Cultivated at the Chelsea Physic Garden [in protologue said to “grow naturally in Virginia”], Herb. Miller s.n. (lectotype, designated by Edmonds 1972, pg. 103 [as type]: BM [BM000617683]).

Annual to short-lived perennial herbs up to 1.5 m tall, subwoody at base. Stems terete or somewhat angled with ridges, older stems often appearing spinescent, not markedly hollow; new growth pubescent with simple, spreading, uniseriate 2–8-celled eglandular trichomes 0.2–0.8 mm long, often clustered along the stem angles; older stems glabrescent, with only the trichome bases persisting as pseudo-spines. Sympodial units difoliate, the leaves not geminate. Leaves simple, 3.5–10.5 cm long, 1.0–4.5 cm wide, ovate to elliptic; adaxial surface sparsely pubescent with simple, uniseriate trichomes like those on stem, these evenly spread along the lamina and the veins; abaxial surface similar but more densely pubescent; major veins 3–6 pairs; base attenuate, decurrent on the petiole; margins entire or occasionally sinuate-dentate; apex acute; petioles (0.3–)2.0–3.8(-4.0) cm long, sparsely pubescent with simple uniseriate trichomes like those on stems. Inflorescences 0.6–2.5 cm long, lateral and internodal, unbranched or rarely forked, with (3–)4–6(8) flowers (very rarely with many flowers in unusual many-branched inflorescences) clustered near the tips (umbelliform to sub-umbelliform), sparsely pubescent with simple uniseriate trichomes like those on stems; peduncle (0.5–)1.0–1.8 cm long, delicate; pedicels 3–9 mm long, 0.2–0.3 mm in diameter at the base and 0.4–0.5 mm at the apex, stout, straight and spreading, articulated at the base; pedicel scars spaced 0–0.5 mm apart, clustered at the tip of the inflorescence. Buds broadly ellipsoid, the corolla exserted 1/3 beyond the calyx lobe tips before anthesis. Flowers 5-merous, all perfect. Calyx tube 0.8–1.3 mm long, the lobes 0.3–0.5 mm long, 0.5–0.6 mm wide, broadly triangular with obtuse apices, sparsely pubescent with simple uniseriate trichomes like those of the stem. Corolla 3–6 mm in diameter, stellate, white with a yellow-green central portion near the base, lobed 1/2–2/3 of the way to the base, the lobes 2.0–3.2 mm long, 1.0–2.5 mm wide, strongly reflexed at anthesis, later spreading, densely papillate abaxially with 1–4-celled simple uniseriate trichomes, these denser on the tips and margins. Stamens equal; filament tube minute; free portion of the filaments 0.5–0.8 mm long, adaxially pubescent with tangled uniseriate trichomes; anthers 0.7–1.5 mm long, 0.5–0.6 mm wide, ellipsoid to almost globose and very plump-looking, yellow, poricidal at the tips, the pores lengthening to slits with age and drying. Ovary globose, glabrous; style 2.2–2.6 mm long, densely pubescent with 2–3-celled simple uniseriate trichomes 2/3 from the base where included in the anther cone, almost included to exserted 0.5(–1.0) mm beyond the anther cone; stigma minutely capitate, the surface minutely papillate, green in live plants. Fruit a globose berry, 4–9(–12) mm in diameter, purplish-black at maturity, opaque, the surface of the pericarp markedly shiny; fruiting pedicels 13–18 mm long, ca. 0.7–1.0 mm in diameter at the base and 0.8–1.0 mm in diameter at the apex, stout, straight and spreading, spaced ca. 1(-3) mm apart or tightly clustered, not falling with the fruit, remaining on the plant and persistent on older inflorescences; fruiting calyx lobes not accrescent, the tube less than 1 mm long, the lobes 1(–2) mm long, strongly reflexed at fruit maturity. Seeds 30–50 per berry, 1.0–1.5 mm long, 0.8–1.3 mm wide, flattened and tear-drop shaped with a subapical hilum, pale yellow, the surfaces minutely pitted, the testal cells pentagonal in outline. Stone cells mostly absent (Australia, South Pacific, and South America), but if present (North America, Mexico, Caribbean, Eurasia and Africa) 2–4(6) per berry, 2–4 larger ones >0.5 mm, and two smaller ones <0.5 mm in diameter. Chromosome number: 2n=2×=24 (see Särkinen et al. 2018 for vouchers).

(Figure 5) Solanumamericanum is a globally distributed weed found throughout the tropics and subtropics; it is not clear where it is native, or if this circumtropical distribution is its native range. In the region treated in this monograph it is commonest in Central America and the Caribbean, but is found around the coasts in North America, especially around the Gulf of Mexico and the Pacific.

Solanumamericanum is a weedy species that colonises disturbed soil and it is found in open areas, along roads, treefall gaps and at the back of beaches from sea level to 2,000 m elevation.

