Solanum americanum
Solanum douglasii
American black nightshade, American black or common or West Indian nightshade, glossy nightshade, little white nightshade, small-flower nightshade, white nightshade
Douglas' nightshade, greenspot nightshade
petiolate;
petiole 1–4 cm;
blade simple, ovate to ovate-elliptic, 2–10.5 × 1–4.5 cm, margins entire or shallowly sinuate-dentate, base decurrent.
petiolate;
petiole 0.5–3(–7) cm;
blade simple, ovate, 1–5(–9) × 0.5–3(–6) cm, margins entire to coarsely and irregularly toothed, base truncate to acute and decurrent.
extra-axillary or leaf-opposed, unbranched, usually umbel-like, 3–10-flowered, 0.5–3 cm.
extra-axillary or leaf-opposed, unbranched, racemelike, 2–7(–14)-flowered, 2–4 cm.
erect or spreading, 0.3–1 cm in flower, to 1.5 cm in fruit.
0.5–1 cm in flower and fruit, nodding or deflexed downward in fruit.
radially symmetric;
calyx somewhat accrescent, unarmed, 1–3 mm, lobes deltate, strongly reflexed in fruit;
corolla white, sometimes with yellowish central star, stellate, 0.4–0.8 cm diam., without interpetalar tissue;
stamens equal;
anthers ellipsoidal, 0.7–1.5 mm, dehiscent by terminal pores that open into longitudinal slits;
ovary glabrous.
radially symmetric;
calyx not accrescent, unarmed, 2–3 mm, sparsely pubescent, lobes deltate;
corolla white with yellow-green to brownish central star, stellate, 1–2 cm diam., without interpetalar tissue;
stamens equal;
anthers ellipsoidal and slightly tapered towards the tips, (2.5–)3–4.5 mm, dehiscent by terminal pores that open into longitudinal slits;
ovary glabrous.
shiny purplish black, globose, 0.5–1 cm diam., glabrous, with (0–)2–4(–6) sclerotic granules, usually 2–4 larger and 2 smaller.
dull purplish black, globose, 0.5–1 cm diam., glabrous, with (2–)6–8 sclerotic granules per fruit.
pale yellow to brown, 1–1.5 × 0.5–1.5 mm, minutely pitted.
pale yellow to tan, flattened, 1.5–2 × 1–1.5 mm, finely reticulate.
= 24.
= 24.
Solanum americanum
Solanum douglasii
Solanum americanum is a morphologically variable and globally distributed weedy species. It has often been confused with other species in the black nightshade group such as S. emulans, S. nigrescens, S. nigrum, and S. pseudogracile and has often been referred to as S. nodiflorum in floristic treatments. It is distinguished by its very short anthers and shiny black mature fruits with strongly reflexed calyx lobes and usually two to four (rarely none or as many as six) sclerotic granules per fruit. Leaf shape and pubescence can vary considerably throughout its range, and there are some suspected cases of introgression with other species such as S. nigrescens or S. pseudogracile. The name S. nigrum has been misapplied to S. americanum (for example, A. E. Radford et al. 1968).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Solanum douglasii is most commonly found west of the Rocky Mountains. It can be difficult to distinguish from S. nigrescens, but its longer, slightly tapered anthers on very short (relative to anther length) filaments is a good distinguishing character for plants in flower. The buds of S. douglasii are more pointed than those of S. nigrescens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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