Solanum nigrum - black nightshade
Black nightshade is an annual that reproduces by seed. It is an abundant weed in the Willamette Valley, although for some reason, I see it far less commonly in nursery crops than its close relative, hairy nightshade.
There is no agreed upon derivation for the generic name of this plant. Clark suggests that it may be derived from the word solamen, which means soothing (Clark, Lewis J., Wild Flowers of the Pacific Northwest). Soothing would be appropriate considering the narcotic and toxic qualities of the plants foliage and berries. The plant contains high levels of a bitter and toxic alkaloid called solanine.
Leaves are alternately arranged along the stem, slightly lobed, and dark green in color. The leaf surface is scabrous to slightly pubescent.
Stems are scabrous, but not nearly as hairy as those of hairy nightshade. Stems are completely herbaceous and slightly ridged.
Flowers occur in internodal clusters, often hidden by plant foliage.
Flower have 5 white petals, 5 sepals, and many yellow stamen that surround a single pistil.
Fruit are berries that are initially green but mature to black.
Berries in the following two images show sepals of different shape and size. Sepals of black nightshade vary in that they are sometimes pointed and other times rounded, but are small compared to those of hairy nightshade.
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