Field Production Methods for Season Extension of Peony ‘Coral Charm’

Paeonia lactiflora is a high-value crop with a temperature-dependent growth response that requires worldwide production to satisfy year-round demand. The objective of this study was to evaluate production and timing of ‘Coral Charm’ peony as a cool-season crop in the US Intermountain West. High-tunnel and field production were trialed in North Logan, UT, USA (lat. 41.77°N, long. 111.81°W; elevation, 1382 m) with the addition of low tunnels and soil heating methods to advance growth in 2019–21. Soil and air temperatures, as well as the date and quality of harvested stems, were measured. High tunnels yielded 15.7 ± 3.3 to 19.4 ± 2.1 stems/m2 [± standard error (SE)] and the high tunnel alone advanced initial harvest 21 to 34 days earlier than natural field conditions. The field yielded 16.1 ± 1.9 to 20.8 ± 1.6 stems/m2 and staggered production, resulting in a harvest duration up to 38 days across the high tunnel and field. The use of a low tunnel with soil heating advanced the initial harvest date compared with natural (i.e., unmanipulated) high-tunnel and field conditions by 3 and 7 days in 2019, 6 days in 2020, and 16 and 6 days in 2021 in the high tunnel and field, respectively. However, the quality decreased significantly under low tunnels with soil heating within high tunnels, compared with unheated plants, as a result of superoptimal temperatures and humidity that damaged buds and led to an increase in disease and insect pressure. Overall, increasing soil temperature advanced early stages of production when the meristem was below or near the soil surface, whereas increased air temperatures accelerated stem elongation and advanced time to flowering.