Cacti can be relatively pricey — especially if you want some specially bred variety -- but compared to orchids, for example, they're cheap. The most you might pay in San Diego for a rarer cactus would be about $80.
At swap meets and most nurseries, vendors have what many expert collectors call "introductory cacti"; that is, cactus varieties that are common and easy to grow.
Most of the introductory public just wants to see flowers, but serious collectors don't care about flowers. They care about the species and the form of the plant and staging it in a wonderful pot. It becomes more like a sculpture. One collector I talked to told me that he'd seen grocery stores go so far as to glue flowers on the top of cacti -- flowers that don't belong to the cacti, of course -- but they glue them there so that the cacti will sell. That's just bizarre.
And speaking of bizarre, here's an interesting coincidence; call it an evolutionary mystery. The forms of many underwater plants and animals are eerily similar to the forms of cactuses. The tuna fish and the fruit of the prickly pear cactus, the "tuna fruit," look more than a little alike. Anyone who's ever seen a sea urchin knows that they would seem right at home on a sand dune. In fact, the rolling sandy bottom of the ocean even looks a little like the desert. So what gives? The wettest and the driest ecosystems on our planet have developed almost identical shapes and forms. Weird. (Cue the music from The Twilight Zone...doo-di-doo-doo, doo-di-doo-doo....)
At one point, Knapik gently took issue with the name of the cactus club. He said, "Back when I was president, I asked them if we could change it, and they said no, it would be too hard to change the paperwork. But it should be 'The Cactus and OTHER Succulents Society.' Because cacti are succulents."
Cacti are succulents because they remain succulent (moist) in the most arid conditions. Many varieties of cactus are edible, and some would even pun that they are succulent in salads. In the plant world, succulents store water in their stems, leaves, or roots. It wouldn't be too much of a reach to call cacti (and other succulents) the camels of the plant world.
The spines on a cactus are a modified form of leaf. The spines are designed to protect the cactus's new growth from the pounding desert sunlight and to regulate water loss (more on this point later). The spines also often keep the cacti from being eaten by desert animals such as the bighorn sheep. Many cactus spines are more like hairs than thorns, and in some cactuses these hairs grow coarser and coarser until you'd rather pet a porcupine than toss a cactus-football. In fact, the cactus is like the porcupine of the plant world.
Neither the spines nor the succulence of cacti is a defining characteristic. But the areole is. The areole in a cactus is a highly specialized, cushionlike tissue structure out of which the spines and flowers grow. No other plant in the world has one. Toughened, hardened, and drought tolerant, all cacti are succulents, but not all succulents are cacti. Which is to say that cacti store water, but other water-storing plants don't have an areole that grows spines.
Cacti take the thorny crown as the most popular of the succulents. People champion cacti for their brilliant flowers, unusual shapes, and the fact that, in pots at least, they grow slowly and take up little space. Cacti are also generally easy to care for and can survive long periods of neglect. In fact, a cactus is a veritable model of resiliency.
Cacti generally have fleshy stems, brilliant flowers, and spines instead of leaves. Often, terms such as "skin," "flesh," "hair," "spine," "joints," "cuticles," and "ribs" are used to describe cacti, terms we also use to describe people. It's as if the cactus is the human being of the plant world.
I asked Knapik to list a few of his favorite cactus groups and to tell me why he thought they were exceptional.
"We have one cactus along the border of our country," Knapik began. "It's called Ariocarpus, and it's one of my favorite cactuses because it has no spines. It has these very modified tubercles where the spines normally would have come out and little wooly tufts. They look like stars. They're absolutely stunning. It's an untraditional cactus, and people are usually surprised how beautiful and symmetrical they are. I've seen them in habitat, and when you find one, it's like you've found gold."
Knapik went on. "The Astrophytum group has beautiful forms. The bishop's cap is a famous Astrophytum that doesn't have any spines, and it's shaped like a star, and it has this white flecking all over it. The Japanese have revolutionized the Astrophytum group with some of their hybrids. They've produced a hybrid called 'Super Kabuto' -- and there are clubs in Japan that focus only on this hybrid -- and some of these plants sell for thousands of dollars. They look absolutely fantastic.
"My other favorite cactus is the Copiapoa," said Knapik. "I've been to Chile three times to see them in habitat. They form mounds that are four or five feet tall and ten feet across, and the body of the plant is bluish gray, and their spines are black, and the number of heads could be hundreds, and they can live to be 500 years old. And they're fantastic. They're absolutely the most stunning plants I've ever seen in the wild. I go to Chile to photograph them.
"The Lophophora group are also very advanced and very beautiful," Knapik concluded. "This is the peyote group, and they've developed alkaloids in their tissue, which prevents animals from eating them. They've gone beyond spines; they don't need spines anymore. It's a beautiful plant, but unfortunately most of the species are banned because of the drug implications."