by Richard Pearman

Created on: February 03, 2009

This contains a lot of Latin names of plants and scientific terms for groups of plants. You can use a search engine to look these up.

Let's start by getting a few things straight. Not all cacti grow in deserts. Many grow in semi-deserts, mountains, beaches or even rain forests. Not all cacti, even desert ones, have fleshy stems, lack leaves or have spines. Not all desert plants that are fleshy and/or spiny and/or leafless are cacti. Agaves (century plants), Aloes (including Aloe vera), Euphorbias (includes the pencil cactus and the baseball cactus), stapeliads (carrion flowers), Lithops (living stone plants), Pachypodiums, Crassulas (Jade plants), Araucaria (monkey puzzle trees), cycads, Welwitchias, palms etc. are not cacti! Perhaps you should note that Schlumbergera (Christmas cactus), which isn't very fleshy, grows in rain forests and doesn't have spines or leaves (but the stems look like leaves), is a real cactus. Euphorbia obesa (baseball cactus), which does grow in a desert, has a very fleshy stem, has nothing that looks like leaves but doesn't have spines, is not a cactus.

Perhaps I should also mention that all cacti are native to the Americas although one of the forest ones seems to have got to Africa and Asia without human assistance.

The desert, semi-desert, mountain and beach cacti have similar adaptations and can be cultivated in more-or-less the same way (also some of them grow in more than one of these habitats). The rain forest cacti are rather different. I will talk mostly about the former group.

One way to reduce water loss is to have a thick, waxy skin. All cacti have this one pretty much covered.

Another way is to reduce or get rid of leaves. The four sub-families of cacti have somewhat different leaves. The Pereskoideae (which doesn't include any common cacti) have large, non-fleshy leaves but they don't grow in deserts (so I'm not going to talk about them here). The Maihuenioideae (which only has two rare species) have cylindrical, fleshy leaves. The Opuntioideae (includes prickly pears and chollas) are rather varied: Pereskiopsis and Quiabentia have flat, slightly fleshy leaves, Austrocylindropuntia and Cylindropuntia have fleshy, cylindrical leaves, the others have small, short-lived, scale-like leaves. The Cactoideae (which includes most cacti except prickly pears and chollas) don't have leaves.

If you're going to get rid of your leaves, how do you photosynthesize? Almost all cacti have stems that photosynthesize (and are therefore green or

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