How to Trim Hedges: Timing, Technique, and the Mistakes That Kill Them

Most people trim hedges wrong. They grab the electric trimmer on a random Saturday, give every hedge the same flat-top haircut, and wonder why their boxwood has bare patches and their arborvitae looks like it’s dying from the inside out.

Here’s the thing: hedge trimming is not mowing. Different species need different timing, different techniques, and different levels of aggression. Cut a boxwood in late fall and frost kills the new growth. Cut an arborvitae into old brown wood and that section stays bare forever. Shear a privet once a year when it needs three to four passes and it turns into a wild tangle.

I’ve maintained hedges on my property for twenty years. Some of them I’ve rescued from terrible shape. One arborvitae row I inherited was so badly trimmed that the lower half was permanently bare. That one I couldn’t fix. Here’s what I’ve learned about doing it right.

When to trim hedges: the timing calendar

The single most important factor in hedge trimming is when you do it. Get the timing right and the plant heals fast, fills in thick, and looks great. Get it wrong and you’re fighting disease, frost damage, or bare spots.

Late winter to early spring (February through April) is the best time for most hedges. The plants are still dormant or just waking up. Hard pruning done now gives the plant an entire growing season to recover. This is when you do your major shaping and any renovation work.

Late spring to early summer (May through June) is the time for touch-up shearing on formal hedges. New growth has hardened off enough to handle cutting, and the plant still has months of growing season left to fill in.

Late summer (August through September) works for a final light trim to neaten things up before winter. Keep it light. Heavy cuts this late don’t heal before cold weather arrives, and the new growth they trigger is tender and frost-vulnerable.

Avoid trimming in late fall and early winter (October through January). Cuts made now expose fresh tissue to freezing temperatures. The plant can’t heal, and frost can damage the cut surfaces. The exception is a quick removal of storm-broken branches, which should come off regardless of season.

Formal vs informal: two completely different approaches

Before you pick up any tool, decide what kind of hedge you have. The University of Maryland Extension draws a clear distinction between formal and informal hedges, and they require entirely different maintenance.

Formal hedges are sheared to precise geometric shapes. Think boxwood borders, clipped privet walls, and sculpted yew. They require two to four trimmings per year and the goal is crisp edges and uniform density. Formal hedges need the trapezoidal shape rule (more on that below), and they’re maintained primarily with hedge shears or powered trimmers.

Informal hedges are rows of shrubs that grow in their natural form. They might get shaped once or twice a year, but the goal is a natural look, not a razor edge. Informal hedges are maintained with hand pruners and loppers, using thinning cuts to remove the oldest wood and keep the plant healthy. Shearing an informal hedge into a box shape defeats the purpose and suppresses the flowering that makes most of these plants attractive.

If you’ve got privacy shrubs and hedges planted as a screen, most of those are informal hedges. Let them grow naturally and just manage the height and width with selective pruning.

The shape rule everyone ignores

This is the single biggest mistake I see in residential hedge trimming: flat sides.

A hedge should always be wider at the bottom than at the top. The ideal shape is a gentle trapezoid. Narrower at the top, wider at the base, with sides that taper slightly inward as they go up.

Why? Sunlight. If the top of the hedge is as wide as (or wider than) the bottom, the upper branches shade out the lower ones. The bottom of the hedge thins out, goes bare, and eventually dies. You end up with a hedge that looks great from above and terrible from the side.

The taper doesn’t have to be dramatic. Even a slight inward angle of 10 to 15 degrees gives the lower branches enough light to stay dense and green. This applies to every formal hedge species. No exceptions.

Species-by-species trimming schedules

Every hedge species has its own rules. Here’s what actually works for the most common ones.

Boxwood

Boxwood is the most popular formal hedge plant for good reason. It takes shearing beautifully and stays dense. But it has limits.

When to trim: Thin in late winter (December through February) when temperatures are above freezing. Do your main shearing in early June after the spring flush has hardened off. Never shear in late fall because new growth won’t harden before frost.

How much to cut: Never remove more than 25% of total growth in a year. Violate this and you can kill mature specimens outright. For drastic size reduction, use a staged two-year approach: remove half the oversized branches in year one, the other half in year two, both times in early spring.

Key technique: Alternate between shearing (surface trimming for shape) and thinning (selective interior cuts for air and light). Shearing alone creates a dense shell with dead interior. Reach in with hand pruners and remove some interior branches every year or two to let light and air penetrate. This is especially important for English boxwood, which is prone to boxwood blight in humid, still air.

Privet

Privet grows fast. Thirty centimeters or more per year in good conditions, up to 5 meters tall. That speed is both the appeal and the headache.

When to trim: Major trimming in late winter to early spring, before the growing season kicks in. Hard pruning deadline is the end of February for deep cuts. Summer pruning should be light maintenance only because heavy summer cutting risks stunting growth.

