Scientists at North Carolina State University conducted research into storage temperatures of peonies as cut flowers using three temperatures: -3.1C, 0.7C and 3.5C (26.4, 33.2 and 38.3F) in one experiment and -0.6C (30.9F) in another. Cut flowers were harvested mostly in stage 2 but some in earlier stages of opening. They were wrapped in newspaper and placed in boxes that were lined with a polyvinyl wrap and kept in cold storage for up to 14 weeks. Their experiment showed that tolerance to cold temperatures is cultivar dependent and lowering the temperature to 0.7 C 33.2F) and even -.6C (30.9) can extend the storage life without sacrificing (or increasing) vase life. As with a lot of other trials, pulsing with a sucrose solution did nothing for peony vase life.
It is interesting to compare these trials with ones held in Alaska where vase life can be much longer (7-10 days). I have seen a lot of peonies stored for 2 months or more, and the flower quality simply does not compare to flowers held for 4 weeks or less (34F, 1.1C) We also showed that for at least the first two weeks, chilling extended the vase life of peonies. The big issue, however, is translating it into the practicalities of commercial storage. Most storage facilities in Alaska, for instance, would experience refrigeration problems, freeze up, at these very cold temperatures. Retrofitting facilities to work at these low temperatures would be expensive. It most likely would require a facility dedicated to very low cold storage, something like a CA storage facility that was filled with flowers once, kept at a steady at freezing temperatures, monitored religiously to make sure temps didn’t dip suddenly, then opened up 14 weeks later.
For many years the minimum temperature for peony flower death has been -1.6C (29F). This study has not pushed the boundaries beyond those known limits.
Jahnke, N. J. M. Dole, Ben A. Bergmann, Guoying Ma and P. Perkins-Veazie. 2020. Extending cut Paeonia lactiflora Pall. storage duration using sub-zero storage temperatures. Agronomy. 10(11):1694. https://www.mdpi.com/2073-4395/10/11/1694
Abstract: Cut peonies (Paeonia lactiflora Pall.) have a relatively short vase life and limited availability due to seasonal production. Cultivars Festiva Maxima (FM), Monsieur Jules Elie (MJE), and Sarah Bernhardt (SB) stored at 0.7 C had a longer flower open time at 12 weeks of storage compared to those held at 3.1 or 3.5 C, while the flower bud time was unaffected. The flower open time of FM and MJE was no different for stems stored at a sub-zero temperature of 0.6 C for 16 weeks compared to non-stored stems. Flower quality, opening, and lack of deformity was reduced at 16 weeks of storage in comparison to non-stored flowers, but higher for stems stored at 0.6 C compared to 0.7 C. Pre-treating stems before storage with pulses of a commercial hydrator solution or a 200 gL1 sucrose solution for 2 h at 4 C had little commercial significance compared to non-pulsed control stems. The total phenolic content, malondialdehyde, and superoxide dismutase were not effective indicators of open time or quality loss. This study is the first to demonstrate the successful use of a non-freezing, sub-zero storage temperature for peony, and the first to store cut peonies for 16 weeks, despite an increased risk of reduced flower quality.