Tall hedges were once ubiquitous in home gardens, although they are planted far less commonly now in new landscapes.
Anyone who buys an old house with a tidy, formal hedge or who attempts to recreate that classic look with new plants quickly finds out why the popularity of hedges has drooped.
While they can be beautiful and enhance the privacy of a yard, hedges also require quite a bit of maintenance, so they turn off the time-crunched homeowner.
There’s no getting around the work required–short of yanking out the whole hedge–so you might as well do the job right and ensure the long-term health and beauty of the hedge you have.
Proper pruning isn’t just about keeping the hedge looking orderly, but also about helping the plants thrive.
Before pruning a hedge for the first time, be sure you know what kind of plants make up the hedge, advises Andrew Otting, a horticulturist with Scott Byron & Co., a Lake Bluff landscaping firm. Knowing what kind of plant you have will help you make wise choices on such things as when to prune.
Lilacs, for instance, should only be pruned immediately after their midspring bloom time is through. That’s because next year’s blooms are on this year’s new growth; pruning before much new growth has occurred protects the next spring’s round of luscious, fragrant lilacs.
There’s an entirely different timing concern with juniper hedges, says Dale Berthlein, landscape manager for the Libertyville landscaping firm Rocco Fiore & Sons. “The friction of a hedge trimmer’s blades can singe junipers on hot days, especially if the plants are really dry,” Berthlein says. His advice: don’t prune a juniper hedge any day that the temperature is over 90 degrees.
For almost any hedge plant, pruning should result in the top of the hedge being slightly narrower than the bottom–exactly the opposite of the shape an old hedge left to fend for itself will take.
The top of the plant is where more new growth is, so on its own the plant will naturally become top-heavy, explains John Sosnowski, a Morton Arboretum horticulturist whose duties include tending the institution’s recently renovated hedge exhibit.
“But a wide top blocks light from getting to the bottom of the plant, so it loses a lot of greenery down there and gets a dead zone at the bottom,” Sosnowski explains.
The hedge doesn’t need to taper off to a point at its top–unless that’s a look you’re after. Sosnowski believes the difference in widths should be barely noticeable.
To get a uniform taper on the sides, consider using three separate string lines paralleling the hedge–at the top, middle and bottom–for the first pruning, or even the first few, until you develop an eye for it.
Set up the bottom line to hang an inch or so farther out from the center of the hedge than the top line does, with the middle string halfway between them. The string lines then act as a guide for how far to prune the hedge when you are working at various heights on it.
String lines are also helpful for getting an even top, particularly on a neglected hedge that has developed a shaggy, uneven top.
One problem with using string lines is that if you really want a tidy look, you’ll need to get the lines into precisely the same positions every time you prune.
If that kind of fussiness is a bit much for you, at least take this step, recommended by Berthlein, to ensure that the finished hedge looks somewhat even: start at the tallest or widest part of the hedge. “If you just automatically start at one end without paying attention to what’s tallest,” he says, “you might get to that point and find out you can’t cut as low there as you’ve been doing down the line.”
Cutting too much off the extra-high or extra-wide part can create a dead zone where the plants can’t generate enough new growth. So establishing the amount to be cut off with the highest or widest spot in mind is a way of avoiding having to make severe cuts like that.
Some parts of the hedge may not be as tall or as wide as the dimension you have set; skip pruning them until they have grown to the line.
How much to cut off? Otting suggests that summertime pruning should only take off new growth, which is usually recognizable because its foliage is a slightly different green than other leaves, and its stems are less woody, more flexible than other branches. “It should really only be aesthetic pruning in the summer,” Otting says. “Winter and spring are better for serious pruning, where you take out internal branches.”
A few reasons: on deciduous hedges, which lose their leaves in winter, it’s much easier to see the branches and make judicious cuts; and the risk of opening plants up to opportunistic diseases that attack at new cuts is smaller in the winter.
On a hedge that has been left to go shaggy for a few years, it may not be feasible to cut off all the growth that has sprung up since the last pruning. The wood may have hardened too much to be able to put out new foliage, so the hedge will end up with a sparse-looking patch. Go light on those hedges, but if the hedge has had regular pruning, it’s OK to take off as much new growth as is needed to get the desired look for your hedge.
Finally, Sosnowski has a bit of advice for the new hedge-owner who doesn’t yet own hedge clippers. Spend the extra money to get one of the new battery-powered models. They combine the best attributes of gas-powered and electric-corded trimmers, he says.
Lightweight battery-powered trimmers are quiet like corded trimmers but don’t bring with them the hassles and hazards of stringing out a long extension cord.
