The federally endangered Schweinitz's sunflower (Helianthus schweinitzii) is endemic to the Carolina Piedmont. This study investigates the reproductive biology of this sunflower to better understand the two main methods of propagation: sexual reproduction by seed and asexual reproduction by tuberous rhizome. The researchers randomly collected the mature and senescent heads (capitula) and recorded the numbers of filled and unfilled cypselae in the fall of 2012. Analyses of the effect of the use of gibberellic acids (GA) and the use of a mix of charred soil and aboveground organic matter on seed germination were conducted. The GA treatment at 1,000 mg L−1 significantly increased germination. Cypselae planted in a mix of soil and aboveground matter that had been burned for 30 min germinated significantly better compared to a control group. To study asexual reproduction, tuberous rhizomes were collected and the effect of a cold treatment was tested as a second part of this study. No shoots formed on the untreated tuberous rhizomes, whereas 100% of the cold-treated tuberous rhizomes formed new shoots; furthermore, shoot length was significantly greater for rhizomes chilled for 60 d compared to rhizomes chilled for 30 d. Both methods of reproduction are important to consider in efforts to restore this endangered species.
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Vol. 80 • No. 1