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Desmodium is a genus in the flowering plant 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.
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.
Several Desmodium species contain potent secondary metabolites that are released into the soil and aerially. These compounds are used aggressively in agriculture in push-pull technology to manage two major pests of cereals, especially maize and sorghum. High amounts of antixenotic allomones - chemicals produced by Tick-trefoils, for example, repel insect pests - and the allelopathic compounds kill weeds in push-pull farming. D. intortum and D. uncinatum are inter-cropped in maize and sorghum fields to repel Chilo partellus, a stem-boring grass moth and suppress witchweeds including Asiatic witchweed (Striga asiatica) and purple witchweed (S. hermonthica).. Different Desmodium species produce different profiles of organic compounds through their root systems. Reasons for 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.
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.
The caterpillars of the lesser grass blue (Zizina otis) and the two-barred flasher (Astraptes fulgerator) feed on tick-trefoils. Deer also appear to rely on some species in certain areas, particularly during the more stressful summer months.
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.
- Desmodium acanthocladum F.Muell.
- Desmodium adscendens DC. - Strongback
- Desmodium canadense – showy tick-trefoil, Canadian tick-trefoil
- Desmodium canescens – hoary tick-trefoil
- Desmodium ciliare (Muhl.) DC. – hairy small-leaved tick-trefoil
- Desmodium concinnum DC.
- Desmodium concinnum var. concinnum (syn. D. penduliflorum Benth.)
- Desmodium cuspidatum (Muhl.) Loudon – toothed tick-trefoil, large-bracted tick-trefoil
- Desmodium dillenii Darl. (sometimes considered a variety of D. paniculatum)
- Desmodium discolor Vog.
- Desmodium elegans DC.
- Desmodium gangeticum
- Desmodium glabellum
- Desmodium glabrum (Mill.) DC. (syn. D. molle (Vahl) DC.)
- Desmodium glutinosum (Willd.) Alph. Wood – pointed-leaved tick-trefoil, large tick-trefoil
- Desmodium heterocarpon (L.) DC.
- Desmodium hookerianum D. Dietr. (syn. D. podocarpum Hook. & Arn.)
- Desmodium humifusum (Muhl. ex Bigelow) Beck
- Desmodium illinoense – Illinois tick-trefoil
- Desmodium incanum – creeping beggarweed, Spanish clover, Spanish tick-trefoil, Kaimi clover, kaʻimi (Hawaiʻi)
- Desmodium intortum – greenleaf desmodium
- Desmodium khasianum (syn. D. oxyphyllum auct. non DC.)
- Desmodium laxiflorum DC. (syn. D. incanum sensu auct.)
- Desmodium lineatum (Michx.) DC. – linear-leaved tick-trefoil
- Desmodium marilandicum (L.) DC. – smooth small-leaved tick-trefoil
- Desmodium molliculum (Kunth) DC. – Burbur
- Desmodium nemorosum F.Muell. ex Benth.
- Desmodium neomexicanum (syn. D. bigelovii, D. humile, D. lilloanum, D. parvum, D. spirale auct. non DC. non Griseb. non (Sw.) DC., D. spirale (Sw.) DC. var. bigelovii)
- Desmodium nudiflorum (L.) DC. – bare-stemmed tick-trefoil, naked-flowered tick-trefoil
- Desmodium oojeinense
- Desmodium ospriostreblum (syn. D. spirale DC., D. tortuosum sensu Hepper)
- Desmodium paniculatum (L.) DC. – panicled tick-trefoil
- Desmodium perplexum – perplexed tick-trefoil
- Desmodium procumbens (syn. D. spirale (Sw.) DC., D. sylvaticum, D. tenuiculum)
- Desmodium psilocarpum
- Desmodium ramosissimum G.Don.
- Desmodium rhytidophyllum F.Muell. ex Benth.
- Desmodium rigidum (Ell.) DC. – rigid tick-trefoil
- Desmodium rotundifolium (Michx.) DC. – prostrate tick-trefoil, round-leaved tick-trefoil, dollar leaf
- Desmodium spirale Griseb. (disputed)
- Desmodium tortuosum (Sw.) DC.
- Desmodium triflorum
- Desmodium tweedyi Britton – Tweedy's tick-trefoil
- Desmodium uncinatum – silver-leaved tick-trefoil, silverleaf
- Desmodium varians (Labill.) G.Don
- Codariocalyx motorius – telegraph plant (as D. gyrans, D. motorium, D. roylei)
- 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.)
- Ohwia caudata (as D. caudatum)
- Phyllodium pulchellum (as D. pulchellum)
- Dendrolobium umbellatum (as D. umbellatum (L.) Benth.
- Dendrolobium triangulare (as D. Desmodium umbellatum Moritz.
- International Legume Database & Information Service (ILDIS) (2005): Genus Desmodium. Version 10.01, November 2005. Retrieved 2007-DEC-17.
- "The Plant Encyclopedia - Desmodium". The Plant Encyclopedia. Retrieved 17 January 2014.
- "Plants Profile for Desmodium (ticktrefoil)". plants.usda.gov.
- "Know Your Deer Plants: Beggar's Lice - Quality Deer Management Association". 25 January 2012.
- ILDIS (2005)
- Pires Lima LC, de Queiroz LP, de Azevedo Tozzi AMG, Lewis GP (2014). "A Taxonomic Revision of Desmodium (Leguminosae, Papilionoideae) in Brazil". Phytotaxa. 169 (1): 1–119. doi:10.11646/phytotaxa.169.1.1.
- See discussion at Desmodium incanum
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- Trout, K. (2002). Trout’s Notes on the Genus Desmodium. Mydriatic Productions. Better Days Publishing.