United States of America. California: “Nova California”, D. Douglas s.n. (holotype: G-DC [G00144189]; isotypes: BM [BM000838093], K [K001159712]).

Perennial, subwoody herbs or shrubs, erect to ascending, up to 2 m tall. Stems terete, green or purple-tinged, moderately to densely pubescent with simple, uniseriate 4–10-celled spreading eglandular trichomes, 0.5–1 mm long; new growth more densely pubescent. Sympodial units difoliate, not geminate. Leaves simple, 3–10(–17) cm long, 1.3–5(–7.5) cm wide, (broadly) ovate to lanceolate, green or marked with purple, green above, paler greyish-green below; adaxial surface moderately to densely pubescent with simple, uniseriate trichomes like those on stem, these evenly spread along the lamina and veins; abaxial surface more densely pubescent than the abaxial surface; primary veins 4–6 pairs, clearly evident abaxially; base abruptly contracted to attenuate, at times asymmetric, decurrent on the petiole; margins sinuate-dentate to toothed, rarely entire; apex acute; petiole 1–4(–7) cm long, moderately to densely pubescent with simple, uniseriate like those on stem. Inflorescences 1.5–4.5 cm long, lateral, internodal, unbranched to occasionally forked, with (3–)6–14 flowers spaced along the rhachis, moderately to densely pubescent with simple, uniseriate trichomes like those on stems; peduncle 1.5–4 cm long; pedicels 10–41 mm long, 0.3–0.4 mm in diameter at the base and 0.4–0.6 mm in diameter at the apex, straight and spreading, articulated at the base, spaced ca. 0.5–1 mm apart. Buds ovoid and narrower at the tips, the corolla exserted 1/5 of its length beyond the calyx tube. Flowers 5-merous, all perfect. Calyx tube 1–2 mm long, the lobes (1-)1.5–2.9 mm long, 0.7–1.5 mm wide, lanceolate to broadly triangular with obtuse to acute apices, moderately to densely pubescent with simple, uniseriate trichomes like those on stem. Corolla 13–15(–20) mm in diameter, stellate, white to lilac with a yellow-green central eye with black coloration at the base, lobed 1/3 to the base, the lobes 4.5–7 mm long, 2–4 mm wide, strongly reflexed at anthesis, sparsely pubescent abaxially with 1–4-celled simple uniseriate trichomes like those on stems and leaves but shorter. Stamens equal; filament tube 0.3–1 mm long; free portion of the filaments 0.1–0.5(1) mm long, sparsely pubescent with spreading uniseriate 4–6-celled simple trichomes adaxially; anthers (2.5-)3–4.5 mm long, 0.9–1.2 mm wide, ellipsoid and slightly tapered towards the tips, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary globose, glabrous; style 6.5–7.5 mm long, exserted 1.7–2.3 mm beyond the anther cone, densely pubescent with 2–3-celled simple uniseriate trichomes to 1/2–2/3 from the base; stigma capitate, minutely papillate, green in live plants. Fruit a globose berry, 6–14 mm in diameter, black at maturity, opaque, the surface of the pericarp matte; fruiting pedicels 8–11 mm long, 0.4–0.5 mm in diameter at the base, 0.5–0.6 mm in diameter at the apex, spaced 1–3 mm apart, spreading to reflexed, dropping with mature fruits, very occasionally remaining on the inflorescence rhachis; fruiting calyx not accrescent, the tube less than 1 mm long, the lobes 1.2–3 mm long, appressed against the berry. Seeds usually >50 per berry, 1.5–1.9 mm long, 1.2–1.5 mm wide, flattened and tear-drop shaped with a subapical hilum, brown, the surfaces minutely pitted, the testal cells pentagonal in outline. Stone cells (2-)6–8 per berry, rather large, 0.5–0.7 mm in diameter. Chromosome number: 2n=2×=24 (Henderson 1974; Heiser et al. 1965 as S.amethystinum; Edmonds 1982, 1983; Stebbins and Paddock 1949; Heiser 1955 (as S.amethystinum); Soria and Heiser 1961 (as S.amethystinum and S.douglasii).

