alabama: Greene and Macon. Florida: Calhoun, Escambia, Franklin, Jackson, Leon, Madison, and Wakulla. Georgia: Baker, Colquitt, Grady, and Thomas. Louisiana: Bossier. Mississippi: Lamar. North Carolina: Mecklenburg and Robeson. Oklahoma: Sequoyah. Texas: Freestone.
- 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.
- []Illinois Wildflowers. Accessed: April 21, 2016