Plants 16-30-branched, forming clumps. Stems erect to ascending, cylindric or somewhat tapering distally, 20-30(-70) × (4-)6-9 cm; ribs 10-13, crests slightly undulate; areoles 15-25 mm apart. Spines 13-16 per areole, usually straight, divergent-porrect, pale translucent yellow; radial spines 8-12 per areole, 5-25 mm; central spines 4-6(-8) per areole, 30-72 mm, abaxial central spine usually descending, paler than other central spines, often fading whitish, somewhat flattened. Flowers 4-6 × 5-7 cm; flower tube 18-25 × 12-30 mm; flower tube hairs 1 mm; inner tepals usually pale pink with midstripes slightly darker, proximal ¹/3 greenish, 30-40 × 5-10 mm, tips relatively thin and delicate; anthers yellow; nectar chamber to 7 mm. Fruits green, becoming bronze where exposed to sun, 23-34 mm, pulp white. 2n = 22.

Flowering Mar-Apr; fruiting Jun. Arizona Upland Subdivision of Sonoran Desert, exposed slopes, bajadas, hills, mountains, desert scrub, igneous and sedimentary substrates; 300-900 m; Ariz.; Mexico (Sonora).

Although it was initially considered a variety of Echinocereus engelmannii, E. nicholii differs in chromosome number and a suite of morphologic characteristics. With its non-erumpent flower buds, diploid chromosome number, relatively small and usually pale flowers, green fruits, and exclusively yellow spines, E. nicholii more closely resembles E. ledingii than E. engelmannii.

FNA 2004, Benson 1969

Common Name: Nichol's hedgehog cactus Duration: Perennial General: Clump forming mounded cactus with 16-30 branches, the stems erect to ascending and cylindric to tapering above, 20-30 cm long by 6-9 cm wide, bearing 10-13 ribs with slightly undulate crests and areoles 15-25 mm apart. Spines: Usually 13-16 per areole and straight, pale translucent yellow with 8-12 radial spines per areole that are 5-25 mm long, usually 4-6 central spines per areole and these are 3-7 cm long, usually with a lower central spine that is descending and paler than the other spines, often fading white and somewhat flattened. Flowers: Pale pink 4-6 cm across by 5-7 cm tall, the floral tube about 2 cm across and 1-3 cm tall, the tips of the tepals are thin and delicate, the anthers yellow. Fruits: Green but becoming bronze in the sun, 2-3.5 cm long, the pulp white. Ecology: Found on rocky, sandy, or gravelly grounds of slopes or exposed sites in desert scrub, often on igneous or sedimentary substrates from 1,000-3,000 ft (305-914 m), flowers March-May. Distribution: Ranges across southern Arizona into northern Mexico. Notes: This species is similar to in appearance to both E. engelmannii and E. ledingii, pay attention to its having only yellow spines, the small and pale flowers, and green fruits. Ethnobotany: Unknown Etymology: Echinocereus is from the Greek echinos, hedgehog or spine and cereus, waxy, while nicholii is named for Andrew A. Nichol (1895-1961) an American biologist. Synonyms: Echinocereus engelmannii var. nicholii Editor: SBuckley, 2011