Seed Germination of Garberia heterophylla (W. Bartram) Merr. & F. Harper, a Pollinator Plant with Ornamental Appeal

Seed propagation is the primary means of reproducing many native and endemic species, including garberia [Garberia heterophylla (W. Bartram) Merrill & F. Harper]. This attractive pollinator plant, native to Florida, is scarcely found in nursery production and largely unknown to the gardening community. To better understand the seed biology of garberia, a series of experiments were conducted to evaluate the effects of population on seed viability and germination response to four seasonal temperatures, as well as the effects of time on seed storability. Initial seed viability was 49% and 60% for Central and North Florida populations, respectively. Seeds germinated readily, indicating non-dormancy, with significant effects of population and temperature observed. Overall, on day 28, a greater germination proportion was observed from seeds collected from North Florida than Central Florida across temperatures, except for winter (11/22 °C), where responses were similar. The greatest germination proportion for seeds collected from North Florida was observed at 15/27 °C (fall) and 19/29 °C (spring), whereas the greatest germination from Central Florida was observed at 11/22 °C (winter), with the steepest decline observed at summer temperatures (24/33 °C). Further, it was observed that garberia seeds are intolerant of long-term storage, losing viability as early as 3 months under conventional cold or room temperature storage and decreasing substantially more after 6 months. These findings contribute to the overall understanding of the seed biology of underutilized species such as garberia, key to the development of efficient and reliable propagation systems for our nursery industry.