Cactus gardens can be easy to grow and surprisingly thrive in many climates. There are two main types of cacti, sun (desert) and shade (tropical), the former being more commonly grown. Within each group, there are yet many more different types of cacti and just as many more ways to use them in your garden.
Native to the Americas, sun cacti are often found in desert-like conditions. They require a great deal of sun and are very hardy, being able to survive temperature extremes and lack of water by going dormant. Given a choice, these cacti prefer a rich, well draining soil. Make sure the soil dries out between waterings, because the worst thing you can do to a cactus is leave its roots sitting in water.
Some different types of sun cacti are prickly pear, barrel, and pincushion. Prickly pear cacti are rather common in regions of the Southwest and are delightful because they produce an edible fruit. Barrel cacti are spine-covered columnar cactus that can grow to be quite tall. Pincushion cacti, on the other hand, are often much shorter, sometimes even being rather small. While you can plant a garden containing all of one kind, it would be much more interesting to plant multiple varieties. For instance, you could plant a tall barrel cactus with small pincushion cacti in front. Make sure tall plants do not put shade over smaller ones.
Shade cacti are somewhat less common, due to the fact that they need a more tropical climate. You can have this sort of garden in a cooler climate, however, by keeping them in pots and moving them indoors during colder weather. Tropical cacti need more fertilizer, more water, and less sun than desert cactus.
Whatever type of cactus you choose, do a little research and make sure it is able to grow in your region. Plant different types of cactus together that have similar growing needs, such as light, soil, and water requirements.