At least in the United States, Echinocereus pectinatus (diploid) has only pink or purple flowers, unlike the polymorphic species E. dasyacanthus (tetraploid). Echinocereus pectinatus differs from the entire E. reichenbachii species group in that the areoles of its relatively thick-walled flower tube have stouter spines and much shorter hairs. Superficially similar species west of the Continental Divide, formerly associated with E. pectinatus (E. pseudopectinatus, E. rigidissimus, and some Sonoran species), are more closely related to the E. reichenbachii species group with densely bristly flower buds and delicate, ephemeral inner tepals. Echinocereus pectinatus var. pectinatus is endemic to Mexico; reports from the United States were misidentifications of var. wenigeri,E. pseudopectinatus (in Arizona), and unusually short-spined plants of E. dasyacanthus.
Benson 1982, FNA 2003, Kearney and Peebles 1969
Common Name: rainbow cactus Duration: Perennial Protected Status: No status in Arizona. General: Stems solitary or with 2-3 basal branches and cylindroid, 10-30 cm long and 6-10 cm diameter, with 15-2 ribs bearing areoles that are elliptic to narrowly so, 4.5-6 mm and usually about 6 mm apart, the spines dense and obscuring the stem. Note that the stem has distinctive red and white banding. Spines: Spines appressed and dense obscuring the stem, pink to pale gray to straw colored and brown or white with 2-7 central spines per areole in 1-3 vertical series, these perpendicular to stem and straight with the longer 1-12 mm long, with 7-22 radial spines per areole and strongly comb-like to spreading but irregularly straight or curving downward in a low arc. Flowers: Flower 5-12.5 cm diameter and long with the areoles of floral tube bearing short hairs and stout spines, the inner tepals pink or purple only and oblanceolate with rounded apices, these 4.5-6 cm long and 12-15 mm broad, the filaments pink or yellow. Fruits: Fruit green to greenish-purple, with clusters of deciduous spines. Ecology: Not found in Arizona but present in New Mexico and Texas, east of the Continental Divide. Distribution: s AZ, s NM, s TX; south to c MEX. Notes: Similar to E. rigidissimus, distinguished by inner tepals E. reichenbachii species group (which includes E. rigidissimus among others) in that the areoles of E. pectinatus have relatively thick-walled flower tubes, stouter spines and much shorter hairs. Ethnobotany: No specific use of the species recorded, however the fruits of the genus were used as food. Etymology: Echinocereus is from the Greek echinos, hedgehog or spine and cereus, waxy, while pectinatus means comb-like. Synonyms: Echinocactus pectinatus Editor: LCrumbacher 2010, FSCoburn 2015