Desmodium
Desmodium is a genus of plants in the legume family Fabaceae, 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. Species are distributed widely – from Quebec to northern Argentina in the Americas, across northern and southern tropical Africa, in the southern Arabian Peninsula, in Myanmar and Thailand, New Guinea, and northern and eastern Australia.

Description

These are mostly inconspicuous plants; 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.

Uses 
Several Desmodium species release organic compounds, aerially and into the soil, which make them useful for agriculture: 
Allelopathic compounds are used there via push-pull technology. For this Desmodium heterocarpon, Desmodium intortum, and Desmodium uncinatum are inter-cropped in maize and sorghum fields to suppress witchweeds, including Asiatic witchweed (Striga asiatica) and purple witchweed (S. hermonthica) and to repel Chilo partellus, a stem-boring grass moth. Insects (including pests) are likewise repelled by  high amounts of antixenotic allomones produced by Desmodium.

Tick-trefoils in agriculture can also be used as living mulch and as green manure, as they improve soil fertility via nitrogen fixation. 
 
Most also make good fodder for animals including bobwhite, turkey, grouse, deer, cattle and goats.

Wild-living, non-farmed deer appear to rely on Desmodium species in certain areas, particularly during the more stressful summer months.

The caterpillars of the lesser grass blue (Zizina otis) and the two-barred flasher (Astraptes fulgerator) feed on tick-trefoils.

Alkaloids
Some Desmodium species have formerly been known to contain high amounts of tryptamine alkaloids, but many of the tryptamine-containing species have since been transferred to other genera.

Taxonomy and systematics
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.

Selected species

Species include: Dietrich Brandis (1874): Illustrations of the Forest Flora of North-West and Central India.
 Desmodium acanthocladum F.Muell.
 Desmodium canadense (L.) DC. – showy tick-trefoil, Canadian tick-trefoil
 Desmodium canescens (L.) DC. – hoary tick-trefoil
 Desmodium ciliare (Muhl.) DC. – hairy small-leaved tick-trefoil
 Desmodium cuspidatum (Muhl.) Loudon – toothed tick-trefoil, large-bracted tick-trefoil
 Desmodium glabellum (Michx.) DC.
 Desmodium heterocarpon (Michx.) DC. – Asian tick-trefoil
 Desmodium × humifusum (Muhl. ex Bigelow) Beck 
 Desmodium illinoense A.Gray – Illinois tick-trefoil
 Desmodium incanum (Sw.) DC. – creeping beggarweed, Spanish tick-trefoil, Kaimi clover
 Desmodium intortum Greenleaf desmodium, kuru vine, beggarlice, tick clovers
 Desmodium lineatum (Michx.) DC. – linear-leaved tick-trefoil
 Desmodium marilandicum (L.) DC. – smooth small-leaved tick-trefoil

 Desmodium ospriostreblum Chiov.
 Desmodium paniculatum (L.) DC. – panicled tick-trefoil
 Desmodium perplexum B.G.Schub. – perplexed tick-trefoil
 Desmodium rotundifolium DC. – round-leaved tick-trefoil, dollar leaf
 Desmodium triflorum (L.) DC.
 Desmodium tweedyi Britton – Tweedy's tick-trefoil
 Desmodium uncinatum (Jacq.) DC.– silver-leaved tick-trefoil, silverleaf
 Desmodium varians (Labill.) G.Don

Formerly placed here
 Codariocalyx motorius – telegraph plant (as D. gyrans, D. motorium, D. roylei)
 Dendrolobium triangulare (as D. Desmodium umbellatum Moritz.)
 Dendrolobium umbellatum (as D. umbellatum  (L.) Benth. )
 Hylodesmum laxum (as D. laxum DC.)
 Hylodesmum laxum ssp. laxum (as D. austro-japonense, D. bambusetorum, D. gardneri auct. non Benth., D. laxiflorum sensu Miq., D. laxum var. kiusianum, D. laxum ssp. laxum, D. podocarpum auct. non DC. non Hook. & Arn., D. podocarpum DC. var. gardneri sensu Bedd., D. podocarpum DC. var. laxum)
 Hylodesmum leptopus (as D. gardneri Benth., D. laxum auct. non DC., D. laxum ssp. leptopus, D. leptopus, D. tashiroi)
 Hylodesmum podocarpum (as D. podocarpum DC., D. podocarpum DC. var. indicum, D. podocarpum DC. var. japonicum)
 Hylodesmum podocarpum ssp. oxyphyllum (as D. fallax var. mandshuricum, D. japonicum, D. mandshuricum, D. oxyphyllum DC., D. podocarpum DC. var. mandshuricum, D. podocarpum DC. ssp./var. oxyphyllum, D. podocarpum DC. var. polyphyllum, D. podocarpum DC. var. typicum, D. racemosum)
 Lespedeza thunbergii  (as D. formosum, D. thunbergii) 

 Lespedeza thunbergii var. thunbergii (as D. penduliflorum Oudem.)
 Maekawaea macrocarpa (as D. macrocarpum)
 Maekawaea rhytidophylla (as D. rhytidophyllum)
 Maekawaea tenax (as D. tenax)
 Ohwia caudata (as D. caudatum)
 Phyllodium pulchellum (as D. pulchellum)

References
  (2005): Genus Desmodium. Version 10.01, November 2005. Retrieved 2007-DEC-17.

External links 

 Trout, K. (2002). Trout’s Notes on the Genus Desmodium. Mydriatic Productions. Better Days Publishing.

 
Forages
Fabaceae genera