Prickly nightshades are troublesome weeds of natural habitats, pastures, feedlots, right-of-ways, and croplands. Native and nonnative invasive weedy species of prickly nightshades were compared to determine growth, development, and morphological differences. Six (Solanum bahamense, Solanum capsicoides, Solanum carolinense, Solanum dimidiatum, Solanum donianum, and Solanum pumilum) of the 18 species of prickly nightshades studied are native to the US. Two species, Solanum citrullifolium and Solanum rostratum, are annuals; the others are perennials or are short lived perennials or annuals in northern extremes of their range in North America. Tables were developed from new and existing data to differentiate vegetative and reproductive characteristics among 18 species of prickly nightshade found in the southeastern US. In greenhouse experiments, average plant height ranged from 24 and 26 cm (9.45 and 10.24 inch) for S. carolinense and Solanum jamaicense, respectively, to 100 and 105 cm for Solanum tampicense and Solanum sisymbriifolium, respectively at 10 wk after emergence (WAE). By 10 WAE, the average number of leaves per plant ranged from < 10 for S. carolinense and Solanum torvum to > 40 leaves/plant for S. rostratum and S. dimidiatum. Average number of nodes/plant main stem ranged from 11, 12, and 14 nodes in S. jamaicense, S. torvum, and S. carolinense, respectively, to 54 nodes in S. rostratum. Average plant dry weights were collected at 10 WAE and were greatest for Solanum mammosum and (> 17 g/plant) (0.6001 oz/plant) and least for S. carolinense (1 g/plant). Based on these data, nightshade growth rate and dry weight were variable among some species and variability may be a result of phenology and life cycles, annual or perennial. Plants of S. rostratum, an annual, were relatively tall and produced high number of nodes and leaves and had the shortest period from emergence to flower among the prickly nightshades evaluated.

Nomenclature: Bahama nightshade, Solanum bahamense L.; buffalobur, Solanum rostratum Dunal SOLCU; eggplant, Solanum melongena L.; fuzzyfruit nightshade, Solanum candidum Lindl.; hairy horsenettle, Solanum pumilum Dunal; Himalayan nightshade, Solanum myriacanthum Dunal; horsenettle, Solanum carolinense L. SOLCA; Jamaican nightshade, Solanum jamaicense P. Mill.; mullein nightshade, Solanum donianum Walp.; nipplefruit nightshade, Solanum mammosum L.; red soda apple, Solanum capsicoides All. SOLCI; robust horsenettle, Solanum dimidiatum Raf. SOLDM; silverleaf nightshade, Solanum elaeagnifolium Cav. SOLEL; sticky nightshade, Solanum sisymbriifolium Lam. SOLSI; tropical soda ap