Carolina horse-nettle (Invasive Plants of Maryland)

Carolina horse-nettle

Solanum carolinense

Summary ⁹

Solanum carolinense, the 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 much of temperate North America. It has also been found in parts of Europe, Asia, and Australia. The stem and undersides of larger leaf veins are covered with spines.

Description ¹⁰

This native perennial plant is up to 3' tall, branching occasionally. The stems have scattered white or yellow spines. The alternate leaves are up to 6" long and 3" across, and have short petioles. They are broadly lanceolate or ovate, but rather angular along the margins, which are slightly ciliate. There are white hairs and scattered spines along the central vein on the underside of each leaf. The upper stems terminate in small clusters of star-shaped flowers with hairy pedicels. These flowers are white or light violet, about ¾" across, and have 5 petals that are united at the base. Near the center, there are 5 elongated yellow anthers that are very prominent. There is no noticeable floral scent. The blooming period can occur from early summer to early fall, and typically lasts about 1½ months. Afterwards, round fruits develop that are a little more than ½" across and half-enclosed by a papery calyx. They become yellow when mature, but are not edible to humans. Each fruit contains numerous seeds that are glossy yellow and flattened. The root system has creeping underground rhizomes, which are responsible for the vegetative spread of this plant. Cultivation

Ecology ¹¹

These plants can be found growing in pastures, roadsides, railroad margins, and in disturbed areas and waste ground. They grow to about 1 m (39 in) tall, but are typically shorter, existing as subshrubs. They prefer full sun, but can tolerate both wet or dry conditions. They grow readily in sandy or loamy soils, and may also tolerate a wide range of soil types. They are most vigorous and most likely to become weedy or dominate on disturbed sites, but can also be found in less disturbed habitats.

Bumblebees pollinate the flowers of this species.

At least thirty-two insects, as well as the meadow vole Microtus pennsylvanicus, have been recorded feeding on this species in Virginia alone. The caterpillars of the Synanthedon rileyana moth and the Manduca sexta (tobacco hornworm) moth feeds on the plant. Manduca sexta moths prefer inbred plants to outbred plants. The beetle Leptinotarsa juncta specializes on this plant, and the beetle Epitrix fuscula (eggplant flea beetle) eats it as well. These two beetles are its two primary herbivores, and can reduce fruit production by as much as 75% relative to plants protected from all insects. Anthonomus nigrinus feeds on the flowers, and Trichobaris trinotata bores into the stems. This plant is also eaten by Leptinotarsa decemlineata (the Colorado potato beetle) and has been recorded as being eaten at very low rates by pupae of an unidentified species of the family Gelechiidae.

Parasitic nematodes of the genus Pratylenchus have been found on lesions on its roots, however causing little damage. The fungus Rhizoctonia solani was found causing root rot, particularly under wet conditions in plants damaged by trampling. The plant is also affected by Erysiphe cichoracearum, causing downy mildew.

Fruits are eaten by a variety of native animals, including ring-necked pheasant, bobwhite, wild turkey, and striped skunk. Most mammals avoid eating the stems and leaves due to both the spines and toxicity of the plant.

Toxicity ¹¹

All parts of the plant, including its tomato-like fruit, are poisonous to varying degrees due to the presence of solanine glycoalkaloids 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.

Weed ¹¹

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 glyphosate 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.

Sources and Credits

(c) zen Sutherland, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/54289096@N00/3632402912
(c) Kala Murphy King, some rights reserved (CC BY-NC-ND), uploaded by Kala Murphy King
(c) Lori A Owenby, some rights reserved (CC BY-NC), uploaded by Lori A Owenby
(c) Dorit Eliyahu, some rights reserved (CC BY-NC), uploaded by Dorit Eliyahu
(c) tsc_wis, some rights reserved (CC BY-NC)
(c) Kenneth Bader, some rights reserved (CC BY-NC), uploaded by Kenneth Bader
(c) Sara Rall, some rights reserved (CC BY-NC), uploaded by Sara Rall
(c) mmn_noriko, some rights reserved (CC BY-NC), uploaded by mmn_noriko
Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Solanum_carolinense
(c) John Hilty, some rights reserved (CC BY-NC), http://eol.org/data_objects/29442841
(c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Solanum_carolinense

More Info

iNat Map

Flower color	white
Special status	MD noxious weed

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