(Figure 14) Solanumdouglasii occurs in North America from California east to Arizona and south to Nicaragua; it is the most common black nightshade in the southwestern United States of America and northern Mexico.

Open areas and disturbed habitats in a wide variety of vegetation types, from xerophytic to mesophytic forests and oak-pine woodlands between (sea level-) 600 and 3,400 m elevation.

United States of America. Arizona nightshade (Martin and Hutchins 1980), Douglas’ horse-nettle (NatureServe 2017), Douglas’s nightshade (Peck 1941; Martin and Hutchins 1980; Nee 2012), Greenspot nightshade (USDA Plants 2017). Mexico. Hierba (yerba) mora (many sources, [Chihuahua] Chichequelite (Pennington 42), [Chiapas] Moen (Tzeltal, Shilom Ton 9185), Mora wamul (Tzeltal, Gómez López 426), [Guerrero] Moradito (Kruse 1656), [Hidalgo] Tomaquilit (Villa Kumel 53), [México] Tomatillo (la Cruz Bolaños Adec-12), [Oaxaca] Pchfux-yaas (Zapotec, Hunn OAX-1547), Skelemal ch’aben (Tzeltal, López Pérez 326), [Puebla] Teconchichi (Tlapa & Ubierna 105), [Sonora] Chichicalite (Guizar N. et al. 4260).

United States of America. [California] Leaves used as a potherb (Luiseño people of Orange County, Sparkman 1908); juice of berries used as wash for inflamed eyes and in tattooing or for dye (Luiseño people, Sparkman 1908; Cahuilla people of the Sonoran Desert, Bean and Saubel 1972). Mexico. Leaves used as a potherb (“quelite”). See also section on Uses.

Least Concern (LC). Solanumdouglasii is widespread and weedy in the southwestern United States of America and throughout Mexico. For EOO see Table 6.

Solanumdouglasii is most common west of the Rocky Mountains, along the western coast and southwesternmost United States of America along the Mexican border. Solanumdouglasii can be distinguished from the morphologically similar and sympatric S.nigrescens by its longer, slightly tapering anthers (greater than 3 mm long and in North America usually 4–4.5 mm long) and the minute free portion of the filaments. Both species are morphologically highly variable and sympatric through much of Mexico and Central America, often growing in the same areas; detailed studies are needed to establish whether interbreeding occurs between particular areas/populations in areas of sympatry. The two species have been put in synonymy by other authors (e.g., Edmonds 1972; D’Arcy 1974a, b), but characterised as “ill-defined” by others (e.g. Nee 1999).

The description of S.umbelliferumvar.trachycladum cites “Santa Inez and San Buenaventura Ranch” and “Flowers apparently white, about as large as in S.nigrum” (Torrey 1856) with no collector or date. The plants collected in the several expeditions ordered by the United States Government to plan a railway leading across the Rocky Mountains to the Pacific were variously described by Asa Gray (Harvard) and John Torrey (New York). Thomas Antisell collected between the Rio Grande River and southern California; his collections are described in Volume VII of the Reports (Brendel 1880) by Torrey. We have only found a single specimen collected by Antisell and annotated by Torrey with this name; it has the locality “San Buenaventura Ranch/Feb 16/Dr Antisell”. We select this sheet (NY00821411) as the lectotype following McNeill (2014).

In describing S.profundeincisumBitter (1913) cited two collections of Edward Palmer’s from Guadelupe Island, Palmer 60 pro parte and Palmer 61, both from UPS. Palmer 60 is a mixed collection, some parts of which were used to describe S.calvum (a synonym of S.americanum) and some as part of the protologue of S.profundeincisum. The collection Palmer 61 is represented by many duplicates and is not mixed; we select the UPS sheet of Palmer 61 (UPS-V-851402) cited by Bitter (1913) as the lectotype of S.profundeincisum.

See Suppl. materials 1 and 3.