Madagascar. Antsiranana: pentes orientales du massif de Marojejy (Nord-Est) à l’Ouest de la rivière Manantenina, affluent de la Lokoho, 1500 m, 24 Mar 1949, H. Humbert 23653 (holotype: P [P00352290]; isotype: MO [MO-3707383], K [K000414176]).

Shrub (Ravelonarivo & Rabesonina 636) or slender liana to 8 m in forest canopy. Stems flexuous, ribbed, variably pubescent with simple uniseriate trichomes 0.7–2 mm long, these appressed or spreading, often concentrated around the leaf bases, glabrescent; new growth glabrous or pubescent with simple uniseriate trichomes to 1 mm long. Bark of older stems longitudinally ridged when dry, dark orange to dark red, glabrescent. Sympodial units plurifoliate, the leaves not geminate, evenly distributed along young branches. Leaves simple, 5–10 cm long 1.8–2.5 cm wide, oblong to obovate, thick-chartaceous, sometimes shiny, weakly to strongly discolorous, glabrous on both surfaces or sparsely pubescent in the basal part with simple uniseriate trichomes along the margins; major veins 4–12 pairs, spreading at 45–60° to the midvein and forming loops, the finer venation not visible, or if visible seen as a delicate network; base equal or slightly oblique, short-attenuate; margins entire; apex acuminate to caudate; petiole 0.6–1.2 cm long, canaliculate, pubescent with simple uniseriate 4–8-celled trichomes 0.5–1.5 mm long, these denser along the margins, not apparently twining. Inflorescences terminal at the apex of long slender main branches, 5–12 cm long, furcate or branched, with 3–7 flowers; peduncle 1–7 cm long glabrous, or basal part of peduncle rarely pubescent with simple uniseriate trichomes like those on the stem; pedicels 1.2–2 cm long, apically dilated, glabrous, articulated 0–0.5 mm from base, often leaving a prominent small peg on the rachis; pedicel scars irregularly spaced 0.2–2 cm apart. Buds ellipsoid, the corolla soon exserted from the calyx tube before anthesis. Flowers 5-merous, apparently all perfect. Calyx 1–2 mm long, an open cup, the lobes ca. 1 mm long, ca. 1.5 mm wide at base, broadly deltate to almost absent, unusually to 2 mm long and linear (Birkinshaw 2181), usually rounded to cuspidate at the tips, glabrous with a few simple papillae at the tips, the margins thickened and white in dry material. Corolla 1.2–2.2 cm in diameter, violet, stellate, lobed almost to base, the lobes ovate, 7–12 mm long, 4–5 mm wide, largely glabrous on both surfaces, with minute simple trichomes along and around the margins adaxially. Stamens equal; filament tube 0.5–1 mm; free portion of the filaments 1.5–2 mm long, glabrous; anthers 3–4 mm long, ca. 1.5 mm wide, ellipsoid, not connivent, smooth abaxially, poricidal at the tips, the pores much smaller than anther apices, ca. 0.3 mm in diameter, clearly delineated and not lengthening with age. Ovary conical, glabrous; style 6–9 mm long, protruding 2–4 mm beyond the anthers, straight or curved, glabrous; stigma capitate, the surface finely papillose. Fruit a globose berry, ca. 9 mm in diameter (immature?), green, mature colour not known, the pericarp thin, collapsing on drying to reveal the outline of the seeds, glabrous; fruiting pedicels ca. 2 cm long, ca. 0.6 mm diameter at base, pendulous; fruiting calyx slightly accrescent, the lobes spreading and somewhat reflexed. Seeds 4–8(-10) per berry, 3–4 mm long, ca. 2.5 mm wide, flattened reniform, dull orange-yellow; the surface deeply pitted, the testal cells sinuate in outline.

(Figure 29). Endemic to northeastern Madagascar in the area around the mountain of Marojejy, Antsiranana and Mahajanga provinces.

Wet montane forests, often growing as a epiphyte in cloud forests; 500 to 1500 m elevation.

Madagascar. Antsiranana: liaña vato (Miller & Lowry 4072).

(IUCN 2014). Vulnerable (VU B1a, biii). EOO 12,121 km² (VU), AOO 28 km² (EN). Solanum trichopetiolatum is a species of wet forests, and these are shrinking in extent due to habitat alteration. It does, however, occur in protected areas (e.g., the Marojejy Reserve). In common with other members of the ANS clade in Madagascar, the paucity of collections, indicative of local rarity, coupled with the ongoing habitat threats in Madagascar, indicate monitoring and further collection to assess local rarity are priorities.

