The 2011 ASHS Annual Conference

The most commonly used container type for nursery tree production is the black plastic (BP) container. Roots of plants grown in BP can be injured by the wide diurnal temperature fluctuations which occur during most of the growing season. The longer trees remain growing in BP, the greater the potential for the development of circling and malformed roots. Root injury sustained during production may negatively affect tree health when planted in the landscape. Our research uses Pyrus calleryana Decene. ‘Glen’s Form’ (Chanticleer®) to compare tree production using two non-conventional, fabric container types (Root Pouch®, Averna & Associates, Hillsboro, OR, and Smart Pot, High Caliper Growing-Root Control, Inc., Oklahoma City, OK) along with BP containers. Our hypothesis is that the use of fabric containers will reduce the severity of root zone temperature fluctuations seen with BP, promote the development of healthier root systems, enhance tree growth rate, shorten production time and produce trees that show less stress and establish more quickly when planted in the landscape. Trees are being grown in a nursery production setting using current industry standards. In addition to container type, two overwintering treatments are being examined – trees are either consolidated pot-to-pot in a block or left “lined out” in rows. Standard tree growth measurements are taken throughout the growing season. A portion of the trees are destructively harvested in the first, second and third seasons following initial planting in containers. Trees are planted into the landscape during the first through third growing seasons; trees will be fully excavated and harvested (after one, two and three growing seasons) to compare transplant root and shoot growth. Post transplant stress of trees will be determined during the growing season using chlorophyll fluorometry, pre-dawn leaf water potential and infrared leaf temperature. In 2010 there were no statistical differences in height, dry leaf weight, dry shoot weight and dry root weight among the three container types. Trees growing in BP had greater caliper than those in the fabric containers. Trees growing in BP had more circling roots than those produced in both fabric container types. Container media temperatures, measured with thermocouples in two locations in each container, also varied by container type. The southwest side of all container types exhibited the widest diurnal temperature fluctuations; however, fluctuations were greatest in BP (as much as 30 °C within a few hours).