1	Leaves glabrous beneath or strigillose only on the costa, even when young.
2	Leaves 3.5–10.5 cm long, 0.8–2.5 cm wide	6. Sommera parva
2’	Leaves 7–29 cm long, 1.8–12 cm wide.
3	Calyx lobes 2.5–8 mm long, ovate-lanceolate to oblanceolate	Sommera arborescens p. p.
3’	Calyx lobes 1–2 mm long, semicircular to narrowly triangular	Sommera chiapensis
1’	Leaves pilose-strigillose, strigillose, or sericeous beneath, at least when young.
4	Branchlets glabrous; petioles 4.5–9 cm long; inflorescences 2–4-flowered; pedicels 10–28 mm long; hypanthium and calyx tube glabrous	Sommera cusucoana
4’	Branchlets densely strigillose to sericeous; petioles 0.1–5 cm long; inflorescences 3–25-flowered; pedicels (0)1–10 mm long; hypanthium and calyx tube densely strigillose-villous to sericeous.
5	Mature flowers with calyx lobes 2.5–8 mm long, calyx tube 0.5–1 mm long; pedicels 1–10 mm long; Mexico, Guatemala	Sommera arborescens p.p.
5’	Mature flowers with calyx lobes 1–6 mm long, calyx tube 1–4 mm long; pedicels 0–4 mm long; Guatemala to Panama.
6	Mature flowers with calyx tube 3–4 mm long	Sommera montana
6’	Mature flowers with calyx tube 0.6–2 mm long.
7	Mature flowers with calyx lobes 2.5–6 mm long, calyx tube 1–2 mm; Guatemala	Sommera guatemalensis
7’	Mature flowers with calyx lobes 1–5 mm long, calyx tube 0.6–1 mm; Honduras, Nicaragua, Costa Rica and Panama	Sommera donnell-smithii