Eating just a few leaves or berries will leave you writhing on the ground. Your mouth dries, your pupils enlarge, and you run a fever. Within minutes, you gasp as painful cramps turn into vomiting and diarrhea. First your pulse races, then it slows, as does your breathing. Your head pounds, and then the hallucinations start. You’ve become paralyzed.
But soon, none of that matters any more—because you’ll be dead.
Happily, if you do manage to get to a hospital in time, there’s a good chance you’ll recover, although the symptoms can last up to three days. Eating an unidentified plant is never a good idea, but if it happens to be one of the more dangerous members of the nightshade family, it could be fatal.
It’s hard to believe that deadly nightshade (Atropa belladonna), jimson weed (Datura stramonium), and those French fries you had for lunch are all related. It just goes to show that every family has a few members we’d do well to avoid.
The nightshade family, Solanaceae, is large, with around 98 genera and approximately 2700 species. They can be found on every continent except Antarctica, although most are tropical or semi-tropical. They can be vines, shrubs, or trees. Some are epiphytic (they grow on other plants). Many are dangerously poisonous, while others, such as eggplant, peppers, and tomatoes (in addition to the above-mentioned potatoes) are used as food. Tobacco is a member, as are our beloved petunias.
With such diversity, identifying members of the Solanaceae can be tricky, but they do have some common traits. In general, the leaves are alternate, although in some cases they become opposite as you travel up the stem. Break a stem and the juice inside is colorless. Most flowers are complete—e.g., they have both male and female parts—typically with five sepals and five fused petals. Most of the time, the ovary (which becomes the fruit or seed pod) has two parts, which you can see if you cut one in half crosswise.
While all that information is helpful, I find it most helpful to spend some time simply looking at the flowers apart from a close examination. You begin to get a feel for their appearance. Take a look and see what I mean:
It’s understandable that tomatoes were first introduced as an ornamental. So many nightshades produce alkaloids, chemicals that may be highly toxic or psychoactive. While we certainly want to avoid the symptoms of poisoning, many of these compounds are used as pharmaceuticals, such as the anti-nausea drug scopolamine (hyoscine), and atropine, which is used to treat cardiac arrhythmias, digestive problems, and to dilate the pupils for an eye exam.
Nicotine is another alkaloid produced by some nightshades. Nicotine is highly addictive, and the reason it’s so hard to stop smoking, although it is currently being tested as a treatment for a variety of neurological disorders, such as Alzheimer’s disease, Parkinson’s disease, and ADHD. While tobacco has the highest concentrations, a (very) small amount of nicotine is also found in tomatoes, potatoes, eggplants, and green peppers—so small that you’d have to eat ten pounds of potatoes at a single meal for it to have an effect. No, you can’t blame the alkaloids for your pizza cravings.
The nightshade vegetables that we eat are often blamed for causing inflammation, and therefore many people avoid them. But there’s no reason to deprive yourself. Nightshades contain alkaloids, which inhibit the enzyme acetylcholinesterase. This affects the nervous system, which leads to that list of symptoms in the first paragraph.
Acetylcholinesterase inhibitors are not inflammatory. In fact, they may have the opposite effect. Studies are underway to determine if nightshades are anti-inflammatory. (You can learn more about the safety of the nightshades we eat in this very good article.)
Nightshades may be a bit scary, but in addition to providing essential ingredients for much Mediterranean, Asian, and Latin American cooking (where would we be without tomatillos, or chili peppers and their alkaloid Capsaicin?), many family members are valued ornamentals. Avid flower gardeners may recognize these Solanaceae species: Bush violets (Browalia), Calibrachoa, Nierembergia, Schizanthus, and Painted Tongue (Salpiglossis, above), flowering tobacco (Nicotiana), Brugmansia, and Brunfelsia. Nightshades can be beautiful as well as tasty. Try some in your next garden and see if you agree.