Effects of Nursery Container Color and Spacing on Root Zone Temperatures of ‘Soft Touch’ Holly

Newly up-potted ‘Soft Touch’ Japanese hollies (Ilex crenata ‘Soft Touch’) were grown in Mobile, AL in 1.5 L containers to evaluate the effects of growth from black or white container colors and container spacing (jammed or spaced) in relation to root zone temperature. Two treatments, container color and container spacing, were evaluated and root ratings were reported. At termination, an interaction was observed in growth from 43 to 141 days after potting between container color and spacing. Both white container treatments and the black-jammed treatment experienced 36% and 21% more growth than black-spaced plants. Root ratings for white containers (jammed and spaced) were 42% greater than for black-spaced. Black-jammed root ratings were 25% greater than black-spaced. Black-spaced containers experienced the greatest number of time intervals over the critical temperature of 39 °C when compared to other treatments. Results suggest that ‘Soft Touch’ holly may be grown at final spacing when using white containers and have little impact from elevated root zone temperatures.