Postharvest Chilling and Vase Life of Herbaceous Peonies

‘Sarah Bernhardt’ and ‘Duchess de Nemours’ peonies (Paeonia lactiflora) were grown since 2001 at the University of Alaska Fairbanks Georgeson Botanical Garden. Cut stems were harvested on 5-7 July, 2013 and a random sample of each cultivar, 5 single-stem reps per cultivar, were placed immediately into 8 chilling treatments: 0 to 168 hours at 24-hour intervals. Stems were wrapped in newspaper and stored dry, in the dark at 1.9 + 1.0^oC and 85 + 6.6% relative humidity. Immediately following treatment, stems were re-cut and placed in tap water-filled, clean jars  (20.8 + 1.6^oC, 56.2 + 3.2 % relative humidity), under a combination of natural window light and 24-hour fluorescent room fixtures). Dates were recorded daily for full bloom (guard petals at 90^o to the stem) and petal wilt/abscission. In a second experiment, 73 cultivars of herbaceous and Intersectional peonies were stored under the same chilling conditions for one week and evaluated for vase life differences among cultivars and peony classes. Total vase life of ‘Duchess de Nemours’ increased linearly from 6.9 + 1.7 days with no chilling to 13.0 + 0.7 days with 168 hours of chilling. ‘Sarah Bernhardt showed the same trend from 8.2 + 0.9 days (control) to 14.2 + 1.2 days with 168 hours. Both cultivars showed the same rate of increase, but ‘Sarah Bernhardt’ had a greater total vase life at all chilling treatments than ‘Duchess de Nemours’. The greatest increase in vase life occurred between bud stage and full bloom. From full bloom to petal fall, vase life averaged 3.0 + 0.7 days for ‘Duchess de Nemours’ regardless of chilling hours. ‘Sarah Bernhardt’ vase life averaged 4.2 + 0.7 days from full bloom to 120 hours chilling after which vase life decreased.  A minimum chilling period of 96 hours is recommended for ‘Duchess de Nemours’, and 120 hours for ‘Sarah Bernhardt’ for optimum vase life.  Vase life for 73 peony cultivars ranged from 4.3 days to 17.5 days.  Average vase life was similar for Japanese, semi-double and double peonies (9.2 + 0.5 days) whereas the Intersectional (ITOH) hybrids averaged 5.2 + 0.1 days. Only five of the 73 cultivars met USDA No 1 grading standards for stem length as well as the AAA Extra fancy Alaska Peony Growers Association standards for bud diameter: ‘Madame Emilie Debantene’, ‘Mary Brand’, ‘President Taft’, ‘Ruth Cobbs’ and ‘Sarah Bernhardt’.