Desmodium is a genus in the flowering plant familyFabaceae, sometimes called tick-trefoil, tick clover, hitch hikers or beggar lice. There are dozens of species and the delimitation of the genus has shifted much over time. These are mostly inconspicuous legumes; few have bright or large flowers. Though some can become sizeable plants, most are herbs or small shrubs. Their fruit are loments, meaning each seed is dispersed individually enclosed in its segment. This makes them tenacious plants and some species are considered weeds in places. They have a variety of uses, as well.
Uses
Several Desmodium species contain potent secondary metabolites that are released into the soil and aerially. Allelopathic compounds are used aggressively in agriculture in push-pull technology: Desmodium heterocarpon, Desmodium intortum, and Desmodium uncinatum are inter-cropped in maize and sorghum fields to repel Chilo partellus, a stem-boring grass moth, and suppress witchweeds, including Asiatic witchweed and purple witchweed. High amounts of antixenotic allomones produced by Desmodium also repel insect pests. Different Desmodium species produce different profiles of organic compounds through their root systems. The reasons for the production of these compounds that have benefited cereal crop production are however unknown, as they don't seem to serve any apparent function to the plant itself. Tick-trefoils are also useful as living mulch and as green manure, as they are able to improve soil fertility via nitrogen fixation. Most also make good fodder for animals including bobwhite, turkey, grouse, deer, cattle and goats. Some Desmodium species have been shown to contain high amounts of tryptamine alkaloids, though many tryptamine-containing Desmodium species have been transferred to other genera. The caterpillars of the lesser grass blue and the two-barred flasher feed on tick-trefoils. Deer also appear to rely on some species in certain areas, particularly during the more stressful summer months.
The taxonomy and systematics of the many dozens of Desmodium species are confusing and unresolved. Related genera such as Codariocalyx, Hylodesmum, Lespedeza, Ohwia, and Phyllodium were and sometimes still are included in Desmodium. Taxonomic authorities commonly disagree about the naming and placement of species. For example, Desmodium spirale as described by August Grisebach might refer to a distinct species, but its validity is doubtful. The "Desmodium spirale" of other authorities may refer to D. neomexicanum, D. ospriostreblum, or D. procumbens. Similarly, the plant originally described as D. podocarpum by A. P. de Candolle is Hylodesmum podocarpum today, but "Desmodium podocarpum" might also refer to D. hookerianum or Hylodesmum laxum, depending on the taxonomic authority.
