Living walls

Flower & Garden Magazine, July-August, 1998 by Lee Reich

The individual bushes that make up the ideal hedge should melt together into a swath of greenery -- or "red-ery" in the case of red-leaved plants -- to form a living wall. These living walls, like those of brick or wood, define spaces and screen out unwanted views or unwanted stares. A well-grown deciduous hedge dense with leaves and twigs will carry on this job year-round.

The natural growth habit of the bushes that make up a hedge should influence its shape. Many short branches thoroughly clothed in small leaves can give barberries a formal rounded shape. Lanky stems, originating each year mostly from ground level, make forsythia a fountain of yellow flowers. True, you could force barberry into the shape of a vase or make forsythia formal and rounded. As a rule, however, let the type of bush -- rather than your pruning tools -- decide whether your hedge will be formal or informal.

PRUNING YOUNG PLANTS

In order for a hedge to provide a physical, psychological and/or visual barrier, each plant must be thick with leaves from head to foot. To create dense and uniform growth, you have to choose appropriate species, plant them correctly and, just as important, prune the plants soon after you set them in the ground. The pruning operation is simple but brutal: Cut the whole plant down to within a few inches of the ground. This drastic pruning encourages vigorous regrowth and low branching.

If your new plants are already well-branched to ground level, it's not necessary to prune so severely. Plants such as beech, hornbeam and Nanking cherry naturally branch well right to the ground. Plants growing in containers may be similarly well branched if they are old enough and were correctly pruned as hedge plants in their youth. With these well-branched plants, trim back the main stem and laterals by one-fourth to one-half so that they continue to branch farther as they grow.

Once you give your hedge plants their first pruning, let them grow unmolested for the rest of their first season. If your hedge is to be informal, also leave your hedge alone its second and third season.

For the formal hedge, trimming and shaping should begin in its second season. Shorten main stems by about half their length and remaining branches to just a few inches while the plants are still dormant. The goal is to promote dense branching and, again, only a slight shortening of stems is needed on plants already twiggy from top to bottom.

Even though it has yet to reach its final size, begin shaping your formal hedge. No matter what the shape of the hedge, the top always should be narrower than the bottom. Otherwise, the bottom will become shaded, and the shaded portions will die leaving gaps in the hedge.

MATURE HEDGES

Once your hedge has reached the desired size and shape, your job is to keep it that way.

If your hedge is informal, use a lopper to cut some of the oldest stems to ground level or to low, young branches. Then use your hand shears to shorten any stems that are still jutting out clumsily. Other plant species will try to invade your hedge, and they can be easily overlooked among the more tangled branches of an informal hedge. So as you prune cut away or grub out the invaders. Prune early blossoming bushes right after their blossoms fade and late bloomers while they are still dormant. When you finish pruning, the line of arching stems of your informal hedge should look like a breaking wave advancing across the landscape.

Prune your formal hedges with either manual or electric hedge shears. To maintain its crisp form, a formal hedge needs shearing at least once a year. The actual frequency needed depends on two factors: how crisp you want the lines of your hedge and the vigor of the plants. Do your first shearing of the season while the plant is in full leaf, preferably after the initial growth flush has subsided so that regrowth is minimized. Where winters are very cold or with hedge plants of questionable hardiness, avoid shearing after midsummer. You may stimulate soft new growth that can be damaged by low temperatures.

When you shear, hold the cutting blades parallel to the surface you are creating. Shear almost to the point where you previously sheared. Start low on the hedge, and work your way up so that it's easier to reach across the top. If your hedge is rigidly geometric, stretch a taut line a few inches above the desired cutting range as a guide.

If you want flowers on your formal hedge, you have to accept a more ragged look. A hedge that flowers early in the season should be sheared right after the flowers fade. Depending on the plant species, you may get one more shearing in, but you must allow sufficient time for regrowth and raggedness on plants that flower mostly or only on year-old stems. Of course, you can keep shearing back growth on a plant like the flowering quince, which flowers on older wood. In this case, though, all the flowers will be buried within the hedge's branches.

With a formal hedge that flowers later in the season, you can cut to your heart's content before growth begins in the spring. But soon after growth begins, don't touch those new stems or the hedge won't produce flowers.