Nightshade

Nightshade, common name for both a family of plants, and for a genus of mostly weedy plants. The family has about 90 genera and 2600 species and includes crop and garden plants—such as potato, tomato, petunia, tobacco, and eggplant—as well as many poisonous plants. The poisonous nightshades contain alkaloids of three major types: tropane, found in belladonna, jimsonweed, and henbane; pyridine, in tobacco; and steroid, in some members of the nightshade genus.

Included in the nightshade genus are such common weeds as horse nettle, a spiny, perennial herb of the south-central to eastern United States; European bittersweet; silverleaf nightshade, a whitish herb of prairies of the southwestern states and Mexico; black nightshade, an annual, self-seeding herb found in disturbed soils of eastern and central North America; and buffalo bur, a spiny weed of the Great Plains and eastward. Also in this genus are the common potato, eggplant, and Jerusalem cherry.

Plants in the nightshade family bear flowers with five sepals, five petals, five stamens, and a solitary pistil that in most species ripens into a berry. In horse nettle, the flowers are white or pale violet, and the berry, yellow; in European bittersweet, the flowers are blue or purple, and the berry, red; in silverleaf nightshade, the flowers are violet or blue and yellow, and the berry, orange; and in black nightshade, the flowers are white, and the berry, black. Buffalo bur has yellow flowers and a spiny fruit or bur resulting from the persistence of the spiny calyx about the berry as it ripens.

The foliage and unripe fruit of most nightshades contain dangerous levels of a steroid alkaloid, solanine. The ripe berries are the least toxic part of these plants but may be deadly under some circumstances. Solanine is also found in potato sprouts and the green spots of some potatoes. A toxic dose of any of these will usually result in severe digestive upset. This may be accompanied by trembling, weakness, difficulty in breathing, or paralysis. Potato sprouts should be removed before using the tubers for food. Potato vines, sprouts, and rotten potatoes should not be used as forage for livestock.

The members of the nightshade family are placed in a medium-size order that includes many attractive spring and summer garden plants. The order is widely distributed, with concentrations of species in the Americas. It contains 8 families and nearly 5000 species. Plants of the order vary greatly in habit, from herbs to trees, and some of them are parasites. The flowers are basically five-parted. The petals are fused into a tube, on the inside of which are borne the stamens.

The morning glory family, with about 1650 species, is a well-known member of the order and contains important food, drug, and horticultural plants. The sweet potato, a member of the morning glory family, is cultivated worldwide; its nutritious tuberous root has been used as a food source since prehistoric times. Other members of the same genus have chemicals similar to LSD (see Lysergic Acid Diethylamide). Still other species of this and other genera provide garden ornamentals, such as the morning glory. The phlox family, which contains about 300 species, provides such ornamentals as Jacob’s ladder and the common annual phlox, native to Texas. The mostly herbaceous waterleaf family also contains about 250 species.

Scientific classification: Nightshades make up the genus Solanum, and the family Solanaceae, in the order Solanales. Horse nettle is classified as Solanum carolinense, European bittersweet as Solanum dulcamara, silverleaf nightshade as Solanum elaeagnifolium, and black nightshade as Solanum nigrum. Buffalo bur is classified as Solanum rostratum, the common potato as Solanum tuberosum, the eggplant as Solanum melongena, and the Jerusalem cherry as Solanum pseudocapsicum. The sweet potato, classified as Ipomoea batatas, and the morning glory, classified as Ipomoea purpurea, belong to the family Convolvulaceae. Jacob’s ladder, classified in the genus Polemonium, and the common annual phlox, classified as Phlox drummondii, belong to the family Polemoniaceae.