Roots of four-year-old, field-grown southern magnolia (MagnoliagrandifloraL.) were pruned in 1987 once during dormancy, following the first shoot growth flush or after the second growth flush, prior to transplanting in January 1988. By the end of the 1987 growing season, root pruning at all stages of growth reduced leaf number, tree height, trunk caliper, and total-tree leaf area and weight compared with unpruned controls. Total root weight was less for trees pruned during dormancy or following the first growth flush. Root pruning increased the proportion of fine roots (0 to 5mm-diameter class) to coarse roots (>5 to 10-mm diameter class). Shoot:root ratios were not affected by root pruning. During the first year after transplanting, root pruned trees grew at a slightly faster rate than unpruned trees but growth rates were similar for root pruned and unpruned trees the second and third year after transplanting. Trees required, at most, 1 year per inch of trunk caliper to become established in the landscape.