Apart from some opuntia, escobaria vivipara
(formerly classed as coryphantha vivipara) is the most widespread cactus in the US; the species has good frost tolerance and has adapted to a wide range of habitats, from Mexico all the way north to Canada, where it is one of only four cactus species in the country.
The plant is somewhat unremarkable; a globe or small cylinder, generally less than 2 inches in diameter but sometimes up to 8 inches, single or forming low clusters of 20 more stems, their surface covered by pronounced tubercles bearing 10 to 40 white radial spines and 3 to 12 central spines, darker in color, pointing outwards at various angles. Younger specimens have only the radial spines. The tubercles are marked with a groove along the upper surface, more evident in older plants - this is one feature that distinguishes the cactus from the similar pediocactus simpsonii
, as that has no grooves on the tubercles. The showy pink flowers make the cactus much more noticeable; they appear any time between spring and late summer, and are followed by green fruits.
As expected for a species with such a wide range, a number of regional variants have been proposed, mostly specific to the Southwest states, with different spine numbers and flower characteristics.