How to Trim Hedges

Process of trimming hedges by hand

The Spruce / Jayme Burrows

Project Overview
  • Working Time: 3 hrs
  • Total Time: 1 - 2 hrs
  • Yield: 12-foot hedge
  • Skill Level: Beginner
  • Estimated Cost: $0 to $15

Trimming hedges the right way keeps them full from top to bottom. The best way to trim established hedges is to use an outward-flaring angle to allow the lower side branches to receive enough sunlight to grow and fill in the body of the hedge. For this method, you'll erect boundaries made of string that you can follow as you trim the branches. Newly planted shrubs require a different trimming strategy for the first year or two until the shrubs reach a more mature stage. Follow these steps to learn how to trim hedges the proper way.

When to Trim Hedges

The proper time to trim a hedge depends on whether the plant is non-flowering, or flowering, and when it sets its buds. A non-flowering hedge should usually be trimmed every six to eight weeks during the growing season and less frequently as the weather cools.

For flowering shrubs, it's important to time the trimming so it doesn't interfere with their bloom cycle. Spring-flowering shrubs are best trimmed immediately after they bloom. Summer-flowering shrubs should be trimmed in the late winter or early spring before active new growth is underway.

What You'll Need

Equipment / Tools

  • Hedge trimmer (hand or cordless)
  • Hand pruner
  • Mallet or hammer
  • Tape measure
  • Stepladder (for tall hedges)
  • Line level (optional)
  • Carpenter's level

Materials

  • Tall stakes or poles
  • String

Instructions

Overhead shot of materials needed to trim hedges

The Spruce / Jayme Burrows

How to Trim Hedges

  1. Prepare for Layout Strings

    Use hand pruners to cut away unruly branches of an oversized, overgrown hedge if necessary to allow the string guidelines to be stretched out straight and taut for an accurate guideline.

    Removing offending branches from the shrub

    The Spruce / Jayme Burrows

  2. Set the First Pair of Stakes

    Drive a stake into the ground at one end corner of the hedge, using a hammer or mallet, The stake marks the spot where you want the bottom end corner of the hedge to fall.

    Set the stake in slightly from the reach of the longest branches. Angle the stake slightly so it "leans in" toward the top of the hedge. The amount of lean is based on expected sun exposure: On the side that will face direct sunlight, make the lean relatively slight; on the shady side, make the lean more pronounced.

    Pound in a second stake at the opposite corner of the hedge on the same side, angling it as with the first stake. For precision, measure the distance from the trunk or main stem of the nearest shrub so the distance is the same for both stakes.

    Tip

    You can usually get by with four guide strings—one at the top and one at the bottom of each side of the hedge. On very tall hedges, though, a third interim string on each side might be helpful.

    Driving the first stake into the ground

    The Spruce / Jayme Burrows

  3. Set the First String

    Attach a long string from one stake to the other, near the lowest branches of the shrubs. Make sure the distance above the ground is the same from one side to the other. If the ground is level, the string should also be level; sloped ground will require a sloped string. Use a line level to adjust the string for level if necessary.

    Setting up the first string

    The Spruce / Jayme Burrows

  4. Set the Upper String

    Repeat the process to set an upper guide string marking where you want the upper edge of the hedge to fall. Ensure uniformity from end to end by measuring up from the lower string, and position the upper string at the same distance from the ground at each end. If the ground is level, use a line level to check the string's orientation so it's perfectly horizontal. On sloped ground, it's best to measure from the ground to guarantee it's uniform from end to end.

    Use a hand pruner to remove any branches deflecting the installed string guides to make the strings straight and taut from end to end.

    Setting up the second upper string

    The Spruce / Jayme Burrows

  5. Set the Remaining Stakes and Strings

    Repeat the process to set the other pair of stakes and strings on the other side of the hedge. Check that all strings are straight and taut and prune any branches touching or deflecting the strings.

    Hold a long carpenter's level across the hedge, just touching the top strings, and adjust the strings so they are level side-to-side. This helps you trim your hedge so the top face is flat and level regardless of the ground slope.

    Setting up the remaining stakes and strings

    The Spruce / Jayme Burrows

  6. Trim the Top of the Hedge

    Trim the top face of the hedge so it is flush with the top guide strings. Hold the hedge trimmer as level as possible as you trim.

    Position the ladder into the hedge for safety so you are leaning into a tall hedge while pruning.

    Beginning to trim the top of the hedges

    The Spruce / Jayme Burrows

  7. Trim the Sides and Ends of the Hedge

    Trim the sides of the hedge to create planes that are as even as possible with the guide strings. Use hand pruners to cut through thicker branches, if necessary. It's normal to have some indentations and thin spots in the hedge but the trim will stimulate new growth to fill them in.

    Trim the ends of the hedge so they are squared up and vertical. Or, you can angle the edges inward in the same fashion as the sides of the hedge.

    Trimming the sides of the hedge

    The Spruce / Jayme Burrows

  8. Feed and Water the Shrubs

    Water and feed hedges with compost or slow-release fertilizer, depending on the needs of your plants. Trimming is stressful for hedge shrubs and this TLC will help them respond with new growth.

    Watering the shrubs after trimming

    The Spruce / Jayme Burrows

How to Trim New Hedges

After ​planting a hedge, consider the following method for trimming:

  1. Pinch back all new growth during the first year to induce low branching and give the shrubs a fuller shape. Use hand pruners or fingers to eyeball the shape as you pinch back the new growth. You don't need staked string guides for new hedges.
  2. Begin trimming back the upper branches a bit shorter than the lower branches to allow sufficient sunlight to reach the bottom branches.
  3. Continue to trim the hedges like this for one to two years.
  4. When the hedge is full-bodied and begins to become shaped like an inverted vase, switch to the steps above which use a string guide to achieve the classic flat top and sides.
FAQ
  • What is the best way to trim my hedges?

    The best way to trim mature hedges is to use a guide made from string and stakes. Trimming a mature hedge by eyeballing it will make the shrubs uneven on the top and sides.

  • What's the best month to trim my hedges?

    The best month to trim any hedge depends on the type of plant you're going to trim. Some hedges need trimming at certain times to keep them healthy. For example, the best time to trim boxwood and other evergreen shrubs is early to late spring (depending on the type) but it is typically avoided in late fall.

  • How much should I trim off the top of a hedge?

    Do not trim more than 1/3 of the entire height off the top of the hedge. Trimming too much can potentially fatally injure the plants.