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Cacti & Succulents

By Denise Levine, U. C. Master Gardener

Do you know the difference between a cactus and a succulent?

All cacti are succulents, but not all succulents are cacti. Succulents (from the Latin word “succulentus,” for juice or sap) are defined by their moisture-storing capacity and come from many botanical families. Medicinal aloe veras and familiar Chicks and Hens are two examples of succulents many of us are familiar with.

Cacti have small, round, cushion-like structures called areoles from which spines, branches, hair, leaves and even flowers grow. While many succulents may look like cacti in every other respect, if they don’t have these circular areoles, they are not in the cactus (Cactaceae) family.

Another distinction is that succulents are native to most parts of the world, but cacti are only indigenous from Alaska to Chile in the Western Hemisphere. Vermont, New Hampshire and Maine have never found a native cactus, but Canada has found several that have evolved to survive Canada’s freezing winters.

Cactus varieties and other succulents are known as survivors. Their tough skin makes them unappetizing to most pests and predators, and because their stems, leaves or roots hold so much water, they are able to survive long dry spells.

Thorny spines are the best defenses for many varieties of cactus. But other succulents have even more creative tricks for survival.

Fenestraria rhopalophylla
Fenestraria rhopalophylla
You can see one survival technique in Baby Toes, an especially easy succulent to find and grow. Its common name comes from its appearance, jade-green clusters of what look like smooth infant toes. But its botanical name, Fenestraria rhopalophylla, hints at its special talent. Often partially buried, this plant has translucent, window-like tips on top to admit light.

Haworthia maughanii is another survivor. A black-green succulent that looks like little angular rocks protruding from the earth, this plant also burrows in rocky soil for insulation against the heat. It photosynthesizes from its “solar cells.”

Anacampseros papyracea, a light green plant that looks like a handful of snakes, takes this solar technology a step farther. In keeping with its snakelike appearance, this plant has scale-like leaves that prevent sunburn, conserve moisture, admit light and keep out excess heat.

The incredible variety of whimsical and fantastic succulents and cactus makes choosing one, or even five, exquisite torture.

But whether you decide to adopt a giant spined suaro cactus which can grow 50 feet tall (after 250 years) or a tiny rosette that would fit in a thimble, the way succulents and cactus are potted can mean the difference between failure and success.

Some experts say the best pot for a cactus or other succulent is a clay pot with a large drainage hole. Choose a pot that is half as wide as the height of the plant, and whether it is new or old, scrub it well with soap and hot water. Cover the drainage hole with shards of broken pots.

Buy a potting mix specifically for succulents or mix your own with equal parts of commercial potting soil and coarse builder’s sand. If you mix your own soil, pasteurize it by heating it in your oven at 250ºF degrees for at least 30 minutes.

Because cacti and succulents usually grow very slowly, planting a small-scale desert scene for a sunny window can be a striking way to enjoy several compatible plants. A 13-inch dish garden could hold up to a dozen different cacti placed around thoughtfully chosen rocks and conjure up images of real “cactus country.”

Do not water a newly repotted cactus or succulent immediately. Give it at least a week before you water unless you are repotting a very young plant. Then dampen the soil, but do not soak.

The key to watering cacti is restraint. Remember that some cacti are already 95 per cent water. The best way to tell if cacti and other succulents are getting enough water is to look closely at them. They should be plump and well filled with water. If they seem slightly puckered, wet them more thoroughly each time, but always remove any standing water that drains through.

Please join Master Gardeners at Connolly Ranch on Thursday, September 22, from 9 a.m. to noon, for a morning of garden tours and answers to fall gardening questions. Connolly Ranch is located at 3141 Browns Valley Road in Napa.

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