Solanum trichopetiolatum is a slender liana endemic to northern Madagascar, with obovate leaves and pale violet flowers. The species is characterised primarily by its unusual pubescence of straight or curved simple 4-8-celled appressed or spreading trichomes 0.5-1.5 mm long on the petioles and sometimes on the young stems. Solanum trichopetiolatum is the only one of the several species morphologically similar to Solanum madagascariense described by D’Arcy and Rakotozafy (1994) that we consider distinct enough to merit species status. In addition to the indumentum described above, Solanum trichopetiolatum can be distinguished from the widespread Solanum madagascariense by its slender, loose inflorescences (Fig. 28) with usually fewer than 10 flowers (versus denser more robust inflorescences with more than 10 flowers), glabrous (versus glabrous to densely pubescent) corolla, and leaves that are more obovate and discolorous on herbarium specimens than is typical of Solanum madagascariense. Solanum trichopetiolatum differs from Solanum humblotii in its possession of a branched inflorescence with usually more than 10 flowers, rather than a few-flowered, unbranched inflorescence. It can also usually be distinguished by its calyx that is not lobed or has minute lobes to only 1 mm long (versus calyx lobes 3-4.5 mm long), but Birkinshaw 1281 from 2500 m elevation in Mahajanga has the distinctive trichomes of Solanum trichopetiolatum but has unusual filiform calyx lobes ca. 2 mm long. Although the plate of Solanum trichopetiolatum in D’Arcy and Rakotozafy (1994) illustrates what appears to be a papillate anther, the protologue describes the anthers as smooth; all specimens we have seen have smooth, rather than papillate anthers. We have removed this part of the original illustration of D’Arcy and Rakotozafy (1994) in our Fig. 28.

The part of Antsiranana surrounding the mountain of Marojejy has been identified by D’Arcy (1992) as an area of high diversity for wet forest Solanum. The overall aspect of Solanum trichopetiolatum on herbarium sheets is highly reminiscent of those specimens considered by D’Arcy and Rakotozafy (1994) to belong to Solanum marojejy (here recognised as belonging to Solanum madagascariense), and leaves of the two species dry a similar dark golden-brown colour on herbarium sheets; the long trichomes and slender inflorescences of Solanum trichopetiolatum allow easy identification. Field and population studies are necessary to further understand the relationship between Solanum trichopetiolatum and Solanum madagascariense.

Madagascar. Antsiranana: Ambilobe, Marojenty, contreforts occidentaux du massif de Marojejy (Nord-Est) près du col de Doanyanala (limite des bassins de la Lokoho et de l’Andraronga), 1949, Humbert 23075 (P); Reserve Naturelle de Marojejy, along the trail to the summit of Marojejy Est, NW of Mandena., 14 Feb 1989, Miller & Lowry 4072 (MO, TAN); Antsiranana Rural, Antsiranana Reserve nationale n. 12-Marojejy; sentier qui mène au 3r camp, au dessus du village de Manentenina, 27 Mar 1990, Randrianasolo 107 (MO, P, TAN); Réserve naturelle intégrale 12, Marojejy, au nord d’Andapa, aux environs du sommet de l’Est, 21 Jan 1994, Rasoavimbahoaka et al. 8 (K, MO, P, TAN); Préfecture d’Antalaha, Sous-Préfecture d’Andapa, commune rurale de Bealampona, Quartier de Befingotra. Sud-Ouest d’Andapa, Réserve Spéciale Anjanaharibe-Sud, village de Mandritsarahely, suivant la rivière de Andranomenabe de la route nationale approchant la chaîne d’Anjanaharibe-Sud, 14 Feb 1995, Ravelonarivo & Rabesonina 636 (MO, TAN); Sous-Préfecture d’Andapa, Commune rurale d’Ambodimanga I, Quartier d’Andilandrano, environ de Hiakan’ny Zamandrabosy, 6 km à l’ouest d’Andilandrano, dans la réserve d’Anjanaharibe-Sud, 4 May 1995, Ravelonarivo & Rabesonina 792 (MO, P, TAN). Mahajanga: ruisseau d’Andasinananatsomanga Amparihy, commune rurale de Matsoandakana, 24 Feb 2008, Bernard et al. 891 (MO, TAN); Tsaratanana Massif, ridge 2 km N of Mahatsabory-Mica, 23 Feb 2003, Birkinshaw 1281 (G, MO).