In most genera the only leaves have been modified into spines. Photosynthesis takes place in the stems. Cacti are associated with deserts, but they also occur in dry prairies, high mountains, pine forests, and in trees in the jungle. Cacti need bright light and well-drained soil to grow well. They also appreciate a cool, dry rest in Winter to encourage flowering.
Most species are at least moderately frost hardy if they are dry at the root.
Ferocactus wislizenii Trichocereus pachnoi Opuntia macrocentra Echeveria Family Crassulaceae. Most of the 150 or so species of echeveria occur in Mexico, but the genus ranges as far south as Peru. These are rosette succulents with red or orange flowers in spikes. They are very popular potted plants, but their use as landscape plants is somewhat limited, as most species dislike extreme cold and heat. In Northern California, where they are happiest, they are perhaps the favorite succulent plant group.