Solanum wrightii Benth.

Solanaceae, Jennifer M Edmonds. Oliganthes, Melongena & Monodolichopus, Maria S. Vorontsova & Sandra Knapp. Flora of Tropical East Africa. 2012

Type

Type: China, Hong Kong, Wright 489 (K!, holo.)

Morphology General

Large shrub or small tree to 12 m high with large flat crown; trunk becoming thick, dark brown, girth to 70 cm with smooth pale grey-brown bark, glabrescent; younger stems lanate/pubescent with spreading stalked (to 1.6 mm) stellate hairs mixed with scattered short simple eglandular hairs; shortly-stalked club-glands also present throughout; stems and branches with scattered to dense sharp stout yellow and sometimes recurved acute prickles to 10.5 × 4 mm, sometimes unarmed

Morphology Leaves

Leaves alternate or opposite, often coriaceous, dark green above, yellowish below, ovate to ovate-lanceolate, 11–30(–60) × 6–25(–40) cm, bases usually cordate and distinctly unequal, margins entire, sinuate or deeply sinuate-dentate often on the same plant, with 0–4 acute or obtuse antrorse lobes up to 9 cm deep, apices acute; with scattered small prickles on lower midribs; upper surfaces strigose with simple bulbous-based eglandular hairs to 1 mm mixed with scattered club-glands especially on midrib where mixed with stalked stellate hairs; lower surfaces lanate with long-stalked stellate hairs to 1.25 mm diameter with 4–8 spreading rays with a short central ray; petioles 1.5–7.5 cm long, stellate-strigose; occasional prickles sometimes present

Morphology Reproductive morphology Inflorescences

Inflorescences subterminal to lateral simple and few- to 50-flowered lax, helicoid cymes, with extended rachides in fruit, flowers andromonoecious, 5-merous; axes strigose with eglandular and glandular hairs mixed with long-stalked (–2.5 mm) stellate-hairs and stalked club-glands, becoming woody and glabrescent in fruit; peduncles erect and 1.4–6 cm long in flower and fruit; pedicel erect to recurved and (7–)11–21 mm long in flower, 10–26 mm in fruit

Morphology Reproductive morphology Flowers Calyx

Calyx pale green, campanulate/cupulate, 1.1–1.8 cm long, densely glandular- and stellate-strigose, glabrous internally; lobes narrowly triangular, 9.5–15 × 2–3.5 mm, with membranous margins, subulate-acute and recurved; calyx tube enlarging, becoming thickened and raised in fruit forming a woody rim around the berry base surmounted by adherent triangular calyx lobes

Morphology Reproductive morphology Flowers Corolla

Corolla blue, purple or lilac and fading with age often to white, usually with a contrasting basal star and median veins, stellate, 2.5–4.4 cm radius; tube 1–2 mm long, glabrous; lobes broadly triangular, 1.3–2.8 × 1.1–2.5 cm, acute with dense tufts of small hairs, with dense central bands of small sessile stellate hairs externally, ± glabrous internally except for median veins, corolla reflexed exposing androecium after anthesis

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens usually equal within each flower, occasionally unequal; filaments free for 2–3.5 mm, sometimes thick and tubular, glabrous; anthers yellow to brownish, poricidal, 10–16 × 1.2–2.2 mm long, connivent

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary 1.5–4 × 1.8–3 mm, glabrous, 4-locular; style straight either enclosed at base of staminal tube when 1.5–3 × 0.4–1 mm, or 6.5–18 × 0.7–1 mm and exserted up to 2 mm, white, glabrous but with small stipitate glands especially towards the base, sometimes tubular; stigma green, capitate, 0.3–1.5 mm diameter

Morphology Reproductive morphology Fruits

Berries smooth, yellow to greenish-yellow (? to red), spherical, 4–5 cm diameter, glabrous glossy, leathery with thick pericarp

Morphology Reproductive morphology Seeds

Seeds numerous (> 100), reddish- to dark brown, ovoid, obovoid or orbicular, 2.5–3.3 × 2–2.7 mm, rounded not flattened, deeply reticulate; sclerotic granules absent.

Ecology

Widely cultivated in gardens and arboreta, an escape in riverine and evergreen forest; 800–1700 m

Note

This species was originally described by Bentham (1861) from Hong Kong, but its native country is Bolivia. Bentham did note in his protologue that “no authentically wild specimens have ever been seen in China”. Solanum wrightii is now frequently cultivated as an ornamental tree, largely for its showy flowers, in tropical regions of the world, where it often escapes becoming naturalised; it is commonly known as the “Potato-tree” or the Brazilean Potato Tree. It is also occasionally used for shade in Mexico. Bitter incorrectly united this species with S. grandiflorum Ruiz & Pav. without examining the type of the latter. This is a very different species characterised by a floccose indumentum, absence of prickles and deeply lobed corolla (White in F.F.N.R.: 377, 1962). The considerable confusion surrounding the synonymy of this species was discussed by Heine (1960).  Bentham (1861) originally mentioned that his new species seemed to belong to the Melongena group. Later authors agreed or followed this treatment including Jaeger (1985) & Bukenya & Hall (1988). Bitter (1923) included it in his series Acanthocalyx Bitter; Seithe (in E.J. 81: 330, 1962) tentatively included it in the section Stellatipilum while Whalen (1984) placed it in his Solanum crinitum group, later including it in the section Crinitum (Whalen) Childs (Whalen 1999). Gonçalves (2005) subsequently followed this infrageneric categorisation. The species is reportedly strongly andromonecious with reduced and sterile gynoecia. All herbarium material examined exhibited large anthers and the majority had only short styles embedded within the staminal column, though the ovaries all appeared to bear numerous ovules. Occasional specimens exhibited long exserted styles. Only one or two fruits reportedly develop from each inflorescence, and these have been variously described as yellow or red but no annotations were found on herbarium specimens to clarify its berry colour. Symon (in J. Adelaide Bot. Gard. 8: 158 (1985)) recorded up to 258 seeds in one New Guinean fruit examined, though he followed other authors by identifying it as S. grandiflorum Ruiz & Pav. Solanum wrightii is densely pubescent, exhibiting a mixture of stalked stellate hairs in which the reduced central ray may or may not be glandular; both long and short multicellular simple hairs which can be spreading or appressed and have glandular or eglandular heads, together with scattered stalked club glands. The stalked stellate hairs are often visible to the naked eye with the tubular and striated stalks varying in length up to 2 mm. As with other species, prickles can be present or absent on plants of S. wrightii; when present they are usually found on the stems, petioles and lower midribs. Apart from its widespread ornamental use, this species is cultivated as a nematode resistant rootstock for S. quitoense in Ecuador, Colombia and Florida, with the fruits commonly being used as soap for washing clothes and medicinally for treating tumours (cf. Mansfeld, 2001). Its charcoal has been used as gunpowder when mixed with ‘chora’ in Tanzania ( Kanywa 30).

Distribution

Range: Probably native to the northern Andes of South America, but now widely cultivated throughout the tropics Flora districts: U (cult., U fide Bitter, U 1923); K4 T1 T2 T3 Range: Sierra Leone, Ghana, Nigeria, Cameroon, Gabon, Congo-Kinshasa, Rwanda, Malawi, Zambia and Zimbabwe