Plants unbranched or sometimes forming loose clumps of fewer than 20 somewhat flaccid branches. Stems erect or slightly decumbent, ovoid to cylindric with age, 7.5-17(-30) × (3.3-)3.8-7.5(-10) cm; ribs 8-11(-13), crests uninterrupted or undulate (sometimes depth of sinus between areoles is 90% of rib height in flowering plants with juvenile stem morphology); areoles (12-)15-17(-25) mm apart. Spines (2-)4-12(-16) per areole, straight or curved (radial spines sometimes sinuous); radial spines spreading, opaquely white, commonly with dark stripe on underside, often with contrasting black or brown spines in same areoles (rarely all brown or all white), aging gray; radial spines (2-)4-10(-12) per areole, (8-)11-39 mm; central spines (0-)1(-3) per areole, porrect or ascending, if curved, then usually directed upward, (10-)25-42(-62) mm, abaxial central spine like others in color or darker, flat to sharply angled. Flowers 5-11 × 5-11 cm; flower tube 10-15 × 10-30 mm; flower tube hairs 1-2 mm; inner tepals magenta [or nearly white], proximally sometimes darker or purplish maroon, 30-70 × (9.5-)12-15 mm, tips relatively thin and delicate; anthers yellow; nectar chamber (2-)3.5-6(-8) mm. Fruits bright red, dull carmine, or purplish maroon, less often orange-tan or purplish orange, 20-30(-50) mm, pulp magenta or red. 2n = 22.

Flowering Apr-Jun; fruiting Jun-Aug. Mesquite thickets, semidesert grasslands, interior chaparral, pinyon-juniper or pine-oak woodlands, limestone or igneous substrates, mostly south-facing hillsides; 900-2400 m; Ariz., Colo., N.Mex., Tex.; Mexico (Chihuahua, Sonora).

Frequently, some or all spines in each areole of Echinocereus fendleri are opaquely white, especially the lowermost (largest) radial spine, which is frequently strongly flattened (dorsiventrally compressed, its margins expanded and textured spongy or corky). On some immature plants, all the spines are modified in that way, reminiscent of spines of Pediocactus peeblesianus (Croizat) L. D. Benson.

Echinocereus fendleri has an indefinite number of (mostly) unnamed geographic races. One of these, var. rectispinus, of southeastern Arizona has enjoyed undeserved emphasis in the literature; it is often based on misidentifications of tetraploid E. fasciculatus.

The tuberculate stems and sparse, strangely modified spines of immature plants are retained to some extent in adulthood in some populations of Echinocereus fendleri var. fendleri. Such plants superficially resemble Pediocactus peeblesianaus. The name E. fendleri var. kuenzleri (Castetter, P. Pierce & K. H. Schwerin) L. D. Benson and its Mexican counterpart, E. hempelii Fobe, are based mainly on the stem feature. Immature plants of all populations share that distinctive appearance, strikingly different from immature plants of similar or related species, such as E. fasciculatus. In adulthood this convenient diagnostic characteristic is usually lost, rendering identification more difficult. On the Mexican border immature plants in some populations have as few as four spines per areole; they probably are intermediates with the obviously conspecific Chihuahuan taxon, E. hempelii Fobe.

Benson 1969, FNA 2003, Kearney and Peebles, 1979, Heil et al. 2013, Allred 2012

Common Name: pinkflower hedgehog cactus Duration: Perennial Protected Status: Salvage restriced status in Arizona. General: Hedgehog-like cactus consisting of up to 20 stems of varying heights forming loose clumps (usually 5 or fewer stems per clump), or stems solitary; stems erect to slightly decumbent and flabby, ovoid to cylindric, 7-25 cm tall and 4-8 cm diameter, with 8-11 ribs; ribs smooth or undulate, with areoles (axillary buds from which the spines emerge) 1- 2 cm apart along the ribs. Spines: Spines usually 4-12 per areole, straight or curved; central spines 1 or 2 per areole, or absent; the main central spine is up to 6 cm long, nearly terete (round in cross section), sticking straight out or curving upward, and usually dark colored; the second central spine, if present, usually much smaller and lighter in color; remaining spines are radial (emerging from the outside edge of the areole), these are spreading, usually 1-2 cm long, white with a dark stripe on underside, or with contrasting black or brown spines in same areoles (rarely all brown or all white), aging gray. Flowers: Flowers 5-11 cm long and about as wide; petals numerous, 3-7 cm long, magenta to dark purplish maroon, with thin, delicate tips; stamens numerous, topped with yellow anthers. Fruits: Fruit fleshy, 2-3 cm long, maturing bright red to dull carmine or purplish maroon, or even orangish; pulp magenta or red. Ecology: Found in sandy or gravelly soils in a wide variety of ecotypes on mostly south-facing hillsides from 3,000-8,000 ft (914-2438 m); flowers April-June; fruiting June-August. Distribution: CO and UT to TX and n MEX Notes: The systematics of this species (according to some) now include what were previously varieties of E. fasciculatus: var. fasciculatus and var. boyce-thompsonii. These are both rare cacti and are treated as separate species here E. fasciculatus var. fasciculatus has 5-20 stems, each 15-45 cm long, with 8-10 ribs and gray, deflexed spines emerging at right angles from the stem; E. boyce-thompsonii has 4-12 stems, each 10-20 cm long, with 14-18 ribs, a light colored principal stem and slightly longer than E. fasciculatus. Distinguish from E. coccineus by the flower color which is red to orange in that species (never purple-tinged!), while the flowers are pinkish-purple in this species; also the stems are tightly clustered into a mound in E. coccineus, while the stems are loosely clustered or occasionally solitary in this species. Sclerocactus parviflorus has a similar appearance and pink-purple flowers, but in that species the lower central spine is strongly hooked, the source of its common name, fish-hook cactus. Ethnobotany: The fruits were eaten raw or dried, and the stems were pit roasted and eaten. Etymology: Echinocereus is from echinos, spiny, and cereus, candle; fendleri is named for Augustus Fendler (1813-1883) a German botanical collector in North and Central America. Synonyms: None Editor: SBuckley 2010, AHazelton 2017