Thornber's Fishhook Cactus

The epithet fasciculata was long misapplied to Mammillaria thornberi; it correctly pertains to Echinocereus fasciculatus (Engelmann) L. D. Benson.

Mammillaria thornberi is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Plants branching prolifically from base, every branch with independent root system, connections to rest of clone ephemeral, resulting in dense clumps of independently rooted stems. Roots diffuse, upper portion not enlarged. Stems slender cylindric, 4.5-10(-30) × 2-3.5 cm, tapered at base, firm; tubercles 5-9 × 5-9 mm; axils appearing naked; cortex and pith not mucilaginous; latex absent. Spines 14-22(-23) per areole, whitish to yellowish near base, pale reddish brown to nearly black toward tips, glabrous; radial spines 13-21 per areole, whitish, with reduced dark tips relative to central spines, bristlelike, 5-9 × 0.16 mm, stiff; central spines 1(-3) per areole, porrect, hooked, (7-)9-18 × 0.16-0.45 mm; subcentral spines 0(-3) per areole, adaxial to central spines, ± transitional to radial spines. Flowers 1.5-3 × 1.2-2.5 cm; outermost tepal margins densely short fringed; inner tepals white or pinkish with bright rose-pink midstripes, 14-19 × 5-7 mm; stigma lobes magenta, 3-6 mm. Fruits bright red, obovoid to nearly clavate, 7-15 × 4-7 mm, juicy only in fruit walls; floral remnant persistent. Seeds black, 0.9-1.1 × 0.8-1.1 × 0.7 mm, pitted; testa hard , brittle; anticlinal cell walls straight (not undulate); interstices conspicuously wider than pit diameters; pits bowl-shaped. 2n = 22.

Ariz.; Mexico (Sonora).

Flowering Apr-May, Jul-Aug; fruiting Oct-Nov, Feb-Mar.

Sonoran desert scrub, valley floors, under shrubs, silty or sandy soils; 400-600m.

Cochemiea thornberi is a species of cactus known by the common names Thornber's fishhook cactus and Thornber's nipple cactus. It is native to Arizona in the United States and Sonora in Mexico.

This plant has numerous branches that all root in the ground, forming a clump of rooted stems all belonging to one plant. The stems are cylindrical and usually measure up to 10 centimeters tall, but known to reach 30. They are up to 3.5 centimeters wide. There are up to 21 bristle-like radial spines on each areole and one to three hooked central spines. The flower is up to 3 centimeters wide and has white or pink inner tepals with pink midstripes. The flowers bloom most often after heavy rainfall. The fruit is bright red and up to 1.5 centimeters long. It is edible. It contains black seeds.

This plant is associated with nurse plants. It often grows beneath the branches of Ambrosia dumosa. The habitat is desert scrub. There are two main population areas in Arizona, one in the Avra Valley and Saguaro National Park and one on the Tohono O'odham Indian Reservation. This species was abundant in the Avra Valley up until the 1930s until a freeze which decimated the population. There are now a total of about 600 plants in all the populations together.