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Sometimes a shrub needs a sharp edge.
Horticulturists agree that for most shrubs, selective pruning that retains their natural form is healthier, more attractive and much easier on the gardener than shearing them into sharp, severe shapes.
But sometimes, in some situations, shearing -- clipping all the branches in a shrub to create an even surface -- works. In Chicago's Grant Park, for example, where Bruno Maciuszek, 80, has been pruning the formal hedges in the European-style gardens around Buckingham Fountain since 1959. He's the Chicago Park District's senior shrub man, and he figures he's got around 20,000 plants on his beat.
Though sharp hedge shears are traditional and healthiest for the plants, power trimmers have made shearing faster and easier. Still, maintaining sheared shrubs is labor-intensive and requires repeated attention through the season. Those are among the reasons they are less popular than they used to be, as Maciuszek can testify. Since he started, when the Prudential Building was just going up, the majority of the sheared hedges in Grant Park have been replaced by less formal plantings.
But if you're going to do it, expert pruners have some advice about shearing.
Where to shear: On a hedge made of plants that are tough and resilient enough to take the abuse, such as privet, yew or boxwood, usually in a rather formal garden or to create boundaries or privacy. Shearing is stressful, and only some shrubs can handle it and stay relatively healthy.
When to shear: Shear two or three times a season or whenever the hedge seems shaggy. You will need to do this repeatedly because each shearing will stimulate new growth, according to Cass Turnbull of Seattle, who has a yard-maintenance business and is author of "Cass Turnbull's Guide to Pruning."
Maciuszek first shears in late April after new growth has begun. He returns once or twice during the season on the boxwoods and yews and more often on the privets.
What it does: Shearing makes cuts in the middle of branches, called heading cuts (although with power trimmers it often amounts to shredding the wood). This type of cut makes the plant think it's been attacked, so it rushes out new leaves to perform enough photosynthesis to survive, according Turnbull. The frantic new growth will be dense but weak.
How to shape: Choose a style that is pointed, rounded or flat on top. In any case, it must widen toward the base -- what John Sosnowski, horticulturist in charge of the hedge and maze gardens at The Morton Arboretum in Lisle, Ill., calls an "inverted keystone." Sunlight will be able to reach the spreading lower branches so the hedge doesn't die out at the bottom.
What to leave: Always leave some foliage so the shrub has enough leaves to live. On most plants (yew and privet are exceptions), if you cut back into bare wood, new leaves won't sprout.
How experts keep it straight: The traditional way is to pound sticks into the ground; run strings between them, checking them with a carpenter's level; and use the strings as cutting guides. To cut the top of Chicago's Grant Park hedges, Maciuszek balances his gas-powered trimmer where it's comfortable, about hip-high, and since he's 5 feet 11 inches tall and not growing, the hedges stay pretty straight (and mid-Bruno-sized). Sosnowski uses a laser level on a tripod to shoot a line down each of the 36 different sheared hedges he oversees. "It's like a pool table. Perfectly straight and level," he says.
How to thin: Since light can't penetrate the dense surface growth, inner branches will tend to die out. Turnbull suggests you take hand pruners, reach into the middle of the shrub and remove those dead branches at the base. This will help air and light get into that zone. If the hedge is tall enough to be seen only from the side, let the sun shine in by reaching up with hand pruners to cut out much of the dense top growth. More light means more food for the plants. And over time, in shrubs such as yews, the added light will help the hedge fill in.
How to rejuvenate: In winter, when the plants are dormant, take loppers and cut all stems close to the ground. Because the root system remains, new stems will sprout. After a year or two, start clipping their branches into the form you eventually want. With several years of careful attention the hedge will grow back to size.
How to start a formal hedge: Choose plants that can stand shearing (see accompanying story). Plant them in spring, spacing them so that when they are mature, their branches will slightly interlace. Plan the hedge's eventual shape (remember, widest at the bottom). Leave plants alone for the first season. In the late winter, while they are dormant, cut main branches back by about half and the rest within a few inches of the ground. This will promote dense branching. Once a network of branches is formed, begin shearing the shrub into its eventual shape.------
SHRUBS FOR HEDGES
Here are some shrubs that tolerate shearing into formal hedges relatively well. For best results and to minimize labor, choose a variety that naturally stays narrow (the jargon is "columnar") and grows not much taller than you want your hedge to be.
ARBORVITAE: Some of these flat-needled evergreens can work in sheared hedges if trained from the second year. They must be pruned carefully, never taking off too much foliage, because they will not regrow needles from bare wood. They need full sun.
BOXWOOD: A traditional European hedge plant, it does well in sun to part shade. Even the best varieties are marginally hardy in Chicago's Zone 5 climate and need some shelter; they may show damage from severe winters, drought or if exposed to severe winds or road salt.
PRIVET: Long used for hedges, privet now is considered invasive because its berries are distributed to natural areas by birds. Shearing before it flowers in late May will reduce berries. It needs full sun and loses its dark green oval leaves in winter. Ligustrum amurense is hardy in Zones 3 to 6.
YEW: This genus of long-lived needled evergreens will sprout foliage from bare branches to some extent. A good hedge variety is the columnar Taxus x media 'Hicksii.' It will grow to 12 feet or more but can be kept lower if it is carefully trained from the second year. Yews can handle sun or partial to full shade but will not tolerate wet soil.
TOOLS FOR SHEARING
Here are tools for shearing hedges. Keep hand tools clean and sharpen them once or twice a season.
Long-handled shears: These make clean and, therefore, healthier cuts than power trimmers. Also, for tall hedges, you'll need a ladder and it's safer to trim with hand tools rather than power tools when you're up on a ladder.
Hand pruners: Look for bypass blades, which pass each other, rather than anvil blades, which crush a branch between them. Use for thinning and removing deadwood, selective pruning of most shrubs and clipping topiary and low boxwood hedges.
Power trimmers: Available with gas engines (most powerful but loud and polluting), corded electric (quieter, cleaner, less powerful) and cordless electric (even less powerful). Trimmers are a blunt instrument that tear branches, thereby opening wounds to disease. They are available with poles and with articulating heads for pruning the tops of tall hedges. Always wear ear and eye protection. Keep your eye on extension cords and don't use power trimmers with children nearby.
"Cass Turnbull's Guide to Pruning" (Sasquatch Books, 317 pages, $19.95)
"Creative Homeowner Complete Trees, Shrubs & Hedges" by Jacqueline Heriteau (Creative Homeowner, 239 pages, $19.95)
"Pruning Basics: Tools, Techniques, Timing" by David Squire (Sterling Publishing, 128 pages, $12.95)
www.plantamnesty.com: Hilarious but sad photos of mistreated shrubs.
www.taunton.com/finegardening/pages/gvt030.asp: On the Fine Gardening magazine Web site, a video clip of John Sosnowski of The Morton Aboretum in Lisle demonstrating shearing techniques.
www.findarticles.com/p/articles/mi_m1082/is_n4_v42/ai_20912192continue: From Flower&Garden magazine, an article by Lee Reich on pruning and shearing hedges.
Beth Botts writes about home and gardening topics for the Chicago Tribune, a Tribune Publishing newspaper.