Acmispon helleri (Britton) A.A. Heller. Carolina Prairie-trefoil. Phen: (Jun-) Jul-Aug (-Sep). Hab: Dry woodlands and openings, originally probably limited to prairie-like sites (fire-maintained, post oak-blackjack oak savannas), generally on clayey soils, now primarily seen on roadbanks, along railroads, and in powerline rights-of-way, where mowing and bush-hogging have replaced fire as the force keeping the habitat open, sunny, and suitable for this plant of prairie affinities. Dist: A. helleri is endemic to the Piedmont of extreme sc. VA, NC, SC, and ne. GA.

Origin/Endemic status: Endemic

Taxonomy Comments: A. helleri is clearly closely related to A. americanus (= Lotus unifoliolatus, = Lotus purshianus, = Lotus americanus), of prairies of the midwestern states and various habitats farther west, which ranges east to LA, AR, MO, IL, IN, and WI. Isely (1981) reduced A. helleri to a variety (in Lotus), because it "is but one of many elements within the L. purshianus complex and its differences from the rest are less than among the California races," while also stating "since it has no breeding contact with var. purshianus, it is reasonably maintained as a species." Since A. helleri seems adequately separated from A. americanus by its narrower leaflets, glabrate vestiture, and allopatric distribution, we choose to reasonably maintain it as a species. See Sorrie (2015) for notes on its morphology.

Synonymy ⓘ: = S, Va; = Acmispon americanus (Nutt.) Rydb. var. helleri (Britton) Brouillet – FNA11.1, K3, K4; = Lotus helleri Britton – RAB, S13; = Lotus purshianus F.E. & E.G.Clem. var. helleri (Britton) Isely – C, SE3, Isely (1981), Isely (1998); = Lotus unifoliolatus (Hook.) Benth. var. helleri (Britton) Kartesz & Gandhi – K1; < Lotus americanus (Nutt.) Bisch. – F; < Lotus purshianus F.E. & E.G.Clem. – G

Links to other floras: = Acmispon americanus var. helleri - FNA11.1

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Heliophily ⓘ: 9