BLACKSBURG, VA -- Many landscape trees are started in-ground, then sold as bare-root ''liners'' to producers who plant them in large containers to grow. To minimize wind damage and to facilitate transport from potting areas to growing beds, the liners are often buried deeper than necessary. This deep planting of liners results in "finished" container plants with deep structural roots, important foundations of root systems responsible for trees' health and stability. Deep structural roots are thought to contribute to physiological stresses resulting from oxygen deprivation.
J. Roger Harris and Susan D. Day from Virginia Polytechnic Institute and State University reported on their study of planting depth on pin oak and littleleaf linden trees in HortScience. "Green industry professionals are concerned about the increased number of landscape trees showing abnormally deep structural roots", Harris said. "Yet, the consequences of deep planting in production containers or the consequences of any adjustments made to planting depth at the time of transplant on growth in the landscape have not been reported for many species."
Harris and Day planted container-grown liners of pin oak and littleleaf linden trees in 50-L containers with the first main lateral roots (structural roots) at substrate-surface grade or 10 cm or 20 cm below grade (deep planting). Trees were grown in the 50-L containers for two growing seasons and in a simulated landscape for three additional seasons after transplanting, either with the top of the container substrate at soil level or with some roots and substrate removed so the original structural roots were just below the soil surface (remediated).
The experiments showed that deep planting pin oak -- but not littleleaf linden -- slowed growth during container production, but this effect did not continue after transplanting. Remediation of the 20-cm-deep pin oaks slowed growth during all three post-transplant years
|Contact: Michael W. Neff|
American Society for Horticultural Science