When to Trim a Cedar Hedge in Ottawa (and How Much to Cut)

The trimming window

The reliable window for trimming cedar hedges in Ottawa runs from late April to late October, when there is no frost or risk of frost. Fresh cuts leave tender tissue exposed, and a hard frost on a newly trimmed hedge can brown the cut tips.

Within that window, the timing you pick changes the result. A trim in late spring or early summer, after the flush of new growth, gives a crisp shape that lasts through the season. A trim later in summer or early fall is fine too, but growth slows as the weather cools, so the hedge keeps that shape into winter.

Why once a year is usually enough

Eastern white cedar grows steadily but not wildly. One trim a year, around the same time each year, keeps the height and width where you want them. Doing it on a regular schedule also means you only take off the new growth, which is quick work and keeps the hedge thick.

Skipping years is what causes problems. A hedge left for several seasons has to be cut back further, and that is where people end up cutting into bare wood.

The one rule: never cut into bare brown wood

Look into a cedar hedge and you will see a green outer layer of foliage and brown, bare wood inside. Cedars do not sprout new growth from that brown wood. If a cut goes past the green, the patch left behind may never fill in.

That is why a hedge should be trimmed a little at a time, and why it is better to start narrower and keep it that way than to try to cut an overgrown hedge back hard. See our guide to why a cedar hedge turns brown for what bare patches mean and whether they can recover.

What to check before you start

A few minutes of looking saves a lot of regret:

• **Check for nesting birds.** Nests of migratory birds are protected in Canada, and hedges are popular nesting spots in spring and summer. Look through the hedge first, and check Environment and Climate Change Canada's guidance on nesting periods for this region. If you find an active nest, leave that section alone.
• **Check the forecast.** Avoid trimming just before a hard frost, and avoid the hottest, driest days of summer, when freshly cut foliage can scorch.
• **Look for the green line.** Find where the green growth ends on each side so you know how far you can cut.
• **Plan the shape.** Keep the top slightly narrower than the base so light reaches the lower branches. A hedge that is wider at the top goes bare at the bottom.
• **Use sharp, clean tools.** Dull blades tear foliage and leave brown, ragged tips.

How to trim a cedar hedge

• Set a string line or use a straight edge to mark the height you want.
• Trim the sides first, working from the bottom up, in light passes.
• Cut the top last, level with the string line, with a slight taper so the sides lean in toward the top.
• Stop at the green. Do not cut into bare brown wood.
• Step back often and check the line from a distance.
• Rake or collect all the clippings. A pile left under the hedge can smother grass and hold moisture against the base.

What about trimming in fall or winter?

Late October is the end of the usual window. After that, leave shaping cuts until spring. The exception is safety: broken, hanging or snow-damaged branches can be removed when they are a hazard. Our snow and ice damage guide covers what to do after a heavy winter.

Trimming a hedge that has been left for years

An overgrown hedge cannot be brought back in one cut. If it is much taller or wider than you want, trim back to the green growth now and keep trimming a little each year. If most of the hedge is bare inside, it may not recover, and replacement can be the better answer. Our hedge replacement service covers that. Ask for a free look and we will tell you which one applies.

Looking after the hedge between trims

A trim is only part of the picture. Steady watering, especially in the first two years and in fall before freeze-up, matters as much. Our cedar hedge care guide walks through the whole year.