Evaluation of Methods for Flowering Advancement of Herbaceous Peonies

Experiments to advance early production of herbaceous peony ( Paeonia lactiflora Pall.) flowers were conducted over 8 years in the higher elevation, cooler regions of Israel. Anatomical studies during the summer revealed that flower bud initiation of apical buds in the crowns began at the end of July and continued also in lateral buds from mid-August until the plants became dormant in mid-November. Container-grown plants of various cultivars were moved to cold rooms maintained for 10 to 13 weeks at 2 °C, from mid-August to mid-October, then drenched with 250 mL of various concentrations of GA 3 and transferred to a greenhouse. The optimal GA 3 concentration for flower production was 100 mg·L -1 . Plants treated in this way flowered 2-3 months before the natural flowering period. Field-grown plants in uncovered greenhouse structures were exposed to natural winter cold temperatures (0-10 °C), until they had received various chill units according to a “dynamic model” (for details see Erez et al., 1988). The crowns were then drenched with various amounts and concentrations of GA 3 , and the greenhouses were covered with plastic sheets. The optimal chill units for most cultivars was 40 and the optimal GA 3 drench treatment was 250 mL of 100 mg·L -1 . Covered and GA 3 -treated field-grown plants flowered ≈1 month earlier than untreated plants grown in the open field. The GA 3 treatment also greatly increased the number of produced flowers.