Green-flower Hedgehog Cactus

This cactus has a small spherical to ovoid, sometimes elongated or cylindrical in shape, stem 3 cm (1.2 in) to over 30 cm (12 in) tall and up to 1 to 9 cm (0.39 to 3.54 in) wide. The 6 to 18 ribs are clearly humps. It is mostly unbranched but it may occur in squat clusters of several branches. The body of the plant is ridged and lined with many areoles bearing spines. The spines may be red, yellow, white, purplish, or bicolored, sometimes with darker tips and are up to 2.5 cm (0.98 in) long. The 8 to 24 marginal spines are also red, cream or brown and up to 1.8 cm (0.71 in) long. The flower is up to 3 cm (1.2 in) long and has tepals in shades of yellowish, brownish, greenish, or occasionally red, with darker reddish midstripes. The tepals are thin at the tips. They are usually wide open, funnel-shaped and green to yellow-green. They are 2.5 to 3.0 cm (0.98 to 1.18 in) long and large in diameter. The fruits are spherical, green and heavily thorny.

Echinocereus viridiflorus is widespread in the US states of South Dakota, Wyoming, Colorado, Kansas, New Mexico, Oklahoma and Texas, as well as in the neighboring Mexican states of Coahuila and Chihuahua. It has yellow-green flowers. This rare variety is endemic to Brewster County, Texas, where it grows in beds of Selaginella in rocky soils of novaculite origin. There was only one population known as of 1984, and it probably will not expand its range because it is limited to a specific mineral substrate.