Veterinary Medicine Library

Nightshade, Bittersweet (Solanum dulcamara L.)

| Description | Distribution | Conditions of poisoning | Control | Toxic principle | Clinical signs | References


nightshade

Description

About 1,500 Solanum species exist in the world, and they include some of the most common garden plants such as potato (Solanum tuberosum L.) and eggplant (Solanum melongena L.). One of the species, Jerusalem cherry (Solanum pseudocapcicum L.) is grown as a house plant for its compact form and small round berries which turn bright red at maturity. The tomato (Lycopercison esculentum Mill.) is also a related plant. Included in this entry are descriptions of Black Nightshade, Bittersweet Nightshade, Silverleaf Nightshade, and Horse Nettle. Other related species may be found under their own names.

 

Bittersweet Nightshade (S. dulcamara)

Bittersweet nightshade is also known as European bittersweet or climbing nightshade. This plant grows from rhizomes and is a slender climbing or trailing perennial reaching 6 feet in length. Leaves are alternate, ovate, simple or deeply lobed, 1-1/2 to 4 inches long, and pointed at the tip. Flowers are deep purple or bluish purple with flower stalk arising between the leaf nodes or opposite the leaves. Nearly round fruits turn red when mature and stay on the vines through mid winter.

Black Nightshade (S. nigrum)

Black Nightshade (S. nigrum)

Black nightshade is an annual herb with a tap root. Stems are erect and much branched reaching 3 feet tall. Leaves alternate, ovate or lanceolate, and long-stalked. The flower has 5 white petals, sometimes with a yellow inner star, and ranges from 1/4 inch to 3/8 inch across. Berries are round and about 1/4 or so inches across, green, and turn purplish to black when ripe. Immature berries and foliage are toxic, but ripe fruits are reportedly edible.

Plants commonly known as back nightshade may include two native species, American Black Nightshade (S. americanum P. Mill.) and Eastern Black Nightshade (S. ptycanthum Dun.), as well as S. nigrum which was introduced from Europe and is widely naturalized. Solanum ptycanthum may be more commonly found in the midwest since S. americanum appears to be more concentrated in the southern states.

Horse Nettle, Bull Nettle (S. carolinense)

Horse Nettle (S. carolinense)

A perennial with a deep taproot and rhizome below ground. Its stem and leaves have yellowish spines and sometimes are hairy. Leaves are alternate and ovate with irregularly wavy or lobed margins. Flowers appear in June to August, are light purple to white, 3/4 to 1 inch across, and in short racemes near the top of the plant. Petals are united with 5 points at the margin. Fruits are globose, about 1/2 inch in diameter and yellow when mature. Yellow or brownish seeds are numerous, and irregularly circular, about 1/8 inch across.

Silverleaf Nightshade or White Horse-Nettle (S. eleagnifolium)

This perennial herb gets its common name because of its silvery appearance caused by the numerous fine hairs. Its thick, lanceolate leaves are wavy and roughly indented (sinuate). The stems and parts of the leaves have short stiff spines. The flowers appear at the end of branches and have petals which are pale to deep blue or lavender in color.

Jerusalem Cherry (S. pseudocapsicum)


Distribution

Black Nightshade

The native species, S. americanum, is usually found in undisturbed habitats or moist open woodlands, stream banks, valleys, fields, roadsides and waste places throughout the east central United States from Maine to Florida and west to Minnesota, Nebraska and Oklahoma. It is found in almost all counties of Illinois. The introduced species, S. nigrum, is rare in Illinois but abundant in some places from Minnesota and the Dakotas to Oklahoma.

Bittersweet Nightshade

An introduced species from Eurasia, this plant is found in moist ground of low woods, roadsides, fence rows and thickets. It ranges from Nova Scotia to Minnesota through much of the Midwestern states and south to Florida and Texas. In Illinois, this plant is commonly found in the north-eastern counties including Champaign.

Horse Nettle, Bull Nettle (Solanum carolinense L.)

This plant is found in waste spaces or neglected fields, gardens, and roadsides from the Atlantic coast to Texas, north to South Dakota and as far south as Florida. It is a common weed in all counties of Illinois.

Silverleaf Nightshade or White Horse-Nettle (S. eleagnifolium)

Silverleaf Nightshade is found in large colonies in open woodlands, pastures, stream valleys, roadsides and disturbed or waste grounds in the Southwest from Missouri to Kansas, Oklahoma, Texas, Arizona, New Mexico and southwestern Colorado. This plant is found in a a few counties of Illinois, but a similar species (S. carolinense) is easily mistaken for this plant.


Conditions of poisoning

Poisoning by these Solanum species occurs primarily when animals are confined in overgrazed fields or where nightshade is abundant. The hazard of poisoning varies depending on the plant species, maturity of plants, and other conditions.

Generally, the leaves and green fruits are toxic. Ingestion of juice from wilted leaves may be especially toxic and sometimes deadly. Many cases of poisoning have been reported as a result of eating green berries. Green berries have produced severe intestinal, oral and esophageal lesions in sheep. Cattle reportedly seek out the berries of Solanum species and will eat the green plant, specially when other green forage is unavailable. Silverleaf nightshade (S. eleagnifolium) is exceptional in that the ripe fruit is more toxic than the green. S. eleagnifolium is toxic at only 0.1% of the body weight. Toxicity is not lost upon drying. Solanine content increases up to maturity. Solanine, except in potatoes, is reportedly destroyed by cooking. Potato (S. tuberosum) peelings contain the major portion of the toxic principle in the tuber, and leaves, sprouts and vines. Sun-greened potatoes are especially toxic. Spoiled potatoes and peelings also have caused severe poisoning. Cooking does not appear to destroy all the alkaloids in greened potatoes. Toxicity may vary with the soil, climate and other variables. Animals may browse potato plants or eat sprouted potatoes, leading to problems.


Control

Animals should be kept away from fields with heavy infestation of nightshade. Plants should be mowed or pulled up while in flower, and burned. Remove green parts of potatoes before cooking, eat only ripe tubers.


Toxic principle


Clinical signs

Clinical signs vary with irritant effect caused by the intact glycoalkaloid or saponin, and the nervous effects of the alkaloid. Irritant effects include hypersalivation, anorexia, severe gastrointestinal disturbances, with diarrhea that is often early and hemorrhagic. The nervous effects include apathy, drowsiness, depression, confusion, progressive muscular weakness, numbness, dilated pupils, trembling, labored breathing, nasal discharge, rapid heartbeat, weak pulse, bradycardia, central nervous system depression, and incoordination, often accompanied by paralysis of the rear legs. Coma may occur without other nervous signs. High doses may cause intestinal stasis and constipation. Hemolysis and anemia, possibly a result of saponins, have been reported, with renal failure in severe cases. Terminal signs include unconsciousness, shock, paralysis, coma, circulatory and respiratory depression, and death. The course varies from sudden death to 3-4 days of illness which may terminate in death or recovery. in less acutely poisoned animals, there may be yellow discoloration of the skin in unpigmented areas, weakness, incoordination, tremors of the rear legs, anemia, rapid heart rate and bloat.

Other References:

Bittersweet entry in Wikipedia


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