United States of America. North Dakota: nr. Fort Mandan, Anon. [Lewis & Clark] s.n. (lectotype, designated by Barboza et al. 2013, pg. 260: PH [PH00030496]).

Annual herbs to 40 cm tall, much branched at the base, to 70 cm in diameter. Stems terete, green, decumbent and prostrate, forming adventitious roots at the nodes, not markedly hollow; new growth glabrous to sparsely pubescent with eglandular simple, uniseriate (3-)4–10-celled spreading trichomes 0.5–2.0 mm long, occasionally with a few glandular trichomes with a 1-many-celled apical gland; older stems glabrescent. Sympodial units difoliate or trifoliate, the leaves not geminate. Leaves simple and shallowly lobed to deeply pinnatifid, (0.5-)2.0–4.0(-5.0) cm long, 0.2–2.9 cm wide, narrowly elliptic to oblong or ovate-elliptic, fleshy in texture, green to dark green; adaxial surface glabrous to sparsely pubescent with simple, uniseriate trichomes like those on stem, scattered along lamina and more densely along the veins; abaxial surface more densely pubescent on veins and lamina; major veins 3–6 pairs, not clearly evident abaxially; base cuneate, decurrent on the petiole; sinuate-lobate to deeply pinnatifid to near-pinnate, with 3–6 linear to triangular pairs of lobes; apex acute; petioles (0.5-)1.0–2.0(-2.4) cm long, pubescent with simple uniseriate trichomes like those of the stems. Inflorescences 1.0–2.0 cm long, internodal, unbranched, with 1–5(–6) flowers clustered near the tips (sub-umbelliform), glabrous to sparsely pubescent with spreading trichomes like those of the stems; peduncle 0.8–3.5 cm long, often with apical leafy “bracteoles” (small, leaf-like structures amongst the pedicels); pedicels 3–12 mm long, 0.4–0.5 mm in diameter at the base and 0.4–0.5 mm in diameter at the apex, straight and spreading, articulated at the base; pedicel scars spaced 0(-0.5) mm apart. Buds narrowly ellipsoid or occasionally narrowly ovoid, the corolla exserted 1/5–2/5 from the calyx tube before anthesis. Flowers 5-merous, all perfect. Calyx tube 1.0–1.5 mm long, conical, the lobes 2.5–3.5(–7.0) mm long, 0.8–1.0(–4.0) mm wide, triangular-oblong with acute apices, densely pubescent with simple, uniseriate eglandular trichomes like those of the stem. Corolla 10–14 mm in diameter, white to lilac with a yellow-green central eye with black-purple coloration at the base, deeply stellate, lobed 1/2–3/4 of the way to the base, the lobes 4.0–5.0 mm long, 1.8–2.2 mm wide, reflexed at anthesis, densely pubescent abaxially with short simple uniseriate eglandular trichomes like those on stems and leaves. Stamens equal; filament tube minute; free portion of the filaments 0.6–1.0 mm long, adaxially sparsely pubescent with tangled simple, uniseriate trichomes; anthers 2.8–3.1(–4) mm long, 0.4–0.5 mm wide, narrowly ellipsoid, pale yellow, poricidal at the tips, the pores lengthening to slits with age and drying. Ovary globose, glabrous; style 2.5–3.5 mm long, densely pubescent with 2–3-celled simple uniseriate trichomes to 1/2 from the base, not exserted beyond the anther cone; stigma capitate, minutely papillate, green in live plants. Fruit a globose berry, 8–10(-20) mm in diameter, dark green at maturity, opaque, the surface of the pericarp usually shiny; fruiting pedicels 12–17 mm long, 0.5–1.0 mm in diameter at the base, 1.0–1.5 mm in diameter at the apex, spaced 0–0.5(–1.0) mm apart, reflexed and becoming woody, dropping with mature fruits, not persistent; fruiting calyx elongating in fruit, but not becoming papery nor covering the entire fruit, the tube 2.5–3.0 mm long, the lobes (4.0-)4.5–5.5(–8.0) mm long and 2.2–3.5 mm wide, strongly reflexed to spreading. Seeds 40–60 per berry, 2.0–2.5 mm long, 1.7–2.0 mm wide, subglobose, yellow, the surfaces minutely pitted, the testal cells pentagonal in outline. Stone cells 13–30, 1.0–1.5 mm in diameter. Chromosome number: 2n=2×=24 (South American populations only, see Särkinen et al. 2018).

