These plants kill quickly. Others work their evils more slowly. For instance, bracken fern, if eaten the way people prepare fiddlehead ferns in spring, is carcinogenic. So is tansy ragwort, which can do its damage through prolonged contact - you don't have to eat it to feel its effects.
Some plants can have drastic effects that stop short of death. Nibble on a dieffenbachia leaf, some calladium or rhubarb leaves, and the oxalic acid crystals they secrete will paralyze your vocal chords - but it may only be temporary.
The list goes on and on. It can make a garden sound like a lovely death trap.
Is all this death and destruction some evil trick of nature? Not really. Poison is nature's way of protecting her plants, which, rooted in the earth as they are, cannot fight back when some hungry herbivore approaches to rob them of their greenery.
Many poisonous plants are very bitter-tasting, both as a warning to us, and as a way of discouraging further grazing. Some plants are extremely clever in the timing of their toxicity. Tomatoes, for instance, contain tomatine, which causes intestinal irritation. This discourages critters from eating them before they have a chance to ripen and spread their seed, thus ensuring the survival of the species. Once ripe, they are also not only safe but, as we well know, very good to eat.
Other plants transfer their poison to animals to help them protect themselves. The Monarch butterfly gets its toxicity from the milkweed, whose sap is mildly poisonous even to humans. This gives the butterfly a repellant, bitter taste which protects it from being some bird's breakfast.
Plants don't become the enemy just because they defend themselves from predators. Yet they are clearly dangerous. So what do we do - ban them from our yards?
I don't think so.
You probably played with the buttercup the same as I did - and we're both still here. I doubt that our mothers ever even thought to tell us to "please don't eat the rhododendron." That would be akin to telling kids not to put beans in their ears.
They probably did warn us not to eat, or even play with the fascinating seeds of the castor bean, one of the most highly toxic substances available. More likely, they didn't plant anything poisonous that was likely to fascinate small children. The less fascinating plants taste awful, and so kids are unlikely to do more than take a tiny nibble, make a face then spit it out. Tiny quantities of most plants will do no harm. After all - how many of us have swallowed apple seeds and lived to tell the tale? I know I have. But my mother didn't quit buying them because of their dangerous seeds, either.
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