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Coryphantha vivipara (Nutt.) Britt. & Rose

Cushion cactus; Spinystar

Cactaceae (Cactus family)

Synonyms: Escobaria vivipara (Nutt.) Buxbaum; Escobaria vivipara (Nutt.) Buxbaum var. vivipara; Mammillaria vivipara (Nutt.) Haw.

General Description: A low-growing cactus, 3-10 cm tall and about equally wide, with one to several stems that are more or less round to short-cylindric in outline and have a top-shaped base. Tubercles are spirally arranged, 5-15 mm long, and distinctly grooved on the upper side. Areoles (special cushions bearing the spines) have 3-5 main spines about 10 mm long, and 10-20 smaller, slender marginal spines. Flowers are showy, bright reddish-purple, and about 3-4 cm wide and long. Fruits are greenish, oblong, 1-2 cm long, and have brown seeds.

Illustration.

Field Identification Tips: Cushion cactus is more or less round in outline except for the top-shape base. The tubercles are not arranged on ribs, as the stem is ribless. The showy flowers make plants conspicuous for awhile, but then the plants dry and shrink downward into the substrate and are difficult to observe when dormant.

Phenology: Flowers May and June.

Similar Species: Coryphantha missouriensis (nipple cactus) is separated by its greenish-white or yellowish flowers, globular, reddish fruits, black seeds, and shorter tubercles about 6-9 mm long. Two other genera of cactus occur in Idaho. Opuntia species (prickly pear cactus) are readily distinguished by their jointed and flattened stems. Species of Pediocactus (hedgehog cactus) have longitudinally ribbed stems. Idaho material has whitish to pinkish flowers about 2 cm long.

Habitat: Dry valleys and plains. Open, gentle to steep, rocky slopes and flats with sagebrush or conifer species in Idaho.

Global Distribution: Alberta south to Arizona, east to Minnesota, and Texas, as far west as southeastern Oregon.

Idaho Distribution: Lemhi County, and also reported for Owyhee County.

References:

Benson, L. 1982. The cacti of the United States and Canada. Stanford University Press, Stanford, CA.

Welsh, S. L., N. D. Atwood, L. C. Higgins, and S. Goodrich. 1987. A Utah flora. Great Basin Naturalist Memoir No. 9. Brigham Young University, Provo, UT. 894 pp.