Horse nettle is a native perennial with spiny stems and leaves; the fruits are toxic and look like tiny yellow tomatoes. Flowers in elongated clusters (racemes) at ends of stems, white to purple, about 1 inch across with 5 united petals, forming a five-pointed star with 5 large, yellow stamens protruding. Blooms May–October. Leaves with pointed lobes (somewhat resembling red oak leaves), with 4 lateral lobes and 1 shallow terminal lobe. Does not have bristles, but stems and midribs of leaves have yellow prickles. Fruit a smooth berry, yellow when ripe, like a tiny tomato, which persists through the winter. Most parts of the plant are toxic if eaten.
Habitat and Conservation
Taxonomically, horse nettle is in the nightshade family (Solanaceae), which is the same family as tomatoes, eggplant, and jimsonweed. Therefore, horse nettle is not technically a "true nettle"; nettles are in a separate family (the Urticaceae). Nettles are infamous for the tiny irritating, stinging hairs on their stems and foliage.
The word "horse," as a plant adjective, implies something large, strong, or coarse. Similar plant names are horse-chestnut, a plant related to buckeyes and not in the beech family like edible true chestnuts; horse gentian, which is in the honeysuckle family and not a true gentian in the gentian family; and horseradish, which, though in the same family as radishes, is considerably stronger than them!
Horse nettle spreads easily by seed and by underground rhizomes and can be a troublesome weed, hard to pull because of its spines and deep roots. Native Americans had medicinal uses for it, but all parts are toxic if eaten, and children have reportedly been killed by eating the fruit.
Horse nettle is related to tomatoes and eggplant, whose fruits are edible because they contain a much greater percentage of carbohydrates, offsetting the presence of toxic alkaloids. Potato is also closely related, but it stores a large amount of carbohydrates in its tubers, rendering them edible. Horse nettle's fruits, however, don't store as many carbohydrates, so they contain a comparatively higher amount of the alkaloids, making them toxic to us.