Cacti are simply a family, or subcategory of succulents. Cacti are found as native plants only in the Western Hemisphere. Occurring throughout North and South America, the greatest concentration of species is found in Mexico northward into Arizona, New Mexico, and West Texas. Many species have especially showy flowers and are excellent companion plants for many smaller growing xeric native perennials and ornamental grasses.
The largest genus of cold hardy cacti is Echinocereus, commonly known as Hedgehog Cactus due to its decorative spines. This is one of my favorite genera because of the vast number of subspecies and variants that can be found. In fact, there are many collectors who concentrate solely on this huge group. Important ornamental species in the genus include E. triglochidiatus, E. verififlorus, E. reichenbachi, and E. fendleri. However, there are many other species in the genus that have cold hardy members as well.