Tropical soda apple, also known by the common names: joá-bravo, arrebenta-cavalo (in Brazil), ‘tutia de víbora’ (in Argentina), chichihua, uña de gato (in Nicaragua) belongs to the same family as potato, tomato, tobacco, eggplant, and pepper (Solanaceae known as the nightshade family). This dicotyledonous family include about 90 genera and approximately 2000 plant species mainly in the tropics and subtropics of the world (Bailey and Bailey 1976, Long and Lakela 1971). The genus Solanum has a worldwide distribution including the well-known cultivated Solanum tuberosum (potato), and Solanum melongena (eggplant), many weedy species, and several important species that may play a key role in plant community successions, and as a food source of wildlife. Kartesz (1994) on his list of flora of the United States, Canada, and Greenland includes 35 genera with 76 species in the genus Solanum, most of them non-native and introduced from the tropics. Schilling (1981) reviewed the systematic of Solanum sect. Solanum in North America and included 11 weedy species in this group. He indicated that Solanum americanum, Solanum douglasii, Solanum interius, Solanum pseudogracile, Solanum ptycanthum (diploid),Solanum furcatum, Solanum nigrum, Solanum villosum, Solanum scabrum, and Solanum retroflexum (polyploid) are apparently native. Probably, the most complete list of species of Solanum in North America is provided by the USDA Native Plant Database. This list includes about 52 native species of Solanum in North America. There is one Solanaceous species (Solanum donianum) in the list of Florida’s endangered and threatened plants (Coile 1998), and six species (Solanum drymophilum, and Goetzea elegans in Puerto Rico; Solanum incompletum, Solanum sadwicense, Nothocestrum breviflorum, and Nothocestrum peltatum in Hawaii) in the U.S. Fish & Wildlife Service’s list of endangered and threatened wildlife and plants (1997). The genus, includes more than 1,000 species worldwide (Nee 1991). Solanum viarum, subgenus Leptostemonum (prickly Solanum), belongs to the section Acanthophora that includes 19 species (Nee 1991) with prickly stems and dented or lobed prickly leaves. Synonyms that have been used in the past are Solanum khasianum, Solanum chloranthum, and Solanum viridiflorum but the currently accepted name is Solanum viarum.
How this plant was introduced into Florida probably in the 1980's is not known and is currently spreading rapidly forming moderate to dense stands mainly in grassland areas, with short grasses like bahiagrass, Paspalum notatum and in shaded woody areas (oak hammocks). S. viarum plants have a great reproductive potential (100-160 fruits/plant, 41,000-50,000 seeds/plant) and can produce yellow fruits in approximately 4-months. Wild animals as indicated earlier are major vectors for seed dispersion to un-infested areas. Cattle in Florida has been also implicated as major S. viarum disseminator by feeding on ripe fruits with seeds that go undigested through the digestive tract (Mullahey et al., 1996).
