Wednesday, January 13, 2010

What makes a cactus a cactus?

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Some people think that any spiney plant is a cactus. Real cactus in the Cactaceae family are only found in North and South America. There is one lone native species of cactus in Africa the Rhipsalis baccifera, but it is assumed that it is a transplant. All of the cactus in the Middle East and elsewhere are non-native species. The plant above looks rather spiney. Is it a cactus?

Look closely at the base of the spines near the green skin. This fuzzy white area is the areole. In some species of cactus the areoles have developed into small, detachable stickers called glochids that are very sharp and painful to the skin. No areoles, no cactus, simple.

Although this cactus looks fierce, it is rather easy to avoid since it is a variety of Carnegiea gigantea, aka saguaro. Although saguaro cactus have become synonymous with desert, they are actually only found in the Sonoran Desert of Arizona and Mexico and in an extremely small part of California.

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