I love to forage and southern California, I'm discovering rapidly, is copious with free edibles, many conveniently gushing over cinderblock fences and falling ripe on the sidewalk.

I'm proud to say I haven't returned home yet from a jaunt al fresco without handfuls of figs, oranges, lemons, limes, grapefruits, mangoes, pomegranates, cherries (weird ones with huge pits), grapes, sprigs of rosemary, laurel, dates of different varieties (and stickiness), and cactus pears (whose hair-thorns are godawful).

Today in the nearby arboretum, in the cactus section, the most exotic to me, I tried what I swore was a kind of grape, only it grew on a species of cactus that looked like it was from the moon. Its trunk was thick and chunky and its branches, reaching upwards, were short and thin, with green leathery leaves clinging to them. In all, it reached to just over my waistline. Dangling conspicuously were bundles of reddish-orange grapes.

I'm no great Man of the Earth but I try not to be stupid. When foraging, the general rule I follow is that if it's sweet, it's safe. I remember my botany professor explaining back in my science days that the plant invests valuable energy in producing the fruit precisely so animals will eat it and disseminate the seed.

So I picked a particularly ripe grape and nibbled it, not like a famished rat but just enough to sink a tooth in and taste it. Indeed, it was sweet, even reminiscent in taste of a standard grape. I popped it in my mouth and chewed. I chewed it and I started to swallow it. Suddenly, a burning sensation and the tightening feeling that unripe persimmons give took over. I spat it out, but the scorching spread through my mouth and down my throat.

I swished my mouth out with water. I found a fig tree and, achingly, ate a fig in the hopes the pain would go down with solid food. But it wouldn't. It clung, like it were just below the skin and unpurgeable, especially in the throat. Ahh, the throat! For hours and hours it remained.

Later at home, I identified the succulent as cyphostemma juttae, also known as wild grape and in Afrikaans—because it is native to southern Africa—droog-my-keel, "parch my throat." Right-o.

The grape contains oxalic acid, the same found in rhubarb leaf, and it is toxic. Luckily, a lethal dose would require ingesting more than a single grape and before you could get enough down, your throat would curl and dry up into a cinnamon stick.

Anyway, yes, I learned my lesson

The alien cyphostemma juttae

And its evil little grapes that will set a forest fire to your throat