What is the climatic range of Chinese tree peonies?

They will grow from the warmest parts of zone 3 to zone 9. In the coldest regions, you can expect less height on a mature plant than one grown in more moderate climate. Additional winter protection of mulch and a wind break will help to protect the plant in zones 3 and 4. In our zone 5 garden, we only mulch the youngest plants. After growing for 4 to 5 years the plants are very hardy and don't require special winter treatment. In the warmer climates, such as southern CA or northern FL, where there is very little chill period or dormancy, it is necessary to force dormancy on the plant by trimming off the green leaves (not the stems) in November. Withhold water and let the plant rest during the months of November and December. By January, it will sprout new leaves and will bloom in early February or March.