Reducing Surface Rooting of Trees with Control Planters and Wells

Abstract

Control of surface rooting was explored in a study of fruitless mulberry (Morus alba) and zelkova (Zelkova serrata). After 3'A growing seasons, average amounts of roots were reduced substantially in the top 8 inches of soil by PVC control planters and by wells that placed trees 18 inches below grade. Among trees in planters and wells, however, amounts of surface roots differed greatly, and the tendency of roots to return to surface layers may be partly associated with soil compaction and poor aeration. Mulberry roots returning to the surface layers were, on the average, smaller and zelkova roots fewer than the unconstrained roots of control trees of the two species. For a given trunk size, mulberry roots were much more massive than zelkova roots. Avoiding species with massive roots remains extremely important in selecting street trees.