Opuntia fragilis (Nutt.) Haw.

Opuntia fragilis is a widespread, though inconspicuous, species; in many places, it flowers infrequently, if at all. Its easily detached stem segments are dispersed by animals and possibly water.

Shrubs, low, forming mats, 2-10 cm. Stem segments easily detached when terminal, dark green, subspheric to subcylindric, to flattened and elliptic obovate, (1.5-)2-5.5 × (1-)1.5-3 cm, low tuberculate (pronounced when dried), glabrous; areoles 3-5 per diagonal row across midstem segment, oval, 3 × 2.5 mm; wool white. Spines 3-8 per areole, in most areoles spreading, gray with brown tips, straight, ± acicular, terete, the longest 8-24 mm; depressed spines at base of areoles 0-3, 1-3 mm. Glochids in crescent at adaxial margin of areole, tan to brown, inconspicuous, to 3 mm. Flowers: inner tepals yellow, sometimes basally red, 20-26 mm; filaments white or red; anthers yellow; style white; stigma lobes green. Fruits tan, 10-30 × 8-15 mm, dry, glabrous; areoles 12-22, distal areoles bearing 1-6 short spines. Seeds tan to gray, flattened, warped, oblong to subcircular, 5-6 mm diam.; girdle protruding 1-1.5 mm. 2n = 66.

Alta., B.C., Man., Ont., Sask.; Ariz., Calif., Colo., Idaho, Ill., Iowa, Kans., Mich. , Minn., Mont., Nebr., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wis., Wyo.

Flowering summer (late Jun-early Jul).

Barren areas in grasslands, woodlands, sandy or gravelly soils, on outcrops of granite, limestone, or quartzite; 0-2400m.

Cactus fragilis Nuttall, Gen. N. Amer. Pl. 1: 296. 1818; Opuntia brachyarthra Engelmann & J. M. Bigelow; O. fragilis var. brachyarthra (Engelmann & J. M. Bigelow) J. M. Coulter