Subspecies, varieties, forms and cultivars of plants belonging to the Echinocereus viridiflorus/russanthus complex
Echinocereus carmenensisW.Blum, Mich.Lange & E.Scherer in W.Blum et al.: has stocky body covered by tight yellowish pectinate spines and peculiar chocolate-scented flowers. Distribution: La Cuesta, passo Sierra del Carmem, Coahuila, Mexico.
Echinocereus milleriW.Blum, Kuenzler & Oldach: has the "hairy" seedlings of Echinocereus viridiflorus var. neocapillus, but has fewer spines it is also similar to the yellow spined Echinocereus viridiflorus subs. Correllii (which it obviously is not).
Echinocereus russanthusD.Weniger: has spheric to cylindrical stems, 8-30 tall and 4-8 cm Ø; ribs 10-20. Spines: Interlocking, bristly, typically reddish to brown, radiating in all directions. Distribution: Chihuahua (Mexico) and N-W Texas (USA).
Echinocereus viridiflorusEngelm. in Wisliz.:ssp. viridiflorus(Typical form) With small stems and relatively pure yellow flowers, extends from central New Mexico and the Texas Panhandle to South Dakota.
Echinocereus viridiflorus var. canusA.M.Powell & Weedin: has hairy juvenile forms. Distribution: Solitario, Sandstone ridge above Righthand Shutup, Presidio Co., Texas, USA.
Echinocereus viridiflorus subs. chloranthus(Engelm.) N.P.Taylor: has 10-18 ribs, 5 or more central spines, giving the plants a bristly appearance, it is often considered a separate species (Echinocereus chloranthus). Distribution: W. Texas, S.E. New Mexico, and N. Mexico.
Echinocereus viridiflorus subs. cylindricus(Engelm.) N.P.Taylor: The common morphotype grows at middle altitudes in Texas and southeastern New Mexico, it has 0-2(-3) central spines.
Echinocereus viridiflorus subs. davisii(Houghton) N.P.Taylor: In the broad senseEchinocereus viridiflorusmay prove paraphyletic with respect toEchinocereus davisii, but they are phenologically isolated, withEchinocereus davisiiflowering earlier and thus appearing reproductively isolated in the wild.
Echinocereus viridiflorus subs. davisii cv. brevispinushort.: has very short spines, usually radial, pectinated, stout, fang like, white whit a dark contrasting tip 2-4 mm long. Spine clusters looks like small starfishes.
Echinocereus viridiflorus var. montanushort.: has significantly depressed stems solitary or in low clusters (mostly less than 2 cm tall). Distribution: Southwestern USA (Monarch Pass, Colorado?)
Echinocereus viridiflorus var. robustiorKuenzler: It is a more robust form but not sufficiently differentiated and considered merely a local variant ofEchinocereus viridiflorus var viridiflorus. Distribution New Mexico.