Hedges of estate quality don't grow naturally. Plants in thickets reach out to all sides, competing for light with their neighbors. Cutting back that competitive growth causes thicket plants to branch out densely and pack more leaves into less space. The best hedges result from careful tending through the first years, repeating that same cycle of expansion and reduction many times. Shaping to geometric forms only works well when the hedge approaches its final size.
Prune the hedges to shape during the first two years of the hedge's growth. Trim young hedge bushes to only 6 to 8 inches in height after planting. Before buds open the following spring, remove half the new growth from the year before. Prune half the annual growth again early in the second spring. Cut back sides as well as tops.
Shape hedges with more detail in the third year. Allow 6 to 8 inches of new growth before trimming back lightly. On average remove half the new growth in one trimming. Allow the hedge to fill in and trim back again. Total expansion of the hedge in one season shouldn't exceed 8 inches.
Prune any damaged or dead limbs in late winter, and remove any pockets of debris. Repair holes in the hedge by tying off limbs to stout stems and pulling them over to fill gaps. Use cotton cord which rots after one or two seasons. Tie to the plants with a loop, not a tight wrap.
Trim to a more precise shape using cotton lines as guides when hedges reach the desired final height. Drive stakes at four corners of the hedge. Tie cotton guide-lines between the post tops to mark the desired hedge dimensions. Level the lines with the sliding bubble level. Set the marker posts perfectly vertical by measuring with a plumb bob. Plumb bobs are simple pointed weights suspended from a string. Holding one up gives a perfect vertical line for sighting cuts and straightening posts.
Sight along the guide-lines to trim the hedge to a final squared shape with flat top and vertical sides. Make the first side cut lightly along the hedge bottom, allowing the upper hedge to fill in the vertical line during the growing season. Once the shape establishes well, take down guide-lines and simply cut back to the old growth.