LAUSR

Field production of seedlings used to create nursery stock liners involves transplanting and root pruning that can alter root system architecture. Seedlings of eight species of trees commonly used in urban landscapes were selected based on the configuration of their woody lateral roots; Preferred (maximum gap between roots ≤90 degrees), Acceptable (maximum gap 120–150 degrees), and Inferior (≥180 degree gap—no lateral roots on one side). The lateral root configuration (LRC) of the seedlings was compared to the LRC one year after replanting. The number of lateral or regenerated roots alone was generally adequate to form an acceptable root flare (≥3 roots) one year after seedlings were replanted. The maximum gap in lateral roots as a seedling was not consistent with the maximum gap one year after the seedlings were replanted in most species. It often became larger. Neither lateral roots nor regenerated roots alone could reliably produce a root structure with an acceptable maximum gap between roots. Lateral roots and roots regenerated from the pruned end of the main root, together produced enough flare roots one year after replanting with a small enough maximum gap in the radial distribution for good stability. This information may be an initial step in developing criteria for seedling grading systems that will improve root systems of nursery stock grown for planting in urban landscapes.