Improving Nursery Production by Reducing Root Zone Temperatures

Abstract

The greenhouse and nursery industry in Alabama is a $294 million dollar industry that continues to grow and economically impacts each of the 67 counties in the state. Many challenges present themselves while growing containerized plants in the Southeastern United States, including heat stress, inadequate or excess moisture, and increased disease pressure. These challenges lead to reduced performance, poor plant health and plant decline. Many of the issues can be linked, directly or indirectly, to the intense heat that can be experienced by containerized plants during the optimal growing season in the Southeastern United States. The intent of this study was to identify easily implemented and economically feasible production techniques that can lower rootzone temperatures. By decreasing root zone temperatures, production can be increased, and labor inputs lowered by use of alternatively colored containers. The potential effects of root zone temperature on controlled release fertilizer were also evaluated along with the effects of reduced root zone temperatures on roots and overall growth of two commonly grown species of plants: ‘Soft Touch’ hollies and garden mums. Black containers were exposed to temperatures over 38°C an average of 55% more than white containers. Plants grown in white containers had 55% better root coverage ratings than those grown in black containers and had increased biomass and growth index measurements.