Mexican nightshade, a plant often encountered in various landscapes, belongs to the extensive Solanaceae family, which also includes common garden vegetables. While some members of this plant family are cultivated for food, others, like certain types of Mexican nightshade, contain compounds that can be harmful. Understanding the characteristics of this plant is important for identification and taking appropriate measures when necessary.
Understanding Mexican Nightshade
Mexican nightshade, often referring to species like Silverleaf Nightshade (Solanum elaeagnifolium) or New Mexican Nightshade (Solanum heterodoxum var. novomexicanum), is typically an upright, perennial herb that can reach heights of one to three feet. Its stems are frequently covered with small, sharp prickles and tiny, star-shaped hairs that give the plant a distinctive silvery or gray-green appearance. These hairs are also present on its lance-shaped leaves, which measure between two to six inches long and feature wavy edges.
The plant produces showy, star-shaped flowers that are usually violet-purple or blue, though sometimes white, and are approximately three-quarters to one and a quarter inches across. Each flower has five petal-like lobes that are joined at the base, displaying prominent yellow stamens in the center. These blossoms typically appear from May through October. Following the flowers, the plant develops round berries, which are green when immature, then turn yellow, and can eventually become almost black as they ripen.
These berries, resembling small tomatoes, are about half to three-quarters of an inch in diameter and can persist on the plant for several months. Mexican nightshade reproduces both through seeds and by spreading rootstalks, allowing it to establish and expand in an area. It is native to the southern Plains of the United States and northern Mexico, commonly found in sandy or gravelly soils, dunes, streambeds, washes, and along roadsides.
Toxicity and Safety Precautions
All parts of the Mexican nightshade plant contain solanine, a glycoalkaloid that renders it toxic if ingested. The highest concentrations of this harmful compound are typically found in the ripe fruits and the leaves. Solanine acts as a natural defense mechanism for the plant, affecting cellular and physiological processes in organisms that consume it.
Symptoms of Ingestion
For humans, ingesting Mexican nightshade can lead to a range of symptoms, including:
- Gastrointestinal disturbances: nausea, vomiting, diarrhea, and stomach pain.
- Neurological effects: dizziness, headaches, confusion, delirium, or hallucinations.
- Other signs: dilated pupils, a slow heart rate, low blood pressure, and changes in body temperature like excessive sweating or dry skin.
Pets, including dogs, cats, and livestock, are also susceptible to the plant’s harmful effects. Symptoms in animals often mirror those in humans and can include:
- Dilated pupils, difficulty breathing, excessive drooling, and a reduced appetite.
- Vomiting, diarrhea, confusion, drowsiness, weakness, trembling, and a slowed heart rate.
The severity of these signs can depend on the amount of plant material consumed and which part of the plant was ingested.
Emergency Response and Prevention
If exposure or ingestion is suspected, seek immediate medical or veterinary attention. For human exposure, contact a local poison control center at 1-800-222-1222 in the United States, or emergency services. Do not attempt to induce vomiting unless specifically instructed by a medical professional. If possible, bring a sample of the plant with you to aid in identification.
Treatment in a medical setting may involve:
- Administering activated charcoal to reduce toxin absorption.
- Providing intravenous fluids to combat dehydration.
- Offering oxygen support if breathing is compromised.
- Medications to manage symptoms like abnormal heart rates.
When handling Mexican nightshade, wearing protective gloves is advisable to prevent skin contact. It is also important to keep children and pets away from the plant, especially its attractive berries, to prevent accidental ingestion.
Management and Control
Managing Mexican nightshade involves several approaches to remove it from unwanted areas.
Manual and Cultural Control
For smaller infestations, manual removal by digging or pulling the plants can be effective, especially when the soil is moist. Remove the entire root system, as this plant can regrow from root fragments left in the ground. Frequent and thorough cultivation of the affected area can also help to disrupt the plant’s growth and prevent its return. Another method involves cutting the plants to the ground and then covering the area with heavy-duty woven plastic fabric for at least two years, which can suppress regrowth.
Chemical Control
For larger or more persistent infestations, chemical control options may be considered. Herbicides containing active ingredients such as glyphosate, triclopyr, or imazapyr have shown effectiveness against nightshade. These are best applied to actively growing plants, ideally before they begin to produce berries. When using herbicides, careful application is necessary to avoid harming desirable plants in the vicinity, as some products are non-selective. Always follow the product label instructions for application rates and conditions.
Preventing Spread
Preventing the spread of Mexican nightshade is also a key part of management. Remove plants before their berries mature, as birds can consume and distribute the seeds to new locations. Cleaning gardening tools and equipment after working in an infested area can also help prevent the accidental spread of plant fragments or seeds. For disposal, plant crowns, rootballs, and stems containing berries should be placed in the trash or taken to a designated transfer station, rather than composted, to ensure the seeds do not germinate and create new plants.