Shrubs or small trees, to 4 m tall, unarmed. Trunks to 12 cm in diameter; bark of older stems pale brown; young branches strongly sulcate, grayish to reddish, softly tomentose-pubescent, the indument persistent, becoming matted, the hairs short- to rather long-stalked, porrect-stellate, multangulate, dendritic-multangulate, and dendritic-echinoid, nearly furfuraceous.
Sympodial units plurifoliate, axillary leaves lacking.
Leaves simple, the blades 14-32 x 4.2-12 cm, ca. 2.5 times as long as wide, ovate to ovate-elliptic, coriaceous, dark green, velutinous to glabrate adaxially, the hairs touching or lacking, short-stalked, porrect-stellate, whitish tomentose-pubescent abaxially, the hairs stalked, porrect-stellate; unarmed; main lateral veins 10-15 on each side of midrib; bases acute, obtuse, or cuneate; margins entire, occasionally appearing slightly crisped (wavy) in herbarium specimens; apex acute or attenuate; petioles 1-5 cm, ca. 1/14-1/6 the length of the blades, tomentose-pubescent, the hairs mixed sessile and stalked, porrect-stellate, multangulate, and dendritic-multangulate, nearly furfuraceous.
Inflorescences 7-16 cm, pseudo-terminal, many times branched, with ca. 80-240 flowers, the axes unarmed, softly tomentose-pubescent, the hairs mixed sessile and stalked, porrect-stellate, multangulate, and dendritic-multangulate; peduncle (6.1-) 9.8-15.4 x 0.2-0.5 cm, sulcate; rachis 0.6-2.2 (-6.1) cm; pedicels 1.5-3 mm in flower, 4.5-5.5 mm in fruit, closely spaced 0.8-2.8 (-4.4) mm apart, articulated at the base.
Buds 6-8 mm long at anthesis, oblong; corolla tomentose-pubescent in bud, the hairs mixed sessile and short-stalked, porrect-stellate, thin-walled, transparent; calyx lobe sutures obscured by tomentum. Flowers all apparently perfect; calyx subcampanulate, 3.6-5.7 mm long, the tube 2.2-3.3 mm, lobed 1/2-2/3 way to the base, the lobes often splitting unevenly, 1.1-4 x 1.5-3 mm in flower, acute, obtuse or semi-ovate, chartaceous, somewhat translucent, tomentose-pubescent abaxially, the hairs sessile and short-stalked, porrect-stellate and multangulate, a few minute simple and porrect-stellate hairs adaxially on upper fourth of lobes; fruiting calyx accrescent, enveloping but not completely covering the fruit, pubescence as in flower, the lobes 2.9-6 x 5-6.5 mm. Corolla 1-2.2 (-3.1) cm in diameter, 8-14 mm long, soon exserted from calyx, nearly the length of calyx or its lobes by anthesis, stellate, chartaceous, white, the tube 2.3-3.8 mm, the lobes 6-10 x 2.7-4 (-5.5) mm, ovate to ovate-lanceolate, pubescence as in bud abaxially, with few simple and porrect-stellate hairs on upper fourth adaxially. Stamens with filaments 0.9-2 mm, inserted on corolla tube 0.9-1.9 mm above base, glabrous; anthers 3-4.6 x 0.8-1.5 mm, lanceolate, blunt-tipped, golden yellow, free, poricidal at the tips, the pores directed distally and somewhat adaxially, farinose around edges, lengthening to longitudinal slits with age. Ovary subconical to subglobose, tomentose-pubescent, the hairs porrect-stellate and multangulate; style 5.3-6.4 x 0.2-0.3 mm, exserted from stamens, cylindrical, densely pubescent on lower 2/3-3/4, the hairs porrect-stellate and multangulate; stigma capitate.
Fruit a fleshy berry, 0.8-1.2 cm in diameter, globose, obtuse at apex, green, sparsely pubescent, the hairs sessile and short-stalked, porrect-stellate and multangulate.
Seeds 3.1-3.8 x 2.5-3 mm, suborbicular, yellowish-tan, the surface reticulate-punctate.
Solanum bullatum occurs along the southern Brazilian coastal plain, in the highlands of the Serra da Mantiqueira and Serra do Mar ranges and upper drainage basin of the Rio Paraná, Solanum bullatum is a plant of forest margins and thickets from 300 to 1000 m. In semi-desert vegetation it is associated with Araucaria sp.