Pruning Acer rubrum at Planting Impacts Structure and Growth After Three Growing Seasons

Branches present in the tree crown at planting can become obstructions in urban landscapes, requiring large pruning cuts later and possibly creating weak structure by growing upright to comprise a large section of the crown. Pruning at planting, currently a discouraged practice, could shorten or remove selected branches and thus improve the structure of a newly planted tree. Acer rubrum L. trees planted into soil from 170 L containers were pruned at planting to subordinate the largest primary branches, or not. Pruning induced a 26% reduction in total cross-sectional area in the five largest primary branches. This sizable reduction in growth on pruned branches resulted in a significant reduction in aspect ratio of the largest (11%) and three largest (10%) branches. The negligible pruning wound from raising the crown on pruned trees would result in little trunk dysfunction when branches are later removed for clearance, and the debris would be minimal. Tree height growth after three growing seasons was unaffected by pruning; the 8% slower trunk diameter growth might be difficult to recognize in a landscape. Bending stress required to tilt trunks three growing seasons after planting was equivalent with or without pruning.