Desmodium tweedyi is an herbaceous flowering plant in the pea family native to northern Texas and southern Oklahoma popularly known as "Tweedy's ticktrefoil" or "tick-clover.

Along with other species in the Desmodium genus, D. tweedyi has become a candidate for soil enrichment, suppression of insect pests, mulch and green manure production, and making "good fodder for animals including bobwhite, turkey, grouse, deer, cattle and goats.

Desmodium is derived from the Greek word desmos which means "bond, fetter, or chain," referring to the connected segments of the fruit (legume) giving it a chain-like appearance.

The traditional taxonomy system sometimes referred to as "Linnaean classification" put each species in a hierarchy of formal ranks, each identified using binomial nomenclature – for example, the scientific name Desmodium tweedyi including the genus and epithet.

Botanist P. C. van Welzen offered the following advice:[5] I think, therefore, that the best solution is to choose the second option that Brummitt (1997) provides in his paper, namely, "retaining Linnaean classification, with paraphyletic taxa [including the common ancestor and some, but not all, of its descendants], but developing alongside it an independent clade-based dichotomous system with its own separate nomenclature.

As the third largest family of flowering plants -- with 730 genera and 19,500 species -- it is economically important with food sources for beans, peas, peanuts, and soybean.

The Christenhusz and Bing article inventorying the world's plants estimated that ca 2000 new species are described each year, with some concern that "the rate of discovery is slowing down, due to reduction in financial and scientific support for fundamental natural history studies.

The flower cluster's "inflorescence axis" occurs "with short hooked hairs, petals white with greenish or yellowish tinge, sometimes with lavender base.

Desmodium tweedyi grows in thickets in limestone areas in central Texas from "Blackland Prairie west to Rolling Plains and Edwards Plateau.

This plant species is found in north-central Texas with a total range extent of from 8,000 up to one million square miles, and thus endemic or limited to one State within one nation, a very small area in terms of the global scale.

[15] However, 25 of the 66 specimens of Desmodium tweedyi held in American herbaria for the period of years from 1872 to 2015 were collected in Oklahoma, confirming this State as part of this species' geographical range.

Desmodium tweedyi is one of 99 specimens Tweedy collected in Texas, listed by botanist Nathaniel Lord Britton in an 1890 journal article of the New York Academy of Sciences.

Clearly Tweedy sent this specimen to Britton for identification, and this NYBG botanist made the determination that it was a new species in the Desmodium genus, naming it in honor of its first collector.

[16] These notes reveal an interesting journey for this Tweedy discovery from Texas to Britton in NYC, to a botanist at Harvard University, and then to the New York Botanical Garden -- where the Steere Herbarium holds this find with the second largest collection of plants in the world, 7.8 million specimens!

A 1977 Masters research project done by a Texas resident, John Williams, titled "Biosystematic Study of a Desmodium Complex," aimed to sort out the interrelationships between the three species that have been commonly confused in the past -- D. canescens, D. tweedyi, and D illinoense.

Anna Murray Vail (1883-1955) published an article in the Torrey Botanical Club's Bulletin in 1892 in which she noted marked similarities of the leaves, flowers, and fruit legumes in three genera, all members of the Fabaceae plant family -- Hedysarum, Meibomia, and Desmodium.

In a 2004 study, D. tweedyi was evaluated with 14 other legume species for improving soil fertility, nitrogen fixation, and usage in "woodland restoration, deer plots, goat browse and cattle pastures" for Texas' central Cross Timbers region.

"[22] A 2008 study in Agronomy Journal evaluated D. tweedyi with two other Texas legumes for use in the southern US "for pastures, biomass production, wildlife plantings, rangeland reseeding, or native prairie restoration.

"[23] D. tweedyi was found to contain high concentrations of nitrogen compared to other perennial legumes "and should improve the overall nutritive value of unfertilized grass stands used for ruminant production.

[14] It received a global status of G3 or "Vulnerable" in 2001 because this species is "at moderate risk of extinction or collapse due to a fairly restricted range, relatively few populations or occurrences, recent and widespread declines, threats, or other factors."

[14] As an endemic in Texas and Oklahoma, Desmodium tweedyi is very limited in its distribution, and would benefit from conservation efforts and agricultural applications in a wider geographical range.