Planting a cedar hedge: spacing and steps

A cedar hedge lasts about twenty years, but it gets planted in a weekend. What you decide that day (the spacing, the depth, the soil preparation) can't be fixed afterwards: nobody moves forty cedars three years later because they're too close together.

Here's what to plan before you start.

How far apart should cedars be?

You often hear "60 cm, period." That's too simple: the right spacing depends on how wide the cedar will be once it's fully grown.

The rule: space cedars at one half to two thirds of their mature width.

Why not just plant them close together?

• Too close, the cedars compete for water and light. The hedge fills in quickly, but after a few years it thins out at the bottom. And a cedar that loses its lower branches never grows them back: old cedar wood doesn't resprout.
• Too far apart, the hedge never closes up. You'll have a row of trees, not a hedge.

Our product pages list the mature width. Divide it by two: that's your spacing.

Dig a trench, not holes

Dig one trench along the whole length of the hedge rather than one hole per cedar. It's more work on the first day, but much less watering for five years. In a trench, roots spread through loosened soil and share the same water. In separate holes, each cedar stays trapped in its hole, surrounded by hard soil.

• Width: two to three times the width of the root balls, so 60 to 80 cm for cedars in standard-size pots.
• Depth: exactly the height of the root balls.
• Bottom: rough it up to break the layer packed down by the shovel, but don't dig any deeper. The root balls should sit on undisturbed soil so they don't sink.

Plant at the right level

As with any tree, the root flare (where the trunk widens at its base) should stay visible, at ground level. A cedar planted a few centimetres too deep turns yellow at the bottom by the second year.

Scrape the top of each root ball before setting it in place. If the root flare is hidden under potting soil, that's your guide, not the top of the root ball.

Stretch a string from one end of the trench to the other and line the cedars up with it. A wavy hedge shows for twenty years.

The soil

Cedar isn't fussy, but it hates two things: having its roots in water all the time, and running short of water often.

• Backfill with the original soil, with no more than one third compost.
• In heavy clay soil, add compost, not sand: sand mixed into clay turns as hard as concrete.
• If water stays at the bottom of the trench after rain, fix the drainage before planting: no cedar survives with drowned roots.

Basin, mulch and watering

Make a continuous basin along the hedge, then spread 5 to 8 cm of mulch over the whole strip, leaving 10 cm clear around the trunks.

Lack of watering is by far the main reason cedar hedges fail in Quebec. A potted cedar arrives with few roots for a lot of foliage, and it loses water all year, even in winter, when the frozen ground gives it none.

• The first year: one long watering a week, soaking the whole strip, not cedar by cedar.
• The second year: every two weeks in dry weather.
• Every fall, every year: a deep watering before the ground freezes. That reserve of water is what helps the hedge get through winter.

The browning you see in spring on so many hedges is almost never a disease. It's a lack of water over the winter: the foliage lost water that the roots, in frozen ground, couldn't replace.

The first few years

Don't prune the first year: let the hedge take root. Start pruning in the second or third year, once the cedars touch.

Prune the hedge into a trapezoid: wider at the bottom than at the top. A hedge cut straight, or wider at the top, shades its own base, which thins out for good.

Prune in June, after the spring growth, and if needed a second time in late August. Never during a heat wave, and never just before the frost.

What about deer?

In much of Montérégie, deer eat cedars. They can strip a young hedge down to the wood in a single winter.

If you see them in your area, protect the hedge from the first winter with netting or a temporary fence. It's a bit of work, but much less than replacing a hedge in spring.

Not sure about spacing, drainage or which cedar to choose for your yard? Write to us with the length of the hedge and a photo of the spot: we'll get back to you.