United States of America. American nightshade (many sources), American black nightshade (Brown and Brown 1984; NatureServe 2017), Hierba mora negra (Correll and Johnston 1970). Mexico and Central America. Hierba (yerba) mora (many sources). Mexico [Guerrero] Saltonchis (Ignacio 4), [Oaxaca] Moo-jo-chi (Hernández Ortega 62), [Puebla] Pchfux-yáas (Zapotec, Hunn OAX-205), [Quintana Roo] Ik kootz (Maya, Ucán Ek 4390), [Sonora] Chichiquelite (Gentry 1269), [Veracruz] Tomatequelite (Balvanera L. 259), Wal ts’ok (Huastec, Alcorn 2347). Guatemala. [Alta Verapaz] macúy, [Santa Rosa] quilete (Gentry and Standley 1974). Belize. Bocano (Gentry and Standley 1974). Bahamas. Gooma bush, Ink berry (Correll and Correll 1982); gumma bush (Richey 99–712). French Antilles. Agouman, Herbe amère (Sastré and Breuil 2007). British West Indies [St. Lucia] Agouma (Proctor 17826). Trinidad and Tobago [Trinidad]. Agouma (Broadway s.n.).

The leaves are widely used as a potherb in Mexico (“quelite”) and the countries around the Caribbean. Gentry and Standley (1974) state that in Guatemala the “foliage is used as one of the common pot herbs and is consumed in large quantities. It is found in most of the markets.”

LC (Least Concern). Solanumamericanum is a cosmopolitan weed of the tropics and subtropics (see Särkinen et al. 2018). For EOO see Table 6.

Solanumamericanum is the most widespread and common species of the morelloid solanums (see Särkinen et al. 2018), and quite possibly the most widely distributed species in Solanum. It has been implicated as the diploid parent in the polyploid events that gave rise to the species of the Old World (e.g., Edmonds 1977; Poczai and Hyvönen 2011), although this has been disputed (Ma 1995). The name S.americanum has been in common use in North America (e.g., Stebbins and Paddock 1949) for what is now known as S.emulans, but more recently (Schilling 1981) the two taxa have been distinguished and the name S.ptychanthum has been used for the taxon for which the oldest name is S.emulans. The type specimen of S.ptychanthum, however, falls within the variation of S.americanum, so is treated as a synonym here. The application of the name S.americanum to any morelloid species with small anthers from northeastern North America should be viewed with caution.

Solanumamericanum can be easily recognised in fruit by its shiny black berries with small, strongly reflexed calyx lobes that are held on erect or spreading pedicels. In flower, the species has tiny almost globose anthers 0.8–1.5 mm long and short filaments usually less than 1 mm long. It has been often confused with S.emulans and S.nigrescens. Solanumemulans has equally short plump anthers but longer filaments (0.6–1 mm versus ca. 0.5 mm long), matte black or green fruits on deflexed pedicels and calyx lobes that are not markedly reflexed in fruit. Ripe berries of S.americanum are shiny black (but that can be difficult to see in herbarium specimens) and in North and Central America and the Caribbean usually have four stone cells in each. Berries of S.emulans have more than five stone cells. When berries ripen in S.americanum they fall from the plant leaving the stout, spreading pedicels behind, while berries drop off with the pedicels in S.emulans leaving only the peduncles behind in herbarium specimens. This can, however, be difficult to see in specimens with only very old inflorescences.

Solanumnigrescens differs from S.americanum in having larger anthers always more than 2 mm long, matte black or green fruits that are held on spreading or deflexed pedicels that drop with the berry, and calyx lobes appressed to the berry base in fruit. Berries of S.nigrescens have more than 5 (usually 5–6 large and several smaller) stone cells, while plants of S.americanum from this region have 2(-4). Inflorescences of S.americanum tend to be more sub-umbelliform in appearance than those of S. nigrescens, and calyx lobes of S.americanum are strongly reflexed and smaller relative to berry size in fruit. D’Arcy (1974a, b) suggests that S.americanum hybridizes with other diploid species (e.g., S.nigrescens) and that intermediates are common, but did not cite vouchers. Our observations (but see below) are that the two species are usually distinguishable using the characters above.

Some geographical trends in the morphological variation within the species can be observed, where populations along the coast of the Gulf of Mexico appear more hairy with duller grey-green leaf coloration, with more narrow, lanceolate rather than ovate leaves, with racemose inflorescences rather than strict umbels, with more rounded calyx lobes that do not always strongly reflex in fruit, and with generally larger fruits. The small anthers combined with stout and spreading pedicels in fruit that remain on the plant after fruits drop off are strong indications that these populations belong to S.americanum and do not represent a distinct species. Variation appears continuous and could be caused by local introgression from the sympatric diploid species S.pseudogracile or S.nigrescens. Collections with forked inflorescences (Nee & McClelland 60259 from Florida; Dancer s.n. from Jamaica) are likely to be isolated aberrant individuals; in other parts of the world populations of S.americanum with highly branched inflorescences occur (e.g., China, type of S.merrillianum T.N.Liou) indicating that plasticity in this character is not unusual. It may also be that plants from cultivated populations in Asia have been brought with rice cultivation to North America. Plants collected as weeds of rice fields in Louisiana (Ma 1995; E. Shilling, pers. comm.) and identified as S.merrillianum are somewhat intermediate between S.americanum and S.nigrescens and could represent recent homoploid hybrids; preliminary data indicate they are members of the clade containing both those taxa. Further studies using molecular markers and carefully comparing Asian and American populations will be necessary to unravel this enigma.

Manoko et al. (2007) distinguished S.americanum and S.nodiflorum using AFLP markers; we re-examined the material they used and consider the plants they called S.nodiflorum to be S.americanum as defined here, and plants they called S.americanum represent specimens of S.nigrescens (see Särkinen et al. 2018: 61).

Typification details for the many synonyms of S.americanum can be found in Särkinen et al. (2018).

See Suppl. materials 1 and 3.