Background: As with most tasks, the adequacy and thoroughness of the preparations determine to a great extent the successfulness of the venture. Boxwood have a root system which is very conducive to transplanting. It is fibrous, slightly larger than the drip line of the plant, with a depth of approximately one third the height of the plant. The most ideal time to transplant boxwood is the fall, and spring is the next preference. The reason for this time schedule is that if moved during September, the root system has October and November to begin establishing itself even though the top appears dormant. Any break in the weather during the winter months will bring about root growth and the spring months prior to the flush will be accompanied by root growth. This level of root development is very important in preparation for the dual stresses of heat and drought which the summer will place on the plant. Therefore, spring transplanting leaves much less time for this important root development Actually a break in the weather during the winter when the ground is not frozen is an acceptable time to move plants as long as the major cold of winter is thought to be past, i.e. mid to late February for most of the Mid-Atlantic states but many mild winters, I have been able to plant all through most of the winter.
Preparation: If one knows six to twelve months prior to transplanting, that plants are to be moved, root pruning is a practice which may be beneficial. A spade is inserted to its full depth around the circumference of the root ball just inside the drip line of the plant. No attempt is made to lift the plant. The purpose of cutting the side roots at the drip line leaving the bottom roots of the ball intact is to force additional root growth within the ball prior to transplanting. After cutting, many new roots will form and branch right at the line of this pruning cut. This root prune line should be marked in some way because the final cut of the root ball at the actual time of transplanting should never be within this line but outside of it since the new root growth will take place on the outside of the location of the cut at the root tips.
Digging: The soil around the plant to be moved should be moist. If dry conditions exist, thoroughly saturate the soil one day before the move. This will allow ample time for the water to dissipate. Do not soak the plant and then try to move it. The added weight of the water and the softness of the soil will cause the root ball to fall apart.
When determining where to make the final cut around the plant, check the stem to determine whether it is in the center of the plant. If it is, the drip line of the plant is a reasonable guide for your cut (or outside of the root pruning line). If the stem is off center, then the stem should be the primary guide. One should center the stem but not cut inside the drip line. The depth of the root ball will be approximately one-third the height of the plant. Boxwood do not have deep roots but it is necessary to get a solid ball. A spade with a face approximately 16″ long should be used in order to get the depth of root ball desired on larger plants. A normal round point shovel would be fine for a plant 12″-15″ tall because the shovel would penetrate 10″, but on a 30″ plant a spade penetrating 15 inches is desirable.
Make a circumferential cut with the spade angled slightly inward. After cutting once around, cut around again to insure that all lateral roots have been severed. At this point, a prying action can begin. After inserting the shovel fully, pry slightly in various locations around the plant in order to gently lift it free. When working with a plant larger than 24″, two people, each with a spade, prying together, work most effectively. When prying constantly check the integrity of the ball to insure that it is not breaking or cracking. The ball should be lifting as a unit. After a point, the ball should “feel” free, even though it may feel heavy. The ball may then be lifted from the hole. This is done by one or two people, each grasping at the base two or more major branches, and lifting the ball up and out of the hole.
Planting: The planting site should be adequately prepared ahead of time. The hole should be significantly larger than the circumference of the root ball but not deeper. The reason for not digging deeper is that the plant should not sink. The final level of the plant should not be deeper than it was previously. Humus can be mixed into the surrounding soil to lighten it since boxwood need well-drained soil. To facilitate drainage in heavy soil, angering holes may be dug at various points in a bed and filled with organic humus. The auger may be as small as a long electrical type of bit on a drill or as large as a post hole auger on the back of a tractor. The size auger is totally dependent on the area to be dug and the size of plants going into the area.
Once placed in the hole, stabilize the plant prior to filling the hole to determine that the placement and depth are correct. When planting multiple plants in the same general location, one may stabilize all the plants in the holes in this manner to check the placement of the group to determine whether one or more plants need adjustment. After all minor adjustments have been made, then filling in around each can be completed. When filling, use soil that is loose and not lumpy in order to minimize air holes. While filling in the dirt, water liberally creating a “muck” in order to eliminate any air pockets and settle the dirt around the root ball. This technique is preferable to stomping the dirt down with your foot since stomping compacts the soil but does not settle it around the ball.
Stephen D. Southall
English Boxwoods of Virginia