| Author | Schubert | |
| Distribution | Throughout the Mountains and Piedmont, and present over most of the Coastal Plain, but likely absent in the eastern counties. Possibly under-collected over most of the Coastal Plain, or genuinely less widespread there.
Throughout the eastern U.S., ranging from ME and IA south to northern FL and to LA. | |
| Abundance | Common and widespread in the Mountains and Piedmont; fairly common in the western and central portions, but scarce in the eastern, where probably not truly absent. | |
| Habitat | This species has typical Desmodium habitats -- borders of dry woods, opening in woods, old fields, powerline clearings, and other brushy or disturbed places, usually in dry soil. A 2020 population in the Piedmont of Moore County occupied the base of creekside ledges. | |
| Phenology | Blooms from July to September, and fruits from August to October. | |
| Identification | This species and D. glabellum are the two most typical yet most difficult species to separate in NC. It has an erect stem, growing to about 3 feet tall. Unlike with D. glabellum, this species has quite densely hairy stems (pilose), including uncinate (hooked) hairs, as opposed to somewhat smooth in D. glabellum, which often has some uncinate hairs but is not densely hairy. The standard 3 leaflets are ovate in shape with rounded tips, the terminal one being 2-2.5 inches long and about 3/4 as wide; the lateral leaves are only slightly smaller. The leaf surfaces are quite pubescent as well. It has several panicles of flowers, with each flower being pink to purplish and about 1/4-inch long. This is a species you will encounter quite often over most of the state, and it and D. glabellum are usually identified first using "process of elimination", and then carefully checking the pubescence of the stem (and leaf petioles). Isely (1990) states: "D. perplexum is identified most readily by its several-segmented loments with ventrally angled articles that are combined with its usually pilose stems." He also states that for the very similar D. glabellum: "in general appearance, it usually most closely resembles D. perplexum, with which it is confluent [occurs in the same area], but typically has uncinate stem pubescence rather than the pilose inducement of the latter." Note that D. nuttallii can look somewhat similar, especially in leaflet shape, but that species has quite uncinate leaf surfaces (hooked hairs and a somewhat velvety look) so that the leaf can stick to clothing like Velcro. | |
| Taxonomic Comments | This species has variously been sunken into other species over the last 50 or more years, such as D. paniculatum or D. glabellum. Some references call (or called) it as D. dillenii.
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| Other Common Name(s) | Perplexing Tick-trefoil | |
| State Rank | S5 | |
| Global Rank | G5 | |
| State Status | | |
| US Status | | |
| USACE-agcp | | |
| USACE-emp | | |
