How to maintain a cedar hedge - watering, fertilization, winter protection and pruning. Undemanding, cedar trees are fairly resistant to diseases and insects

If finding enough time for garden maintenance is a problem, a cedar hedge might be your answer. Cedars are gorgeous and undemanding, rustic and fairly disease-resistant: cedars will provide you with the privacy you need to enjoy your backyard without demanding too much time in maintenance.


A cedar hedge does not require much care. Planted in rich, well-drained soil and in full sun, cedars can live 60 to 80 years.


Cedars are able to tolerate a week without rain. If after 5-7 days rain is still not in the weather forecast, give your hedge a thorough watering so that moisture penetrates right down to the roots.

For optimum watering:

  • Install a soaker hose on top of the soil directly over the root balls of your hedge.
  • Water for one hour, once per week.
  • Watering in the evening and out of the sun is preferable so you don’t scorch the foliage, and always water long enough for the water to penetrate (short watering periods will only dampen the surface of the soil).


Since you added phosphorous-rich fertilizer when you planted your hedge, there is no need to fertilize any more during the first year.

After the first year:

  • Add fertilizer at the beginning of May in an even layer, extending one foot on either side of the hedge, then again at the beginning of June and once more at the beginning of July.
  • Never apply fertilizer after mid-July so that the trees have enough time to prepare for winter.

The most common insects

Insect attacks constitute the most common cause of disease in cedars.


What are they? – Small nocturnal moths which lay their eggs in July and August in cedar hedges. Larvae over-winter in leaflets, and when they awake in the spring, they feed on the foliage. Damaged leaflets will change colour, yellowing first then turning brown. At the end of May, small caterpillars form cocoons and by mid-June, the moths emerge.

Identifying them – When you see small white moths in your hedge, particularly at the end of the day, you know you have an infestation.

Treatment – Annual pruning will help get rid of the eggs. You can also use contact insecticide to control leafminer populations.

Spider mites

What are they? – Not spiders in fact, or insects; they are tiny (less than 1 mm) arthropods that suck plant fluid from foliage.

Identification - A large-scale infestation will be apparent through discoloration of the foliage.

Treatment – The easiest way to treat them is with a strong blast of water which will destroy their webs. You can also spray with an insecticidal soap.

Winter protection

Ensure a healthy cedar hedge

Cedars are very resistant to our harsh winters. On the other hand, there are other conditions that can cause a lot of damage.

Install wood lattice, rigid winter fencing and geotextile to protect exposed trees from:

  • Blowing snow from snowblowers and accumulations from snowploughs
  • De-icing salt

Pruning a cedar hedge

There are several reasons to prune a cedar hedge: to manage insect populations, to improve foliage density, to control the size and shape of the hedge, and to enhance the value of your property.

There are three types of pruning:

Trimming to ensure healthy growth

Take out your pruning shears in the spring to cut out dry, dead or broken branches.

Maintenance and shape pruning


You can trim a cedar hedge most anytime of the year without harming it, but there are better times, and that would ideally be between June 20 and August 1, with a larger window from May until late September.

What to prune

During the initial years after planting, only prune the sides, maintaining a base that is larger than the top. A cone-shape or pyramid-shape for the hedge allows the sun to penetrate and ensures better resistance to the weight of snow. Thus, the base will be twice as large as the top.

Topping involves trimming the tops of your cedars when they have reached the height you want, or the maximum height allowed by municipal by-laws. Aim for a rounded shape.


  1. Identify new growth – this will be a lighter green than the rest of the tree.
  2. Trim 1/3 or a maximum of half the new foliage. Cedars are not able to produce new growth on old wood.
  3. Keep part of the new growth so that the cedar continues to grow and fill out.

Rejuvenation pruning

This type of pruning is done in the spring or in the fall on hedges that have been ignored for a number of years. In order to avoid permanent and significant damage to the hedge, it is advisable to have the work done by an experienced tree technician.

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