Ohio Perennial and Biennial Weed Guide

Family:

Nightshade Family (Solanaceae)

Other Names:

apple-of-Sodom, ball nettle, bull nettle, devil's-potato, devil's-tomato, sand brier, wild tomato.

Origin and Distribution:

Horsenettle is a native of southeastern U.S. with a current range extending north as far as Canada and west to Texas. The species occurs in every county of Ohio. Horsenettle can be found in old fields, pastures, orchards, roadsides, and waste places. Also, it is being encountered with increasing frequency in agronomic cropping systems. Horsenettle grows in a wide range of soil types, but it thrives in gravelly or sandy soils.

Plant Description:

Characteristics distinguishing horsenettle from other nightshades are its perennial spreading roots and prickly stems and leaves. Another distinctive feature is the yellow fruit, which changes from plump and smooth-skinned to wrinkled as it matures. New plants arise from seeds and spreading underground roots, which generally produce numerous shoots in dense patches.

• Root System:

  The root system is composed of deeply penetrating vertical roots, which grow as long as 10 feet, and spreading horizontal roots that extend up to 3 feet and are capable of producing new shoots.

• Seedlings and Shoots:

  The first true leaves formed after a seedling emerges have short stiff hairs on the upper surface. Upper and lower surfaces of subsequent leaves are covered with prickles and star-shaped hairs. Stems of young plants are also covered with prickles and hairs. Foliage emits a characteristic potato odor when crushed.

• Stems:

  Stems are 1 to 4 feet tall and covered with numerous star-shaped hairs and sharp yellowish prickles. Stems are either simple or have a few branches near the top.

• Leaves:

  Leaves are alternate (1 leaf per node), egg-shaped, 2 to 5 inches long, and resemble a small poinsettia leaf. Both upper and lower leaf surfaces have star-shaped hairs and there are prominent yellowish spines on leaf veins, midribs, and stalks (petioles). Edges of some leaves are shallowly lobed.

• Flowers:

  Flowers consist of 5 pale lavender (rarely white) petals that are united at the base, deeply 5-lobed and shaped like a star at the top, and less than 1 inch in diameter. Emerging from the center of each flower is a yellow column composed of fused anthers. Flowers attach laterally to the stem in clusters.

• Fruits and Seeds:

  Fruits are yellow berries that are about 1/2 inch in diameter. When first formed, berries are smooth-skinned and resemble small, plump, yellow tomatoes. As they mature, berries become wrinkled. Berries are borne in clusters. Each berry contains between 40 and 170 yellow, disk-shaped seeds.

Similar Species:

Buffalobur (Solanum rostratum) is also hairy and has prickles, but it is an annual that has leaves with much deeper lobes than horsenettle, bright yellow flowers, and brown spiny berries. Perennial groundcherries (Physalis spp.) are similar to horsenettle in appearance except they lack prickles, have yellow flowers, and form berries enclosed in papery pods.

Biology:

Flowering begins in June and continues until frost. Wrinkled yellow berries may remain attached to stems throughout the winter. A single plant can produce up to 5000 seeds. Seeds buried in soil for up to three years were capable of germinating. New plants also arise from root fragments. Soil disturbances such as tillage and cultivation tend to fragment roots and increase the number of newly emerging plants. Horsenettle is fairly drought resistant because the penetrating roots can grow 10 feet deep. Deep roots also increase the likelihood of surviving over winter. Horsenettle causes indirect damage to crops by serving as an alternate host for diseases such as tomato leafspot and mosaic viruses of tomato and potato. It also serves as a secondary host for Colorado potato beetle. To control underground roots, deep hoeing is required.

Toxicity:

Horsenettle fruits and foliage can poison livestock due to the presence of an alkaloid that must be digested before it becomes dangerous. Content of this toxin increases over the course of the growing season. Drying does not reduce its effect. Poisoning of cattle, sheep, and deer have been reported. However, livestock are rarely poisoned because large quantities must be eaten and horsenettle is too prickly to be relished unless more palatable herbage is unavailable. Symptoms vary among species and can lead to death. Mature fruits of horsenettle are toxic to humans. A child died a few years ago in Philadelphia as the result of eating horsenettle fruits.

Facts and Folklore:

• Horsenettle has been used medicinally to treat epilepsy, asthma, and bronchitis.