All cacti are succulents. However, not all succulents are cacti. Actually, cacti are a very unique family. Their distinctive spines and thorns are very specialized leaves and stems. Such specialized leaves can not photosynthesize without green chlorophyll. Therefore, cacti rely on their succulent green trunks for photosynthesis. Their trunks work as foliage.

But of course, not all succulents are cacti. Other succulents have succulent leaves. Most also have succulent stems. Some, such as most agaves and some aloes, are spiny, but not like cacti are. They have real leaves that happen to be spiny. Yucca are supposedly succulent, likely because of their relation to agave. However, they lack succulent parts.

Furthermore, not all succulents are drought tolerant. Many are so only because they are naturally native to desert or chaparral climates. Many others are naturally native to less arid climates. Some that are native to tropical rainforests, like epiphyllum, crave regular watering. Many succulents thrive in harsh exposure. Some prefer a bit of cooling shade.

Succulents are generally very adaptable to container gardening. Ironically though, a few of the most familiar sorts are not as complaisant to containment. Several cacti and other desert species need more water while confined. They must compensate for their inability to disperse roots. However, frequent watering or even excessive rain might promote rot.

Agaves, including those of desert climates, happen to perform splendidly within big pots. In fact, some perform too splendidly. If they grow too big and heavy to move, they are as permanent as if in the ground. Their dangerously spiny foliage compounds the problem. Overgrown cacti are both very difficult to move, and likely to break apart in the process.

Fortunately, there are plenty of smaller, tamer and thornless succulents to choose from. They contribute a remarkable range of foliar form, texture and color to the garden. Some contribute colorful bloom. A few, such as aloes and agaves, produce sculptural bloom. Most succulents are naturally resistant to pathogens, and easy to propagate vegetatively. Rooted scraps are less expensive than nursery stock is.