Trimming a Deciduous Hedge
by John Emmanuel
TRIMMING A FORMAL DECIDUOUS HEDGE can be a tricky business, and the larger the hedge, the more challenging the task becomes. The biggest challenges are getting the top of the hedge level and making sure the “batter”—the slight inward slope from the bottom of the hedge to the top—is even. Eyeballing the whole process can sometimes work, as long as only one person is involved and that person has a sharp eye and fair amount of stamina. But to ensure a visually pleasing result, and to prevent conflicts of judgment if two or more people are involved in the job, the best solution is to construct a template that tells you exactly where to shear. The hedge shown here is a large hornbeam (Carpinus betulus) hedge enclosing the east side of the Monocot and Aquatic Gardens at Wave Hill in the Bronx, but the technique is adaptable to smaller hedges using other plants, such as privet. The best time to undertake this project is in late spring, after the hedge has made its first new growth of the season.
1. To construct the frame of the template, we use 12-foot steel reinforcing bars, purchased at a construction supply company, plus an equal number of three-foot bars. (Of course, the length of the taller stakes should be adjusted to the dimensions of the hedge you’re trimming.) To make the outline, we use white synthetic twine, because it stands out against the hedge. Other tools consist of a tape measure, assorted bamboo stakes to assist in measuring, a lug hammer, and a stepladder.
2. Before constructing the template, it’s important to determine the basic dimensions: how wide do you want the base and the top of the hedge to be, and how tall? First, we measure the distance from the central trunk of the endmost hornbeam to the outer edge of the base of the hedge. Once that distance has been established, we cut a piece of bamboo to the same length so that we can measure the placement of the other short rebar stakes correctly. The short rebar is inserted at intervals of approximately 10 feet.
3. We then connect the stakes with twine, securing it with a half-hitch knot. Slight adjustments may be necessary because of irregularities in the plants or the ground.
4. Inserting the long bars is easiest with two people. The first person stands on the ladder and inserts the bar at the top of the hedge; the second person guides the bar through the branches to the ground. A measurement is established along the base between the tall bar and the nearest small bar. We then cut a piece of bamboo to that size to mark the distance; the rest of the tall bars are then pounded in at the same interval. When pounding in the long bars, we make sure that the upper end of the bar is sticking out at the top of the hedge; if it were pounded flush, we’d never get the thing out.
5. We then stretch a line along the top of the hedge to connect all the tall bars. At this point it’s a good idea to stand back to see if the top edge of the hedge, as established by the white twine, is level. If it sags here or rises there, we get back on the ladder and adjust it.
6. Next, we stretch a line between the point where the tall bars meet the top edge of the hedge to the short bars, to form the hypotenuse of a right triangle. This line ensures that the slope of the sides of the hedge will be even.
8. Again, step back to make sure that the planes of the twine framework appear relatively flat and even. Building the template takes time the first go-round, but once you’ve recorded the measurements, all you’ll need to do the next time is to hammer in the stakes and attach the line.
7. Now we tie a line midway up one of the hypotenuse lines and connect it to all the hypotenuse lines around the hedge. This line should be kept taut enough to establish an imaginary plane up the side of the hedge from the base to the top. As you string the lines, make sure they don’t get snagged on branches.
9. The actual shearing goes quickly. We start cutting near one of the lines and work our way toward the other lines. If we accidentally cut the line, we simply retie it. Because of the inevitable drift of a line or two, the surface plane may rise up here, down there. If that occurs, we simply tinker in those areas until the entire hedge plane is flat.
10. Once you’ve achieved a nice, even outline, you can get away with eyeballing any subsequent cuts the hedge may need during the rest of the season. H
MAKING A PERMANENT TEMPLATE
You can dispense with the need to erect a template every year by leaving the stakes in the ground and retying the white line yearly. Rebar rusts quickly, and will blend into the naked branches. A more elaborate framework can be constructed by welding or wiring the rebar together, preferably just after the hedge has been planted. The hedge will eventually fill out the frame, which provides a permanent template for trimming. When the hedge drops its leaves, the framework can be viewed as winter “sculpture.”–J.E.