Echinocereus acifer

The plant sprouts from the base, forming small cushions of 5 to 8 stems. The dark green, cylindrical plant body grows to a height of 10 to 40 cm (3.9 to 15.7 in) and a diameter of 5 to 10 cm (2.0 to 3.9 in). It has 9 to 12 heavily warty, tuberous ribs. The tomentose areoles on new shoots are 1 to 1.5 cm (0.39 to 0.59 in) apart and about 3 mm (0.12 in) in diameter. The thorns are yellow to reddish-brown, later turning gray, with up to 5 central spines surrounded by 10 to 15 radiating marginal spines. Buds emerge from a woolly white pad with reddish-brown bristles. The funnel-shaped flowers are red on the outside and yellow on the inside, rarely crooked, and measure 8 to 12 cm (3.1 to 4.7 in) long with a diameter of up to 10 cm (3.9 in). Unlike the monoecious flowers of Echinocereus polyacanthus, the flowers of Echinocereus acifer are hermaphroditic and self-pollinating. The stamens are yellow, and the stigma is green to light green. The oval fruits remain greenish, measuring 2 cm (0.79 in) in diameter and 3 cm (1.2 in) in length.

Echinocereus acifer is found in the Mexican states of Guanajuato, Zacatecas, San Luis Potosí, and Durango, typically growing in rocky forest areas, moss, or rock crevices.