PlantaeDB Logo
Login Sign-up

Genus Pediomelum in Subfamily Papilionoideae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Pediomelum (Rydb.) is a genus of herbaceous to slightly woody legumes belonging to the Fabaceae, subfamily Papilionoideae, tribe Psoraleeae. Current checklists list about nine species (POWO, 2024; WFO, 2024). The genus is confined to temperate North America, ranging from the northern Great Plains through the intermountain West to desert basins of the Southwest. Typical habitats include mixed‑grass prairie, sagebrush steppe and open desert scrub; many taxa occupy elevations from 600 m to over 3 000 m. The type species is Pediomelum cuspidatum (Pursh) Rydb., designated in the original description (Rydberg, 1916).

Morphologically, Pediomelum is characterised by a taprooted perennial habit and pinnately compound leaves with three to five leaflets bearing a central vein. Stipules are reduced to small sheath‑like structures or absent. Inflorescences are terminal or axillary spikes; papilionaceous flowers have a broad standard, two spreading wings and a usually curved keel. The superior ovary is unilocular with a single ovule, and the mature fruit is a leathery, indehiscent legume containing one seed with a hard coat.

Species richness is greatest in the central United States, with several narrow endemics. Pediomelum reverchonii occurs only on the Edwards Plateau of Texas, while Pediomelum digitatum is confined to the Chihuahuan Desert. These taxa typically occupy open, well‑drained soils and can persist after fire or grazing disturbance.

Pollination is melittophilous; visits by native bees such as Melissodes spp. are frequent (Lewis & Schrire, 2021). Seed dispersal is primarily ballistic or through ingestion by herbivores; germination is enhanced after scarification. Chromosome counts of 2n = 20 have been reported for several species, indicating a base number of x = 10 (Egan et al., 2019).

Historically Pediomelum was treated as a section within Psoralea, but recent molecular phylogenies resolve it as a distinct, monophyletic clade sister to Psoralidium (Egan et al., 2019). Most modern floras accept Pediomelum at generic rank, although some regional treatments retain certain taxa under Psoralea (e.g., Pediomelum esculentum as Psoralea esculentum in certain US manuals). This divergence reflects ongoing debate on circumscription and warrants further taxonomic revision.

Human relevance is limited; Pediomelum spp. are occasionally cultivated as drought‑tolerant ornamentals, and the taproot of Pediomelum esculentum was historically important to Indigenous peoples. None of the species are regarded as significant weeds or invasive.

Several narrow endemics are listed as threatened at the state level because of habitat loss and overgrazing. Further demographic monitoring and seed‑bank studies will be essential for conservation (POWO, 2024).

Pick a Species to see its components: