Effect of pot type and root structure on the establishment ofTilia cordata andUlmus minorplants after transplanting

Tree production in containers has increased in recent years as this nursery technique makes it possible to year round. Conventional smooth-walled containers can result in low-quality root systems if roots become concentrated against the sidewall, poorly utilise most of the soil volume available within the container, girdle within the container wall or grow vertically to the bottom. The aim of this study was to evaluate the effects of different container types used in the nursery industry on root growth and conformation after transplanting. One-year-old plants of littleleaf linden (Tilia cordata Mill.) and field elm (Ulmus minor Mill.) were grown for two years in three different container types (Air-Pot®, Quadro Antispiralizzante and traditional smooth-sided) then planted in the field in spring 2010. In March 2012 half of the plants were harvested to measure shoot and root biomass and to count the number of deformed roots. Chlorophyll fluorescence and leaf chlorophyll content were measured during three growing seasons after planting. Field elm root biomass was significantly reduced in plants cultivated in Air-Pot®. The number of deformed roots after two years from transplant in both of the species tested was considerably less for trees grown in Air-Pot® containers than for specimens propagated in the other pot styles. No differences in linden shoot growth was observed in 2010, though in 2011 and 2012 the largest shoot growth was recorded on plants grown in Air-Pot® containers. Air-Pot® containers appeared to be the most likely to result in a good root system structure after planting.