Many years ago I developed a fascination with cold-hardy cacti. There are several Opuntia spp. (Prickly Pears) that naturally occur in the Midwest and one in the Northeastern U.S. (Opuntia humifusa).
Spinystar (Coryphantha vivipara) is quite different and only occurs as far east as Minnesota. It has bright magenta flowers and a single, cylindric stem. This species can be grown in the Northeast but may develop rot near the base if it is allowed to get too wet, particularly during cold weather. This is probably what naturally limits its range to the west.
