As is frequently the case with medications, a plant or plant
derivative that is curative in small doses can be poisonous in large doses. There are
relatively few plants that are extremely toxic when ingested in moderate amounts in their
natural state. Some plant parts, however, can cause illness and even death, especially if
ingested by small children.Sometimes plants
considered to have curative properties turn out to have a dark side. Historically, tobacco
was reported to cure colds, toothache, indigestion, cancer, and more. Now the
health-related issues surrounding tobacco are widely known. Incidently, tobacco
derivatives are still used as broad-spectrum insecticides; nicotine is lethal to most
insects as a contact poison.
Here’s a brief list of plants that contain toxic
substances.
Hemlock (Conium maculatum). We
mentioned this relative of dill and carrots in Part I. Hemlock juice was the poison used
to kill Socrates.
Monkshood (Aconitum napellus). A
garden perennial common in temperate regions, monkshood produces spikes of attractive
blue, helmet-shaped flowers. Monkshood, also known as wolfsbane and aconite, contains the
potent alkaloid aconitine, most concentrated in its roots. Aconitine is a potent,
fast-acting central nervous system poison; it was used for centuries as an arrow poison.
Taken in small doses aconitine can inhibit respiration; larger amounts can lead to
complete heart failure. (Ingestion of just a teaspoon of the root can be fatal.)
Oleander (Nerium oleander). This
attractive flowering shrub is native to the Mediterranean region and has been cultivated
for centuries. Brought to North America by the early settlers, it has naturalized in warm
regions of the U.S. Oleander, like other members of the dogbane family, contains potent
poisons. All plant parts are poisonous if eaten, and some people develop a skin rash upon
contact with the plant.
Jimsonweed (Datura stramonium).
Also called angel’s trumpet, thorn-apple, devil's trumpet, and apple of Peru,
Jimsonweed is a member of the nightshade family Solanaceae, and is thus a relative of
peppers, tomatoes, and eggplants. It is a coarse, shubby plant with beautiful, white,
trumpet-shaped flowers that open at night to attract pollinating moths. Daturas contain
three powerful alkaloids—atropine, scopolamine and hyoscyamine—that produce a
strong narcotic effect upon consumption. Symptoms include dilation of the pupils,
giddiness, delirium, and even mania. The whole plant is poisonous, but the seeds contain
the highest concentrations of the active substances.
Belladonna (Atropa belladonna) is another
member of the nightshade family that contains the same three alkaloids. Italian women made
eyedrops from this plant and used them to dilate their pupils, giving them the desired
dark-eyed look. The name belladonna is Italian for "beautiful woman."
We’ve spent quite a bit of time looking at plants and
the important role they play in our lives. Yet we’ve only touched the surface on this
subject—especially when it comes to plants with medicinal properties. You may have
noticed some new products on the shelves at your local grocery store or pharmacy.
Echinacea, from the purple coneflower (Echinacea purpurea) is reputed to enhance
the immune system, and is becoming more and more common in cold remedies. And reports of
the mood-lifting properties of St. Johnswort (Hypericum perforatum) have made it a
popular supplement. Both of these plants are easy to grow—almost weedy—and have
been used for years by herbalists. Time will tell whether this trend toward commercial
manufacturing of herbal remedies is a passing fad or a lasting trend.
In the next section, we’ll be looking at plants in a
different light—one with which we gardeners are very familiar: plants as food.
We’ll begin by looking at individual nutrient categories, and progress to a survey of
the range of plants and plant parts used as food.
