Plants evolved with roots in the soil, providing a temperature buffer to the root zone most of the year. However, as the nursery industry has primarily moved plants out of the ground and into thin plastic containers with very coarse organic substrates, we are faced with added challenges of managing substrate temperature to ensure healthy plant production. Moreover, resource efficiency, particularly regarding mineral nutrients, is a critical factor in the long-term success of the nursery industry. Fertilizer release is controlled by water and temperature in container-grown ornamental nursery production systems. Thus, it was hypothesized that pragmatic management of substrate temperature and moisture could extend the longevity of controlled-release fertilizer in a container system. This study was conducted to determine the effect of irrigation scheduling, container color, and stratified substrates on substrate temperature management, crop health and development, and fertilizer longevity. ‘Limelight’ Hydrangea (Hydrangea paniculata) were grown in either black or white containers and subjected to a single daily irrigation or the same volume applied in three increments throughout the day (cyclic). Hydrangeas grown in white containers with cyclic irrigation increased plant growth by up to 50% compared to those grown in black containers with single-application irrigation, and stratified substrates reduced phosphorus leaching by 30%. Across all treatments, plant health, root development and fertilizer efficiency were improved with substrate temperature management strategies. The results indicate growers should pursue root zone temperature mitigation strategies to enhance crop growth and salability, increase fertilizer use and efficiency, and decrease phosphorus leaching from nursery containers.
