2014 ASHS Annual Conference

Above-ground container nursery production makes up more than 50% of the $26 billion woody plant nursery industry in the United States. Circling and/or malformed roots, a common problem with container-grown plant material, can negatively impact plant health and stability both in the nursery and landscape after transplanting. Roots deflected in plastic containers grow in many directions, including up, down or around the root ball; some roots may “kink” 180 degrees and go back the way they grew from, causing constrictions and circling roots. Research has found that fabric containers have fewer circling/girdling roots compared to those grown in other smooth-sided containers. Long-term survival of trees planted into the landscape may be influenced by the container in which they are grown.  Malformed roots that begin with container production can lead to tree instability and possible failure. Our research, conducted at Colorado State University (Fort Collins, Colo.), examined container effects on Pyrus calleryana ‘Glen’s Form’ (Chanticleer®) establishment for three years following transplanting. The three container types were the industry standard black plastic (BP), and Root Pouch® (RP) and Smart Pot® (SP). Trees were grown in the nursery one season and then planted into the landscape. We found no container effects on above-ground growth (height, caliper, leaf area, leaf and shoot dry weight) in 2011, 2012 and 2013. Container type significantly affected root dry weight, root re-growth and fine root development. Trees grown in BP containers had the greatest root dry weight, yet BP-grown trees had the least amount of root re-growth beyond the original root ball after three years (29%), compared to RP- (35%) and SP-grown (37.3%) trees. There was greater fine root development for the two fabric containers (RP and SP) compared to BP containers. This suggests that three years following planting, container type still directly affects root establishment and development. Our research found that fabric containers resulted in trees with a more natural, lateral branching root system compared to trees grown in BP containers. Further, above-ground growth may not indicate if a tree’s root system has established correctly. Based on our study, if long-term growth and plant health is a priority for growers, tree care professionals and homeowners, then fabric containers should be considered as alternatives to black plastic containers.