The berry in some species resembles a miniature tomato (and, unlike many species of Solanaceae, is similarly non-poisonous); it is, however, completely surrounded by the enlarged calyx. The species are not always easy to tell apart, and there is not full agreement on species boundaries. Ordinarily, determining whether a plant is annual or perennial is a difficult key character, especially when only herbarium material is available, but in Physalis that character can be particularly helpful and often relatively easy to use. The annual species have a small root, easily pulled from the ground and hence usually present on collected specimens; the perennial species have a large root or rhizome that are often not gathered, the stem ending abruptly.

1. Corolla whitish, with distinct lobes and sinuses; calyx at maturity bright red or orange, over 3.5 cm long.

P. alkekengi

1. Corolla yellow (brown-centered), without distinct sinuses, only minute lobes; calyx at maturity green (or pale orange), less than 3.5 (-3.8) cm long.

2. Stems essentially glabrous or with a few antrorse hairs (especially toward summit); anthers blue.

3. Pedicels 1-3 cm long; perennial.

P. longifolia

3. Pedicels, even in fruit, less than 1 cm long; annual.

P. philadelphica

2. Stems rather evenly spreading-hairy or with at least short retrorse hairs; anthers blue or yellow.

4. Hairs (or little bristles) of stem at least in large part retrorse or recurved, none of them glandular or sticky; anthers yellow, 1.6-2.5 (-2.8) mm long.

P. virginiana

4. Hairs of stem ± dense and multicellular, all spreading, usually at least some sticky or glandular; anthers various.

5. Plants perennial; flowers (10-) 12-18 (-20) mm long; anthers yellow or tinged with blue, (2.5-) 2.8-4 mm long, on broadly widened filaments; mature fruiting calyces ca. 2.5-3.7 cm long, on pedicels ca. 1.5-2.7 (-4.5) cm long.

P. heterophylla

5. Plants annual; flowers 6-9 (-11) mm long; anthers blue, ca. 1.5-2 mm long, mostly on slender filaments; mature fruiting calyces not over 2.5 (-3) cm long, on pedicels less than 1 cm long.

P. grisea