How often: Young privet needs multiple trimmings per year. Two passes is the bare minimum. Three to four is more realistic if you want clean lines. This is why some homeowners are moving away from privet entirely. It’s a hedge that demands your time.

Renovation: Privet’s saving grace is its tolerance for hard pruning. You can reduce height by one-third to two-thirds and it rebounds, provided you leave enough growth nodes intact for regeneration. Shape it as a trapezoid (wider at the base) to prevent the lower branches from dying out from light starvation.

Arborvitae

Arborvitae is the hedge species most often ruined by bad pruning. There’s a biological constraint that separates it from boxwood and privet, and most homeowners don’t know about it.

The critical rule: Arborvitae only grows from newer green wood. The terminal portions of branches are the only parts with buds that generate new shoots. Cut into old brown wood and nothing comes back. That section stays bare. Permanently.

When to trim: Late February through mid-April. The optimal window is mid-spring after new growth appears, because arborvitae grows on new wood and spring cutting encourages vigorous regeneration. Emerald Green Arborvitae follows similar timing: late winter to early spring before new growth starts.

How much to cut: Maximum one-third removal per year. This isn’t a suggestion. This is the line between a hedge that fills in and one that develops permanent bald spots.

Height reduction: Gradual only. Remove approximately one foot per year. Every cut must stay in green, viable wood. If your arborvitae hedge is three feet taller than you want it, that’s a three-year project. There’s no shortcut. Cutting it down to the desired height in one pass will leave you with bare sticks on top that never recover. Our Green Giant Arborvitae guide covers growth patterns in more detail.

Yew

Yew is unique among needle evergreens. While arborvitae, juniper, and pine cannot regenerate from old wood, yew can. This makes it the most forgiving conifer hedge you can grow.

When to trim: Late winter to early spring before new growth. Final trim deadline is September. Cutting after September into dormancy causes brown patches because the plant can’t heal before it shuts down for winter.

Renovation capability: Yew tolerates severe pruning that would kill any other conifer. You can coppice it to 6 to 8 inches above ground to force new low branching, though recovery takes multiple years. For overgrown hedges, use a three-year protocol: year one, cut the top to 6 inches below your desired final height. Year two, reduce one side’s width. Year three, address the opposite side. This staged approach prevents shock while allowing progressive size reduction.

Annual limit: Despite yew’s regenerative ability, the one-third maximum annual canopy removal rule still applies. Yew grows about 12 inches per year, so plan accordingly.

Holly

Hollies (Nellie Stevens, American, Japanese) are evergreen hedges that tolerate regular shearing well.

When to trim: Late winter through early spring for major shaping. Light shearing in early summer (June) for touch-up. Holly berries develop on the previous year’s growth, so heavy shearing in summer removes the berry-producing wood.

Key technique: Holly responds well to both shearing and selective pruning. For formal hedges, shear to shape. For informal screens, use hand pruners to thin the oldest wood and maintain natural form. Hard pruning to reshape an overgrown holly is best done in late February. It may take two growing seasons to look good again, but hollies are resilient.

Photinia (Red Tip)

Photinia used to be everywhere. Now it’s a cautionary tale. Entomosporium leaf spot has devastated Red Tip Photinia across the Southeast and California. Pruning timing is critical for managing this disease.

When to trim: Winter only, while the plant is dormant. Dormant pruning avoids triggering the flush of new red growth that the Entomosporium fungus targets. Avoid summer pruning entirely because those tender red shoots are the fungus’s favorite food.

Disease management: Thin the interior for air circulation. Remove and dispose of any branches showing leaf spot (don’t compost them). Avoid overhead irrigation that keeps leaves wet. If your photinia is severely infected, honestly consider replacing it with Skip Laurel or another disease-free alternative.

How to rescue an overgrown hedge

You moved into a house with hedges that haven’t been touched in years. They’re ten feet tall, bare at the bottom, and wider than your sidewalk. Here’s how to bring them back.

Iowa State Extension recommends two approaches for overgrown deciduous hedges:

The three-year renewal method. Year one: remove one-third of the largest, oldest stems at ground level in late winter (March or early April). Year two: remove half of the remaining old stems, thin out some new growth, and keep several well-spaced vigorous new shoots. Year three: remove the rest of the old wood and shape the new growth. This method is gentler on the plant and keeps some screening throughout the process.

The severe one-time method. Cut the entire hedge to 4 to 6 inches above the ground in March or early April. This triggers a massive flush of new shoots during the growing season. The following late winter, select and keep several strong, healthy shoots per plant and remove everything else. Then head back the keepers to encourage branching. This works for privet, lilac, forsythia, dogwood shrub, and honeysuckle. The hedge looks terrible for a full year, but it recovers faster overall.

