I am about to do in a plant with which I’ve had an uneasy relationship for some time: a specimen of Conium maculatum or poison hemlock. It’s famous for having produced the substance that killed Socrates, and because of this remote association, I was quite surprised to discover that it’s relatively common where I live and garden. It was even more of a surprise when one appeared in my garden a few years ago. The definitive  identifier is the purple spots on the stems, which explain the species name — “maculatum.” (Think of the word “immaculate,” one of whose meanings is “unspotted.” So interesting!)

Once I knew what it was, I took a photo of it, dug it up and disposed of it.

This spring, it came back, in exactly the same spot. I suspect that it re-grew from a root fragment left behind. From sheer laziness, I let it grow from a fern-like clump of basal leaves into a statuesque, branching creature, filling out and preparing to bloom. Now that it’s blooming, the time has come. Letting it set and ripen seed would be most inadvisable.

Plants known to be poisonous make gardeners nervous. From rhubarb leaves to aconites and hellebores, many common garden plants are toxic to some degree. I was surprised to see the castor bean plant, Ricinus communis, growing in public parks. It is handsome, with its large, red-tinted leaves, but is also reputed to be the world’s most poisonous plant. The toxin is concentrated in the bean-like seeds, and it may be that in the northern hemisphere the seeds are rarely produced, avoiding the possibility of ingestion by members of the wandering public.

Henry Mitchell observed in an essay on fall-blooming bulbs, “Some people get upset about poisonous plants, yet those of us who are not forever gnawing on flowers need not be deterred. It is startling that people accept that war, automobiles, and power mowers are ordinary hazards, but begin to fidget if there is a colchicum somewhere, as if it might attack or poison one while dozing.”

That’s the thing — poisonous plants must be ingested, or at least touched, in order to do harm. Poison hemlock has been mistaken for parsley, and it appears that animals will occasionally eat it. Yesterday the neighbourhood buck was back in my garden. He nipped the tops off some pea plants that were about to bloom. So much for peas this year, but even so I wouldn’t want the creature to eat poison hemlock. I have always thought poisoning to be a particularly nasty way to die. Poison hemlock is said to cause “ascending muscular paralysis,” which causes death when the respiratory muscles are affected. No convulsions or foaming at the mouth, but still an unpleasant way to go.

So later today I will cut down the plant and dig up as much of the roots as I can track down.  I’ll put the thing in a bag and deposit it in the garbage, thus violating the “no organic matter in the garbage” rule. But I don’t think as toxic a plant as this should be blithely put into compost, either domestic or municipal.