Influence of Moisture on Cold Hardiness of Six Container-Grown Herbaceous Perennials
Overwintering container-grown plants is often necessary during production. Plants maintained in pots at growing medium moisture levels above (‘wet’) and below (‘dry’) 10% volumetric water content were exposed to −2, −5, −8, −11, and −14 C (28, 23, 18, 12, 7 F) in January, then returned to a greenhouse kept at 3 to 5 C (37 to 41 F). In June, plants were assessed using a visual rating scale (1 = dead, 3 to 5 = increasing quality) and shoot dry weight of new foliage growth. Quality rating and shoot dry weight of Coreopsis L. ‘Tequila Sunrise’ and Carex morrowii Boott. ‘Ice Dance’ were not affected by moisture level. Quality ratings were higher for Geranium × cantabrigiense L. ‘Cambridge’ ‘wet’ plants than for ‘dry’ plants and for Heuchera L. ‘Plum Pudding’ ‘dry’ plants than for ‘wet’ plants. Shoot dry weight was higher for ‘dry’ plants of Carex laxiculmis Schwein. ‘Hobb’ (Bunny Blue™) and Carex oshimensis L. ‘Evergold’ exposed to most temperatures. Of the cultivars studied, effects of moisture level on overwintering container-grown plant growth and quality are cultivar-specific and a universal effect could not be established.