Herbs 0.2-0.6 m tall, erect. Stems 3-5 mm in diameter at base of plant, dark green, sometimes tinged with purple, unwinged or with wings to 1 mm wide, coarsely pilose with typically whitish non-glandular erect trichomes; tubers typically borne singly at the end of each stolon.
Sympodial units tri- to plurifoliate, not geminate.
Leaves odd-pinnate, the blades 8-15 x 5-15 cm, medium to dark green and sometimes tinged with purple abaxially, membranous to chartaceous, moderately pubescent adaxially and abaxially with hairs like the stems; lateral leaflet pairs 1-4, greatly subequal and rapidly decreasing in size to the base; most distal lateral leaflets 1.5-10 x 0.4-8 cm, narrowly to broadly ovate to more rarely orbicular, the apex typically acute to acuminate to more rarely rounded and apiculate, the base typically sessile and short to widely decurrent on the basiscopic side to more rarely short-petiolulate; terminal leaflet 3-14 x 1-8 cm, narrowly to broadly ovate to more rarely orbicular, the apex typically acute to acuminate to more rarely rounded and apiculate, the base attenuate; interjected leaflets 0-7, sessile to short petiolulate, ovate to orbicular; petioles 0.7-3 cm, coarsely pilose with typically whitish non-glandular erect trichomes. Pseudostipules minute to 12 mm long, lunate, coarsely pilose with typically whitish non-glandular erect trichomes.
Inflorescences 2.5-10 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 5-15 flowers, with all flowers apparently perfect, the axes pubescent with hairs like those of the stem; peduncle 1.3-8 cm long; pedicels 1.5-8 mm long in flower and fruit, spaced 1-10 mm apart, articulated typically in the distal half.
Flowers homostylous, 5-merous. Calyx 6-11 mm long, the tube 1-2 mm, the lobes 3-5 mm, linear to long attenuate, the acumens 2-4 mm long, pubescent with hairs like those of the stem. Corolla 2.8-3.5 cm in diameter, pentagonal to rotate, dark blue to violet and typically with a green central star adaxially and abaxially, the tube 1-2 mm long, the acumens 1-1.5 mm long, the corolla edges flat, not folded dorsally, glabrous abaxially, minutely puberulent adaxially, especially along the midribs, ciliate at the margins, especially at the tips of the corollas. Stamens with the filaments 1-2 mm long; anthers 4-7 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 8-9 mm x ca. 1 mm, exceeding stamens by 2-4 mm, straight, glabrous; stigma clavate to capitate.
Fruit a globose to slightly ovoid berry, ca. 1.5 cm wide, 1.5-1.8 cm long, medium to deep green when ripe, often with scattered white dots, glabrous.
Seeds from living specimens ovoid and ca. 2 mm long, whitish to greenish in fresh condition and drying brownish, with a thick covering of “hair-like” lateral walls of the testal cells that make the seeds mucilaginous when wet, green-white throughout; testal cells honeycomb-shaped when lateral walls removed by enzyme digestion.
Solanum medians is found from central Peru (Dept. Ancash) south to northern Chile in Regions I (Tarapacá) and II (Antofagasta), along the western slopes of the Andes; growing in a variety of sunny habitats along the dry coastal lomas to high frigid areas near snow fields and among Stipa ichu grasses in the puna. The most frequently mentioned habitat characteristics are apparently poor soils in rocky and sandy areas, but it has been collected along field margins and streamsides; 200-3800 m in elevation.