Liatris mucronata de Candolle var. interrupta Gaiser

Corms elongate or becoming rhizomes. Leaves 50–120 × 2–7 mm. Heads in loose, spiciform arrays (widely spaced, stems evident). Involucres 10–15 mm. Phyllaries in 3–5 series. Florets 4–6. 2n = 20, 40.

Flowering Aug–Oct(–Nov). Gravelly and rocky slopes, canyon bottoms, grassy areas, mesquite, commonly over limestone; 10–1800 m; La., N.Mex., Tex.; Mexico (Chihuahua, Coahuila, Nuevo León, San Luis Potosí, Tamaulipas).

In the southern third of Texas, and in adjacent Louisiana, New Mexico, and Mexico, heads of Liatris punctata tend to be more widely spaced than characteristic for the species over the rest of its range. The most distinctive plants are in trans-Pecos Texas (and Mexico), and they occur at higher elevations than those in the more eastern range. Corms usually are elongate or rhizomiform; Gaiser described L. mucronata var. interrupta from a variant with subglobose corms. Intergrades in head congestion also are encountered, even northward into the Texas panhandle, and the variety is not sharply delimited. The populations with widely separated heads probably were ancestral to L. bracteata and L. cymosa, as well as a race (yet unnamed) with piloso-hirsutulous leaves, which occurs on the Edwards Plateau.