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.

The spread of buffalobur in China poses a serious threat to existing ecosystems, and control and eradication of this species have become increasingly important. Studies were carried out to ascertain the seed production, morphological characterization, dormancy behavior, and methods for breaking dormancy of buffalobur. The results showed that a single buffalobur plant could produce 1,600 to 43,800 seeds with an average weight of 3.0 mg. Average seed length, width, and thickness were 2.5, 2.0, and 1.0 mm, respectively. Newly ripened buffalobur seeds were innately dormant and exhibited combinational dormancy, which involves a hard seed coat (physical dormancy, PY), a partial dormant embryo (physiological dormancy, PD), and a dark requirement to germinate. PY of buffalobur seeds could be broken by dehusking or acid scarification by 14 M H2SO4 for 15 min, with germination rates of 55 or 50%, respectively. PD was effectively broken by KNO3 or gibberellic acid (GA3). The optimum concentration for KNO3 was between 20 and 40 mM, which resulted in over 70% seed germination. When presoaked with GA3 at 30 C in dark for 24 h, maximum germination (> 98%) was obtained at 2.4 mM, the corresponding germination speed (85%) and germination index (16) were also highest at this concentration. Synergistic effects were observed in seed germination when H2SO4 and GA3 were combined. The most rapid and effective combination in breaking dormancy was when the seeds were immersed in H2SO4 (14 M) for 20 min and presoaked with 2.4 mM GA3 for 24 h. Germination index for this combination was over 35, and 95% of the seeds germinated within 7 d. Knowledge gained in this study will be useful in increasing germination of buffalobur and facilitating further laboratory studies.