|Young plant showing leaves and flowers. Notice the spines on the stem.|
Solanum carolinense, Carolina horsenettle is not a true nettle, but a member of the Solanaceae, or nightshade family. It is a perennial herbaceous plant, native to the southeastern United States that has spread widely throughout North America. This plant has hard spines along the stems that can penetrate the skin and break off, causing much pain.
"Horsenettle" is also written "horse nettle" or "horse-nettle", though USDA publications usually use the one-word form. Though there are other horsenettle nightshades, S. carolinense is the species most commonly called "the horsenettle". Other common names include radical weed, sand brier or briar, bull nettle, tread-softly, apple of Sodom, devil's tomato and wild tomato.
Leaves are alternate, elliptic-oblong to oval, 2.5 to 4.5 inches long, and each is irregularly lobed or coarsely toothed. Both surfaces are covered with fine hairs. Leaves smell like potatoes when crushed. The flowers have five petals and are usually white or purple with yellow centers, though there is a blue variant that resembles the tomato flower. The fruits also resemble tomatoes. The immature fruit is dark green with light green stripes, turning yellow and wrinkled as it matures. Each fruit contains around 60 seeds. It flowers throughout the summer, from April to October. The plant grows to 3 feet tall, is perennial, and spreads by both seeds and underground rhizome. Stems of older plants are woody.
All parts of the plant are poisonous to varying degrees due to the presence of solanine which is a toxic alkaloid and one of the plant's natural defenses. While ingesting any part of the plant can cause fever, headache, scratchy throat, nausea, vomiting, and diarrhea, ingesting the fruit can cause abdominal pain, circulatory and respiratory depression, or even death.
These plants can be found growing in pastures, roadsides, railroad margins, and in disturbed areas and waste ground. They grow to about 1 m tall, but are typically shorter, existing as sub shrubs. They prefer sandy or loamy soils.
Carolina horsenettle is considered a noxious weed in several US states. It can spread vegetatively by underground rhizomes as well as by seed. It is resistant to many postemergent herbicides and somewhat resistant to broad-spectrum herbicides such as glyphosphate and 2,4-D. In fact, herbicide use often selects for horsenettle by removing competing weeds. It is an especially despised weed by gardeners who hand-weed, as the spines tend to penetrate the skin and then break off when the plant is grasped. The deep root also makes it difficult to remove.
Solanum pumilum (as described by Michel Félix Dunal) was considered a variety hirsutum of the Carolina Horsenettle by D'Arcy and A. Gray. Several other varieties and forms of S. carolinense are not considered taxonomically distinct nowadays:
- Solanum carolinense f. albiflorum (Kuntze) Benke
- Solanum carolinense var. albiflorum Kuntze
- Solanum carolinense var. floridanum (Dunal) Chapm.
- Solanum carolinense var. pohlianum Dunal
- Solanum floridanum Raf.
- Solanum floridanum Shuttlew. ex Dunal (non Raf.: preoccupied)
- Solanum godfreyi Shinners
- Solanum pleei Dunal
- Bradley, Kevin W.; Hagood, Edward S. "Identification and Control of Horsenettle ( Solanum carolinense ) in Virginia". Retrieved 6 October 2013.
- Georgetown University Medical Center
- Solanaceae Source 
- Solanaceae Source : Solanum carolinense. Retrieved 2008-SEP-26.
- Georgetown University Medical Center : Horse Nettle. Retrieved 2013-JUN-25.
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