Impacts of greenhouse fertilization and planting season on survival and reproductive potential of Silene regia transplants

Restoration of rare plants is essential to maintain species diversity in natural areas. The methods used to grow and plant these rare plants for restoration impact seedling health and potentially the success of restoration attempts. We evaluated how different fertilizers and planting seasons impacted survival and reproductive potential for transplants of Silene regia. Plants were grown from seeds in greenhouses with four fertilizer treatments: slow-release, liquid biweekly (every other week), liquid weekly, and control (no fertilizer). Transplanting was conducted in spring and fall for 2 years (2010 and 2011) at three sites. Number of leaves on transplants were counted before planting. Plants were counted over the growing seasons for 8 years (2010–2017) to determine survival and stem elongation (an indication of reproductive potential). Transplants produced the most leaves with slow-release, followed by both liquid fertilizers and the fewest leaves with no fertilizer. The fertilizer type had a limited effect, but plants grown with fertilizer had increased survival and stem elongation relative to no fertilizer when a fertilizer effect was found. Planting season had a more consistent effect, with spring having higher survival and stem elongation. Sites differed for all measured parameters. Year-to-year survival was initially high, then dropped after 3–5 years, and less than 20% of plants remained by 2017. These findings demonstrate the value of pre-planting fertilizer to provide vigorous transplants and planting season for reintroductions. Finally, multiple sites and long-term monitoring are important to ensure success for reintroductions of rare species such as S. regia.