Cut any circling roots so they will not strangle the plant later on. If a shrub is pot-bound, use pruning shears or a serrated knife to make slices 1 to 2 inches deep going from the top of the root ball to the bottom. Make these slices in three or four places around the root ball. Pull the roots growing along the outside of the root ball away from the root ball. Research has shown that although this kind of pruning does not increase root growth after planting, slicing root balls enhances the distribution of new roots in the surrounding landscape soil.
New roots grow from behind the cut ends.
The soil used to fill in around the root ball of the newly planted tree or shrub is called backfill. Your best backfill will be the loosened original soil from the planting hole. Loosen and break up any clods of soil before backfilling. Clods in the backfill create undesirable air pockets around the root ball and could hinder root growth and establishment. Next, backfill the bottom half of the space around the root ball.