2018 ASHS Annual Conference

Herbaceous peony (Paeonia lactiflora Pall.) is a popular landscape plant in temperate regions because of its great ornamental value. Peony needs a chilling period to break dormancy and enhance flowering. The objective of this study was to evaluate gibberellic acid (GA₃) effects on replacing chilling requirement and increasing the number of flowering shoots of plants held under different controlled chilling durations. Two peony cultivars, ‘Sarah Bernhardt’ and ‘Inspecteur Lavergne’, from 3-5 eye crowns from Holland, were potted in 1.7-L pots. Plants were placed in a 5°C cooler for 6 weeks in a preliminary study, and 3, 4 or 5 weeks in a follow up study. GA₃ (Florgib, Fine Americas) was applied as a 0 or 100 mg/L drench (250 ml/pot) after moving plants from cooler to greenhouse. For the preliminary study of peonies chilled for 6 weeks, GA₃ did not shorten days to emergence (13 days for both with and without GA₃), but increased the number of shoots on both cultivars (3.7 shoots/pot without GA₃ to 4.9 shoots/pot with GA₃ drench in ‘Inspecteur Lavergne’, and 3.6 shoots/pot without GA₃ to 5.0 shoots/pot with GA₃ in ‘Sarah Bernhardt’) and the number of flowering shoots in ‘Inspecteur Lavergne’. For the follow up study with 3, 4 or 5 weeks of chilling, GA₃ decreased the number of days to emergence (14 days without GA₃ to 10 days with GA₃ in ‘Sarah Bernhardt’, and 19 days without GA₃ to 14 days with GA₃ in ‘Inspecteur Lavergne’) while duration of chilling had no effect, and there was no interaction between GA₃ and duration of chilling. Neither GA₃ nor chilling duration affected the number of days to bud opening. The growth and flowering data are still being collected.