Trimming Hedges in August Heat — Plant Safety First

August is when hedges look the shaggiest and homeowners want them cleaned up the most. It is also one of the trickier months to actually do the work right. After more than ten years trimming hedges across Pickaway, Franklin, Fairfield, Ross, and Fayette counties, I can tell you that the difference between a hedge that bounces back in two weeks and one that browns out for the rest of the season usually comes down to timing the cut around the day’s heat and knowing which shrubs can handle a hard trim this late in the year.

Here is how I work every August hedge job, and the calls I make before I even unpack the shears.

Is August too hot to trim hedges in Central Ohio?

Yes for hard rejuvenation cuts, no for routine shaping. The heuristic I use on my own crews: if the forecast high is above 88 degrees, we move trimming to the next morning and only do light shaping that day. Anything more aggressive waits for a cooler stretch or pushes to early September. OSU Extension’s pruning guidance for landscape shrubs is clear that heavy cuts during heat stress can damage the plant’s ability to regenerate foliage, and what looks like a clean hedge on Saturday can turn into a brown wall by the following weekend.

On a Pickerington property last August, the homeowner had hired another outfit to cut their privet down hard at 11 a.m. on a 91-degree day. By the time I drove past two weeks later, half the hedge was crispy along the south-facing side. They called me in October to take it out. That work was preventable with a different start time and a lighter cut.

On a Circleville hedge job I did this Tuesday, we started at 6:45 a.m., wrapped by 9:30, and the hedge was back in shade by the time the air hit 80. That is the rhythm I run August trim work on.

Which hedges can I safely trim in August?

For most Central Ohio properties, these handle late summer shaping without much risk if you keep the cuts light:

• Boxwood: light shaping only, no more than an inch of new growth removed
• Privet: tolerant of August cuts, but stop before mid-September so new growth has time to harden off
• Yew: shape lightly, avoid cutting into bare wood, will not push new buds from old wood
• Holly: light tip cuts only, watch for spines, do not cut into structural wood
• Arborvitae and Emerald Green: shape the new growth only, never cut back into the brown interior

These I leave alone until later in the year or wait until early spring:

• Forsythia: prune right after spring bloom, not now
• Lilac: same, prune after bloom in May, not August
• Hydrangea (big-leaf): cutting now removes next year’s flower buds
• Rhododendron and azalea: avoid heavy work in heat, light deadheading only
• Spirea: depends on variety, but most do better with a late winter cut

On a Lancaster property last week, the homeowner asked me to shape his big-leaf hydrangeas in August. I walked him through why that would cost him next year’s blooms. He kept the hydrangeas, we shaped his boxwoods instead, and the property looked just as clean.

What time of day should I trim hedges in August?

Before 10 a.m. or after 6 p.m. The plant stress part is real, but the operator stress part matters too. Working hedge shears overhead in 90-degree humidity is how people end up in the urgent care. I run the same rule for my crew and for any homeowner who asks for advice: start at first usable light, take a break before the sun gets high, and finish in the evening if you have to.

Avoid trimming on days when storms are forecast within 24 hours. Fresh cuts on humid days with rain incoming invite fungal disease, especially on boxwood. If you see blackened tip foliage on your boxwood after a recent trim, that is most likely boxwood blight or Volutella, and OSU Extension has a fact sheet on disease management that is worth pulling up before you cut again.

What is the right way to cut a hedge so it grows back full?

The cardinal rule: keep the bottom of the hedge wider than the top. The mistake I see most often on Central Ohio properties is a hedge that has been cut into a perfect rectangle, where the upper foliage shades out the lower foliage. Within two seasons the bottom thins out, you can see through to the fence behind it, and the only fix is a hard rejuvenation that takes another two years to recover from.

The correct profile is a gentle taper. Wider at the base by 4 to 6 inches per side compared to the top. Light hits all of the foliage and the hedge stays dense from the ground up. This sounds small. It is the single biggest factor in whether a hedge looks good in five years.

On a Chillicothe boxwood hedge I have maintained since 2022, we keep that taper religiously. The homeowner has had to do zero rejuvenation work in three years and the hedge is denser now than the day I started.

Should I bag the clippings or leave them in the bed?

Bag them. Hedge clippings on the bed surface mat down, hold moisture against the crowns, and invite pests and disease. They also look unfinished. The leaf debris from boxwood especially should go to the yard waste pickup, not into the compost pile, because if there is any blight present it will spread.

For thicker clippings off privet or yew, I run them through a chipper on-site if the volume justifies it, or haul them off to the Pickaway County yard waste site. The cleanup is half the job. A trim that ends with debris all over the bed reads as half-done even if the shape is right.

How short can I cut a hedge in August?

For most species, no more than 10 to 15 percent of the current canopy. Anything more in this heat puts the plant into recovery mode at exactly the wrong time of year. The hedge needs its remaining leaves to keep photosynthesizing through fall and to store carbohydrates for winter.

If a hedge has gotten so overgrown that 15 percent will not do it, the right call is to wait until late February or early March for a hard rejuvenation cut. You will lose the look for a season, but the regrowth will be vigorous and the hedge will recover its shape by mid-summer.

On a Washington Court House property earlier this month, a client wanted a 6-foot privet taken down to 3 feet in one cut. I told her no. We took it from 6 to 5 in August, will trim it again lightly in early October if the regrowth allows, and the hard cut to 3 feet will happen next March. That phased approach keeps the hedge alive.

What about watering after an August trim?

Hedges that have just been trimmed are working harder than they look. The plant is allocating energy to seal cuts and push new growth at the same time it is fighting heat stress. A deep watering at the root zone the evening after a trim, about 1 inch over the bed area, helps the plant recover. Avoid overhead watering of freshly cut foliage in late afternoon, since standing water on cut surfaces overnight invites disease.

For established hedges in clay soil, which is most of Pickaway and Ross County, that means a slow soak with a soaker hose or a low-flow sprinkler running for 45 minutes to an hour rather than a quick spray. Clay soaks slowly. A hard spray runs off before any of the water gets where it needs to go.

Common August hedge mistakes I see

• Trimming at noon on the hottest day of the week
• Cutting hedges into a perfect rectangle with no taper
• Leaving clippings on the bed surface
• Going too short on a single pass
• Hard-pruning hydrangea, forsythia, or lilac at the wrong time of year
• Using dull shears that crush stems instead of cutting cleanly
• Skipping the post-trim deep water on clay soils

Quick August hedge checklist

• Check forecast highs and pick a sub-88-degree morning
• Confirm your species can handle a late summer cut
• Sharpen and disinfect shears between properties to avoid spreading disease
• Cut to a tapered profile, wider at the base
• Remove no more than 10 to 15 percent of canopy
• Bag clippings and clear the bed surface
• Deep water at the root zone that evening

Want a written quote?

If your hedges have gotten away from you this summer, or if you would rather not run shears in 90-degree heat, Lawn Harmony Landscaping handles routine and one-time hedge trimming across Pickaway, Franklin, Fairfield, Ross, and Fayette counties. Locally owned and operated, licensed and insured, with a 5.0-star Google rating.

Call (614) 425-9789 or email LawnHarmonyOhio@gmail.com for a free quote. Need a broader property cleanup with the hedge work folded in? Ask about our landscape and mulch bundle.

Service area: Circleville, Columbus, Grove City, Pickerington, Canal Winchester, Lancaster, Chillicothe, Washington Court House, and surrounding Central Ohio communities.