Post-transplant Establishment and Economic Value of Three Tree Species from Five Container Sizes

Abstract

With container-grown trees offered to the public in an increasing array of sizes, it is important to determine the effects of transplant on different size container stock. Transplant shock is a condition of physiological stress, which is a normal consequence of transplanting plants into conditions less favorable than those in the nursery. Clonal replicates of Vitex agnus-castus L., Acer rubrum L. var. drummondii (Hook. & Arn. ex Nutt.) Sarg., and Taxodium distichum (L.) Rich. were grown under common conditions in each of five container sizes #1, 3, 7, 25, or 45 (3.5, 11.7, 23.3 97.8, or 175.0 L, respectively) to minimize residual differences during production. Beginning June 2013, six trees of each container size and species were transplanted to a sandy clay loam field in College Station, Texas. To determine the extent of transplant shock, physiological stress was assessed through xylem water potentials and photosynthetic gas exchange rates. Changes in shoot growth of each tree were calculated along with root growth for two growing seasons. Utilizing industry standards, the initial costs of materials and labor were then compared with the size of trees two years post-transplant to determine return on investment for each container size.

Responses observed in A. rubrum and V. agnus-castus indicted growth increased exponentially in #3 and #7 container-grown trees. Taxodium distichum recovered at much slower rates, with less rapid although still vigorous growth in #3 and #7 container-grown trees. Data indicates all trees in #3 and #7 containers experienced less severe water stresses and required less time to return to normal transpiration rates than trees grown in other containers. The reduced stress levels and increased growth rates correlated with greater percent changes found in root lengths of smaller container-grown trees. Economic analysis after two growing seasons indicated a greater increase in value for #3 and #7 container-grown trees versus losses in value for some #45 container-grown trees. In comparison with trees from larger containers, trees from smaller size containers exhibited reduced transplant shock, decreased establishment time and increased growth rates, thus creating a quicker return on investment for trees transplanted from the smaller container sizes.