(Figure 53) Solanumtriflorum is native to the Americas with a disjunct (amphitropical) distribution between temperate South and North America. In North America it occurs in the United States of America from New Mexico and California north to Canada. The species has been introduced outside its native range in temperate areas of Europe, South Africa and Australia (see Särkinen et al. 2018).

In temperate and boreal regions S.triflorum shows broad ecological lability, growing along road sides, sandy soils, in cultivation, and in salt plains between (0-)700 and 2,900 m elevation.

Canada. Wild tomato (Moss 1983). United States of America. Cut-leaf nightshade (many sources; USDA Plants 2017), Husk tomato (Coombs & Bundy 2456), Three-flowered nightshade (Peck 1941).

Berries eaten in times of food shortages and famine (Acoma, Keres, Laguna peoples); fruit boiled and ground for use in a condiment (Zuni people); decoction of the berries taken for diarrhoea (Blackfoot people), stomach aches (Lakota people), used as lotion for sores on horses (Navajo people); planted with watermelons to make them more prolific and ripen earlier (Keres and Navajo peoples)(Moerman 1998 and references therein).

Least Concern (LC); Solanumtriflorum is weedy and common where it occurs (see Särkinen et al. 2018). For EOO see Table 6.

Solanumtriflorum is a distinctive species with a prostrate habit, fleshy, usually pinnatifid, leaves, and deeply stellate flowers with long, thin anthers. The inflorescences usually have a small bracetole at the apex, and berry size varies from small (ca. 10 mm) to very large (ca. 20 mm), but usually a given plant has either small or large berries. Numerous stone cells are found in the berries, sometimes almost outnumbering seeds, and large berries can have as many as 30 stone cells. Pubescence of S.triflorum is quite variable (e.g., Subils 1983), and some plants have a few glandular trichomes, but for the most part plants from North America are either glabrous or very sparsely pubescent with spreading and often somewhat tangled simple trichomes.

Solanumtriflorum has a classic American Amphitropical Distribution (Gray and Hooker 1880; Raven 1963; AAD sensu Simpson et al. 2017), with populations occuring in North and South America, but not between (see also S.nitidibaccatum). Because of its weedy nature, it is often assumed to be introduced to North America (e.g., https://plants.usda.gov/core/profile?symbol=SOTR), but the amphitropical distribution pattern is found in other Solanaceae native to both regions such as Lycium L. (Levin et al. 2007), and groups of solanums such as the Carolinense (subsection Lathyrocarpum G.Don, Wahlert et al. 2015, as “section”) and Elaeagnifolium (Knapp et al. 2017) clades. Solanumelaeagnifolium Cav. (Elaeagnifolium clade, Knapp et al. 2017) has an almost identical amphitropical distribution (sensu Simpson et al. 2017) AAD, and is similarly weedy; it has also been assumed to be introduced. Distribution of these disjunct groups is more likely to be the result of long distance dispersal than of vicariance (Guilliams et al 2017), with dispersal after being eaten and passed through an animal’s gut (endozoochory) being less common than disperal via attachment to an animal’s fur or feathers (epizoochory) (Schenk and Saunders 2017); soft juicy berries make endozoochory more likely as a distribution mechanism, although there is no information on frugivores or fruit dispersal for S.triflorum. The distribution of S.triflorum in temperate areas, but also at higher elevations in deserts and into the more boreal regions of North America places it in the temperate AAD category of Simpson et al. (2017); annuals like S.triflorum predominate in this category. Amongst temperate AAD species the most common direction for distribution is from North to South America, but we suspect that like Verbenaceae (Frost et al. 2017) and Lycium (Levin et al. 2007), most Solanum disjunctions will have a South America to North America directionality. To date, only North American populations of S.triflorum have been included in molecular phylogenetic studies (Särkinen et al. 2015b).

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

See Suppl. materials 1 and 3.