6. Physalis L. (ground cherry, husk tomato)

Plants in our species annual or perennial herbs, sometimes with rhizomes, unarmed. Stems erect or ascending, less commonly loosely ascending from a spreading base, with several to numerous branches, mostly toward the tip, glabrous or hairy. Leaf blades simple, unlobed or with shallow, broad, pinnate lobes, glabrous or hairy. Inflorescences axillary, of solitary flowers (few-flowered clusters elsewhere). Flowers spreading to more commonly nodding. Calyces 0.3–1.6 cm long at flowering, shallowly lobed at the tip, broadly tubular or narrowly to broadly bell-shaped at flowering, rounded to truncate or occasionally slightly concave at the base, lacking basal auricles, persistent at fruiting, the tube becoming enlarged and balloonlike, entirely and loosely enclosing the fruit (this visible only when the calyx is torn apart), 5- or 10-angled to 10-ribbed (then more or less rounded). Corollas 0.6–2.0 cm long, broadly bell-shaped to saucer-shaped, shallowly 5-lobed to nearly entire, usually appearing pleated in bud, light yellow to lemon yellow, often with 5 large, prominent dark purplish brown to dark reddish brown spots on the inner surface toward the base (these sometimes merged into a ring or appearing smudged), rarely white. Stamens with relatively short filaments, the anthers erect, positioned in a loose ring but not fused laterally, dehiscent longitudinally, light yellow to yellow or less commonly purplish blue to dark blue (sometimes only bluish-tinged or -lined). Ovary 2-locular, the style usually protruding through the center of the loose ring of anthers. Fruits berries, more or less juicy, globose, 2-locular, green, yellow, or orange, sometimes purplish-streaked or -mottled, with numerous seeds, lacking stony granules (these present elsewhere). Seeds 1.5–2.5 mm in longest dimension, more or less kidney-shaped to asymmetrically ovate, flattened, the surface minutely pitted, sometimes only faintly so, more or less shiny, light yellow to orangish yellow or light yellowish brown, lacking wings. About 75 species, nearly worldwide.

The species of Physalis are variously known as husk tomato, ground cherry, and tomatillo. The cultivated tomatillo, which is a staple in Mexican cooking and salsas, is P. philadelphica, an annual species native to Mexico and the adjacent southwestern United States. Tomatillos have successfully bridged the gap from an ingredient in a regional cuisine to a more general food source, and usually are available in the produce section of grocery stores year-round. Steyermark (1963) noted that although plants (including immature fruits) of Physalis should be considered toxic to livestock and humans, the mature berries of several of the juicier-fruited Missouri species can be prepared into jams and preserves or eaten raw.

When collecting specimens of Physalis, it is important to note whether the plant is annual or perennial. In annuals, the rootstock generally is easily pulled up with the rest of the plant. The perennials mostly have deepset rhizomes that are collected infrequently. In both cases, the stems generally do not appear colonial. Also, a notation of whether the corollas have dark spots facilitates determination, as the flowers often press in a closed position. Finally, if fruits are present, whether the inflated calyces are sharply 5-angled or bluntly 10-angled is important to note, as this character can be difficult to diagnose in pressed materials. Fertile material, preferably with both flowers and fruits, is necessary to determine some of the taxa with confidence.

The taxonomy and nomenclature of Physalis are complex and there have been numerous changes since the last comprehensive taxonomic treatment of the temperate North American species by Waterfall (1958, 1968). The present work closely follows that of J. R. Sullivan (2004), whose excellent treatment of the species present in the southeastern United States includes most of the Missouri taxa.

Steyermark (1963) discussed the existence of a historical specimen from the Allenton area (St. Louis County) of what he called Physalis lobata Torr. This species is now segregated by most botanists into a separate genus, Quincula Raf. (Barboza, 2000), comprising only the species Q. lobata (Torr.) Raf. Purple ground cherry is native to the southwestern United States (west to Kansas and Texas), as well as northern Mexico. It is similar in general morphology to Physalis, but differs from at least the Missouri species in its small clusters of ascending flowers with purple corollas, its dull seeds with a network of ridges on the surface, and details of its calyx venation and trichome structure. Steyermark (1963) chose to exclude the sole Missouri specimen from the state’s flora in the belief that it was mislabeled and actually collected in another state. Steyermark was personally acquainted with the collector, John Kellogg, and presumably was able to confirm that Kellogg had not collected the species in eastern Missouri. Unfortunately, the specimen in question could not be located during the present study. Thus, Steyermark’s exclusion of the taxon from the Missouri treatment is continued in the present work.