Anyone with a vegetable or flower garden has probably encountered a prickly weed with white to pale purple flowers with yellow centers. If plants are not removed from their location these flowers develop into yellow fruits resembling cherry tomatoes. This isn’t surprising as they are in the same family.
The plant is horse nettle (Solanum carolinense) and I’m convinced that this common weed could be part of the reason many North Carolinians once thought tomatoes were poisonous. All parts of the horse nettle plant are toxic. The yellow fruits, borne in clusters and strongly resembling tomatoes are very toxic. They are poisonous to livestock too, but animals are smart enough to leave them alone.
When I lived in West Virginia the people there called this spiny demon sand brier. It was probably more prevalent than it is in this locale. I cursed this weed every time we put up hay. My fingers, hands and arms were constantly inflamed from prickles embedded in my skin. Feeding it in winter wasn’t much better.
Surprisingly, nobody that I knew ever had any problems with livestock getting sick. I suppose the animals must not have ingested enough to hurt them. I certainly can’t blame them from picking around the spiny stuff.
Children are especially vulnerable to horse nettle toxicity. The pernicious culprit is an alkaloid called solanine. Fruits are bitter tasting and would not be palatable anyway, but children are smaller. Therefore, they need a smaller dose to be affected.
Common toxicity symptoms are: headache, nausea, vomiting, abdominal pain, and circulatory or respiratory problems. Ingestion of too many berries, particularly late in the season can even cause death. We need to be able to identify it and teach youngsters to avoid eating it even though it looks intriguing. Obviously we eliminate it from around our homes, but it’s common in many places children might play.
Horse nettle leaves remind me of eggplant foliage, another potato family relative. Plants are usually less than two feet tall and somewhat erect. Flowers favor those of potatoes more than tomatoes. This shouldn’t surprise as horse nettle is more closely related to potatoes.
Many gardeners and environmentalists rail on the problems caused by exotic species invading the landscape. I’ve read articles stating that if we just kept our plant selections limited to native species our environment would be better. Well, horse nettle is a native plant. It’s a perennial weed common throughout most of the country.
Many common broadleaf herbicides will control horse nettle. A combination of 2,4-D and dicamba works fairly well. The problem is that horse nettle has an extensive underground system of roots and rhizomes. Often chemicals will kill the above ground portions of the plant but those parts underground are less affected.
Additionally, failing to remove plants from the area means they will likely spread from copious amounts of seed. My recommendation is to learn to recognize this plant when it is young and physically or chemically remove it as soon as possible. Spines are less objectionable when plants are young.
Ted Manzer teaches agriculture at Northeastern High School (firstname.lastname@example.org).