Know Your Natives – Black Nightshade

Black Nightshade (Solanum ptychanthum) of the Nightshade Family (Solanaceae) is a common weedy native with small white flowers and black berries. The genus name, meaning “quieting,” is the classical Latin name for the nightshades, in reference to the narcotic properties of some species of the genus.* The specific epithet is formed from the Greek for “folded flower.” In the U.S., Black Nightshade is widespread, growing from south Texas to North Dakota, east to the Atlantic Coast. Occurrence in Arkansas is statewide. The species is also known as Eastern Black Nightshade and West Indian Nightshade. Habitats, often weedy, include sites with variously moist soils in full to partial sun, such as open woodlands, forest edges, thickets and croplands.

This annual or short-lived perennial species has a whitish, rather gnarled, branching taproot. Stems are erect when young but can become low-growing as they divide and lengthen. A mature plant, with several slender stems, may be only 6+ inches tall and 3 feet wide. Flowers are produced from June into October, with fruits until frost. Although plants have an overall leaf-and-stem pattern that is alternate, nodes may bear a whorl of one or two branches with or without leaves. Stems are medium green (aging gray-brown), glabrous or minutely pubescent (velutinous), and round in cross-section.

Photo 1: This annual low-stemmed plant has a stout gnarly rootstock (taproot cut off).
Photo 2: Young green stems have straight segments between leaves or branches with slight ridges extending below leaf bases. Lower portions of stems and branches of mature plants are a striated gray-brown.

Leaves are simple, mostly alternate, petiolate, and broadly lanceolate to deltate, with acuminate, blunt tips and rounded to wedge-shaped (cuneate) bases. Petioles are partially winged by extensions of the leaf blade. Leaves, to 3 inches long (including petioles of ¾ inch) and 2 inches wide, are widest at and below the middle. Surfaces are medium green above and lighter beneath; like the stems, they are glabrous to minutely pubescent. Margins are entire to broadly undulate or bluntly dentate.

Photo 3: Most leaves have broadly undulate to bluntly dentate margins. Petioles are partially winged.
Photo 4: Pinnate leaf venation is slightly recessed on the upper surface (see Photo 3) and expressed in round-relief on lower surface. Lowers surface of blades, petioles, and upper branches are velutinous.

The inflorescence consists of small umbels growing directly from branches (not axillary or terminal). Peduncles (stalks of umbels) are ¾+ inch long and extend straight-out from the branch, while the pedicels, to 1/3 inch long, arch downward. Umbels have 2-6 (often 3) flowers. Peduncles and pedicels tend to be velutinous.

Flowers, ¼+ inch across, have a tight tubular calyx with 5 stubby triangular lobes and a sympetalous corolla of 5 narrowly triangular lobes. At anthesis, the star-shaped corolla of the pendant flower is strongly reflexed. Corolla lobes are a dull white overall, with shiny bright green flaring-out from the center. A central ring of five adnate, bright yellow, tubular anthers protrudes prominently from the corolla. The anther ring tightly encloses and hides the style, with only the small knob-like stigma exposed. Anthers have terminal pores for pollen release (poricidal dehiscence). When foraging bees settle on the flower, their buzzing vibrates the anthers, and pollen is released via the apical pores to be collected by the bees or become airborne. Pollen readily adheres to the sticky stigmas. Flowers do not produce nectar.

Photo 5: Upper leaf surface has sparse, non-stellate pubescence, concentrated along the midrib. Tight tubular calyxes have 5 lobes. Umbels grow directly from branches (not axillary or terminal).
Photo 6: Stems and branches of mature plants are low-growing. Leaf beetles forage on leaves.
Photo 7: Corolla lobes become strongly reflexed so that the anther ring is prominent. Yellow anthers are about ⅓ as long as the slender yellowish green filaments. Stigma is barely exposed beyond the ring of anthers.

Fertilized flowers produce dangling spherical berries into late fall. A robust plant has the potential to produce 100+ berries. Berries, at first a mottled pale green, become solid black at maturity. The green star-like calyxes persist at the base of the shiny ¼-inch fruits. Berries contain to 75+ discoid tan seeds to 1/16 inch across in a gelatinous clear liquid.

Photo 8: Persistent calyxes subtend the spherical berries. Peduncles and supporting branches may have velutinous pubescence while upper leaf surfaces tend to have longer hairs.

For an informal garden or natural area, this annual prickle-free species may be appropriate. It grows well in a sunny to partially shady site. While plants may be aggressive, relatively large leaves, tiny flowers and black fruit do provide interest. Plants are classified as toxic to foraging animals, and green, immature berries contain solanine and should be avoided by people. Mature fruits and seeds are a food source for song and game birds and small mammals. Foliage is eaten by leaf beetles (Chrysomelidae family). Seed dispersal is by the bird and mammal foragers.

Photo 9: 1/4-inch spherical berries contain numerous 1/16-inch discoid seeds in a clear gelatinous liquid.

In addition to Black Nightshade, six additional species of Solanum occur in Arkansas. Black Nightshade is the only prickle-free species with small black fruits. One species, Carolina Horse Nettle, has been previously addressed in a “Know Your Natives” article.

*Plants in the Solanum genus (including tomatoes, potatoes and eggplants) contain solanine, a natural defense for the plants. Concentration of solanine varies by species and by plant part. Green fruit tends to have the greatest concentration.

Article and photographs by ANPS member Sid Vogelpohl

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