I was wandering IKEA with a friend in tow, likely hunting for clothes hampers or single-purpose novelty kitchenware, when I passed a shelf of moon cacti. I’m sure you’ve run into them in your trips to the local hardware store. Or the supermarket. Or anywhere, really; they’re as ubiquitous as Coca-Cola. But, until that moment, I’d never really given them any thought.

What surprised me is that you’re not looking at one organism here.

That lumpy red cap is a cactus unto itself, known as Gymnocalycium mihanovichii. It’s usually born into this world as green and commonplace as the next cactus. But a mutation causes the seedlings to show up red, or orange, or pink. The underlying colors are exposed due to a complete absence of chlorophyll. Of course, a non-parasitic plant sans chlorophyll makes for a short-lived plant, and the seedlings kick off this mortal coil near as quickly as they arrive. Unless, as scientists soon discovered, you shack them up with other plants.

The variety you see quaintly potted near the cash registers is most often grafted to hardy Hylocereus. The two grow together, with the deep green body of the Hylocereus making up for the Gymnocalycium’s chlorophyll deficiency. Over time—usually a few years—the base cactus’ growth outpaces that of the lackadaisical Gymnocalycium, and the strained graft gives up the ghost. But it’s a pretty little marriage, if short-lived. —MN

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