For overgrown evergreen hedges, neither method works if the plant has dead zones in the interior. Arborvitae, juniper, and pine cannot regrow from bare old wood. If your evergreen hedge is bare inside, your options are limited: either maintain it at its current size or remove and replant. Yew is the one exception. It regenerates from old wood and can be renovated using the three-year staged approach described above.

What tools you actually need

You don’t need much. Here’s what covers 95% of residential hedge work.

Hand pruners (bypass type). For cuts on branches up to 3/4 inch in diameter. Use these for thinning cuts, removing individual branches, and working inside the hedge. A $30 pair of Felco 2s or Corona BP 3180s will last a decade. Skip anvil pruners for hedges because they crush stems instead of cutting clean.

Hedge shears (manual). For shearing formal hedges. A good pair of manual hedge shears gives you more control than a powered trimmer and is quieter, lighter, and better for small hedges. They’re also the right tool for the final detail pass after a powered trimmer does the bulk work.

Powered hedge trimmer. For large formal hedges where manual shears would take all day. Electric (corded or battery) works fine for most residential hedges. Gas trimmers are heavier, louder, and only worth it for very large properties. An 18 to 22 inch blade handles most residential hedges.

Loppers. For branches 3/4 inch to 2 inches in diameter. You’ll need these for renovation pruning when removing old, thick stems from the base of the hedge.

What’s overkill: You don’t need a pole trimmer unless your hedge is above head height and you’re not using a ladder. You don’t need a chainsaw for hedge work.

Five mistakes that kill hedges

Flat-topping. Making the top as wide as the bottom. Lower branches die from shade. Already covered above, but it’s worth repeating because it’s the most common mistake I see.

Shearing without thinning. Shearing creates a dense outer shell. Over time, the interior dies from lack of light and air. Alternate shearing with selective interior thinning every year or two. Reach in with hand pruners and remove some of the oldest, thickest stems at the base.

Cutting arborvitae into brown wood. This is permanent damage. There’s no recovery. Always keep your cuts in green, active growth.

Trimming at the wrong time. Late fall pruning followed by a freeze. Summer shearing on photinia followed by leaf spot. Spring pruning on spring-flowering shrubs that wipes out the blooms. Match the timing to the species. Our tree pruning timing guide covers the same principle for trees.

Neglecting the base. A hedge that gets wider every year eventually shades out its own lower branches. Each trimming session should remove slightly more from the top and sides than you add back. If you’re maintaining a formal hedge, set a string line at your desired height and width and stick to it every time.

Check for nesting birds before you cut

Birds nest in hedges from March through August. Some species start earlier in mild years.

Before any major trimming, watch the hedge for a few minutes. If birds are flying in and out frequently, or if you see nesting material like twigs, feathers, and grass being carried in, wait. An active nest with eggs or chicks means hands off until the young fledge, which typically takes three to four weeks.

In the US, the Migratory Bird Treaty Act protects active nests of nearly all native bird species. Destroying an active nest is a federal offense. Beyond the legal issue, hedges are critical nesting habitat in suburban landscapes. A few weeks of delay is a small price for keeping songbirds in your yard.

The safest trimming windows are late winter (February) before nesting starts and late summer (August through September) after most fledglings have left. If you need to trim during nesting season, check the hedge carefully first.

When to hire a pro vs DIY

Most hedge trimming is a DIY job. If you can operate an electric trimmer and stand on a stepladder, you can maintain hedges under 6 feet tall.

Hire a professional when:

• The hedge is above head height and requires ladder work with a powered trimmer. Hedge trimmers and ladders together are a bad combination for amateurs.
• You’re doing a full renovation on a large overgrown hedge. The volume of material and the size of the cuts involved make this a bigger job than most homeowners expect.
• The hedge runs along a property line and you need clean, professional-looking results. A landscaper with the right equipment does in 30 minutes what takes you three hours.

Expect to pay $65 to $100 per person per hour for professional hedge trimming. A 100-foot hedge at 6 feet tall typically takes a two-person crew about 2 hours, so roughly $250 to $400 including cleanup. Getting it done right with a professional service means choosing someone who actually knows plants, not just someone who owns a trimmer.

The bottom line

Match the technique to the species. Trim boxwood and privet in late winter with touch-up in summer. Handle arborvitae with extreme caution and never cut into brown wood. Take advantage of yew’s rare ability to regenerate from hard pruning. Always shape hedges wider at the bottom than the top. And if your hedge is overgrown, don’t panic. A patient three-year renovation gets most deciduous hedges back in shape.

Good hedge maintenance starts before you pick up the trimmer. Know what you’re growing, know when to cut it, and know how much to take off. Get those three things right and your hedges will stay thick, green, and healthy for decades. For help picking the right hedge species in the first place, our privacy shrubs and hedges guide ranks 12 top picks by growth rate, deer resistance, and zone. If you also have shade trees that need professional attention, our tree trimming cost guide covers what to expect by size and species. And keep your spring tree and shrub care on schedule for the best results year-round.