Echinocereus rigidissimus var. rubrispinus, known as Ruby Rainbow Hedgehog, is a beautiful cactus with red-pink, very dense spines arranged in such a way that they are harmless. Its magenta flowers are quite large and appear in late spring. As the blooms fall off, small whitish scars remain. This columnar cactus stays small, usually growing not more than nine inches tall.
This cactus, called a calcifuge because it does not like alkaline soil, originated in Arizona, New Mexico and Northern Mexico. I find the fact that this cactus is a calcifuge odd, as the soil in Arizona is quite alkaline. I don’t normally water this cactus as it only requires rainwater, but I do occasionally water it in the summer with water that has a tad of vinegar added to counter the alkaline soil. I do not water it at all in winter, as it is rot-prone. It seems to be growing just fine.
Most people are more familiar with the Arizona Rainbow Hedgehog (Echinocereus rigidissimus) which has bands of grey and red spines at irregular intervals. It is also attractive, and has the same gorgeous flowers. Usually the Arizona Rainbow's red color deepens in full sun, causing the alternating color variation to stand out even more.