Horse nettle (Solanum carolinense), also known as bull nettle or devil’s potato, is a common plant found throughout much of North America. This perennial member of the nightshade family often appears in disturbed areas like pastures, cultivated fields, and roadsides.
Identifying Horse Nettle
Horse nettle typically grows between 1 and 4 feet tall. Its branched stems have scattered, sharp, yellowish spines, about 0.5 inches long. The leaves are alternate, simple, and irregularly lobed or coarsely toothed, ranging from 2 to 6 inches. They also have fine, star-shaped hairs and often bear prickles on their veins and petioles.
The star-shaped flowers have five petals, typically appearing in clusters. Their color varies from white to pale violet or purple, with five bright yellow anthers forming a central cone. The plant produces small, rounded berries resembling miniature tomatoes, about 0.5 to 0.75 inches in diameter. These berries are initially green with light stripes, maturing to a glossy yellow or orange, often becoming wrinkled.
The Toxic Nature of Horse Nettle
All parts of horse nettle contain toxic compounds, primarily steroidal glycoalkaloids like solanine. Toxin concentration varies, with unripe berries generally most potent, followed by ripe berries, then leaves, stems, and roots. Toxicity can also be higher in the fall. These toxins are not destroyed by drying or cooking.
In humans, ingesting horse nettle can lead to symptoms predominantly affecting the gastrointestinal system, including nausea, vomiting, diarrhea, and abdominal pain. Other symptoms can involve drowsiness, dizziness, dilated pupils, headache, and agitation. Skin contact with the plant’s sap or a thorn puncture can also cause irritation or a rash.
Animals, including livestock like cattle, horses, sheep, goats, and pigs, are also susceptible to horse nettle poisoning. Symptoms can include excessive salivation, colic, diarrhea or constipation, weakness, and ataxia (loss of coordination). Severe cases can lead to nervous system depression, labored breathing, dilated pupils, and potentially death. Though animals often avoid the plant due to its prickles and unpleasant taste, poisoning can occur if other forage is scarce.
Historical and Traditional Applications
Historically, horse nettle was attributed various “uses” in folk medicine by Native Americans and early European settlers. For instance, a tea from wilted leaves was sometimes used as a gargle for sore throats or to expel worms. A poultice from the leaves was also applied to rashes, such as those caused by poison ivy.
The berries and roots were occasionally used for ailments like epilepsy, asthma, and bronchitis. Some historical accounts suggest their use as a diuretic, painkiller, or antispasmodic. Despite these historical mentions, these applications are not supported by modern safety standards. Ingesting any part of the plant can cause severe, potentially fatal, adverse reactions.
Managing Horse Nettle
Horse nettle is a persistent and aggressive weed due to its extensive, deeply penetrating root system, which can reach depths of 8 to 10 feet. It spreads effectively through prolific seed production and creeping rhizomes. A single plant can produce up to 5,000 seeds, and even small root segments can generate new plants.
For small infestations, manual removal can be effective, but requires diligent effort and protective clothing due to the plant’s prickles. Removing the entire deep root system is challenging, as left-behind fragments can resprout. Mowing can help weaken the plant, especially if done frequently after flowering, but typically takes two years or more for significant results. Tillage can inadvertently spread the plant by breaking up and distributing root segments.
Chemical control methods are often employed for larger or persistent infestations. Herbicides with active ingredients like glyphosate or triclopyr are commonly used and most effective when applied during the plant’s active growth stage, typically in late spring or early summer. Due to its robust root system, consistent management over two to three years is often necessary to significantly reduce horse nettle populations.