The “demon potato” is a common nickname for Solanum carolinense, more widely known as Carolina horsenettle. This perennial broadleaf weed has earned its problematic reputation due to its pervasive nature and ability to thrive in various environments. It is a widespread and challenging weed for gardeners and agriculturalists.
Understanding the Demon Potato
Solanum carolinense, a member of the nightshade family (Solanaceae) which includes potatoes and tomatoes, typically grows 1 to 3 feet tall, sometimes reaching 4 feet. Its stems and leaf undersides have sharp, stout prickles, which can be yellowish and up to 12 mm long. Leaves are alternate, elliptic-oblong to oval, often with irregular lobes or coarse teeth, and covered in fine, star-shaped hairs.
The flowers resemble those of a potato, with five white or pale violet petals and prominent yellow anthers. They bloom from late spring through summer, generally between May and September. The plant then produces round berries, initially green with light stripes, which mature into smooth, yellow, tomato-like fruits (1 to 1.5 cm). Each berry can contain up to 170 seeds.
Carolina horsenettle’s aggressive growth stems from its extensive root system. It has a deep taproot (4 to 10 feet) and horizontal creeping roots (rhizomes) that spread several meters, sometimes over 3 feet per year. This dual reproduction method, through abundant seeds and spreading rhizomes, contributes to its persistence. The plant is highly adaptable, tolerating a wide range of soil conditions, including sandy or loamy soils, and thrives in disturbed areas, pastures, roadsides, and cultivated fields.
Dangers of Demon Potato
The primary danger of Solanum carolinense is its toxicity. All parts, especially unripe berries, contain toxic glycoalkaloids, predominantly solanine. Toxicity levels vary, but solanine concentrations are highest in late summer and fall. Green berries are more toxic than ripe yellow ones, and berries are more toxic than leaves, stems, or roots.
Ingestion can cause significant harm to humans and animals. Human symptoms include nausea, vomiting, abdominal pain, salivation, and drowsiness. The plant’s sharp prickles can also cause skin irritation. Livestock, including cattle, horses, sheep, goats, pigs, and rabbits, are susceptible to poisoning. Animal symptoms range from gastrointestinal issues (colic, diarrhea, salivation) to severe neurological symptoms (weakness, muscle tremors, incoordination, difficulty breathing). In severe cases, ingestion can lead to kidney failure, paralysis, coma, or death. Pregnant cows may also experience abortion.
Beyond toxicity, Carolina horsenettle negatively impacts agricultural fields and pastures. Its aggressive growth and extensive root system outcompete desirable crops and forage, reducing yields and quality. Berries can contaminate harvested crops like soybeans, making separation difficult. The plant also acts as an alternate host for agricultural pests, including the Colorado potato beetle and potato psyllid, which transmit diseases to cultivated potatoes and tomatoes.
Managing Demon Potato
Managing Carolina horsenettle requires persistent effort due to its deep, extensive root system and its ability to reproduce from both seeds and root fragments. Simple tillage can inadvertently spread the plant by distributing root pieces. Therefore, a combination of control methods is necessary for effective long-term suppression.
Manual and mechanical control methods can be effective for smaller infestations. Hand-pulling individual plants is most successful when the soil is soft, such as after rain, and requires removing the entire root system to prevent regrowth. Repeated digging can also reduce populations. Mowing can help prevent the plant from flowering and producing seeds, limiting its spread, but it does not eliminate the deep roots. Consistent mowing every 30 days during warmer months, particularly just after the plant blooms, can weaken root reserves over several years.
Chemical control often provides the most effective management for larger infestations. Systemic herbicides, which are absorbed by the plant and translocated to the roots, are generally recommended. Products containing glyphosate or 2,4-D are commonly used. Application timing is important; late summer or early fall, about two weeks before a killing frost, is often optimal when the plant actively translocates nutrients to its roots. Herbicides like dicamba, triclopyr, aminopyralid, and picloram are also effective, often providing good control when applied at the flower bud stage. Always read and follow product labels for specific application rates, safety, and restrictions.
Cultural practices also contribute to managing Carolina horsenettle by creating conditions less favorable for its growth. Maintaining healthy, dense turf or crop stands can help outcompete the weed for resources. Crop rotation, especially incorporating small grains or perennial forage crops like alfalfa that are frequently mowed, can suppress horsenettle populations. Mulching can also help suppress new growth from seeds. For severe infestations, a comprehensive approach integrating these methods over two to three years is necessary to significantly reduce the weed’s presence.