Cedar (Thuja) is the most popular conifer used for hedges in Quebec, and for good reason! It provides year-round privacy and, with proper maintenance, can last for many years. Yearly trimming is essential to keep your cedar hedge healthy and attractive.
Why Trim Cedars?
Trimming cedar hedges serves two main purposes: to control their growth and to increase their density. Don’t take out the shears or hedge trimmer anytime to trim just about anything. For a beautiful, long-lasting cedar hedge, it’s best to trim it every year. Light, regular trims are more manageable than trying to restore a hedge that has overgrown.
When to Trim a Cedar Hedge?
You need to wait until the new growth, which is a lighter green colour than the older growth, is clearly visible. In Canada, the ideal time to trim is between late June and mid-September, depending on the region. During this period, cedars are in full growth and recover well from trimming. However, keep these tips in mind:
- Avoid Early Spring Trimming: Trimming cedars before the growth period starts can remove old wood that hasn’t yet produced new shoots.
- Avoid Heatwaves: Trimming cedars during very hot days can cause stress to the plants. Trim on cooler days or early in the morning or late in the day when temperatures are more moderate.
- Hydration: If municipal regulations permit, make sure the cedars are watered well before and after trimming during dry periods to reduce stress and promote a healthy recovery.
How to Trim a Cedar Hedge?
Remember that you should trim only the new growth, removing a maximum of 1/3 to 1/2 of it. For example, if the new growth is 6 inches (15 cm) long, you should trim 2 to 3 inches (5 to 7.5 cm).
Should the Top of the Cedars Be Trimmed?
The top of the cedars should be trimmed once they have reached the desired height. In the first years after planting, focus on trimming the sides, which typically lasts 2 to 3 years, unless the cedars were very small when planted. Aim for a base wider than the top to ensure sunlight reaches the entire hedge and to prevent snow accumulation in winter, which can cause branches to spread under its weight.
Which Tools to Use for Trimming Cedar Hedges?
For precise work, use hedge shears like those from the Garant Jardiner range. They provide a clean, smooth cut, allowing you to trim at your own pace while seeing your progress as you go. Opt for lightweight shears with high-carbon steel blades coated with Teflon. Some shear models even have telescopic handles to reach higher branches. For larger hedges, consider using an electric or gas hedge trimmer for faster results.
Fertilizing a Healthy Cedar Hedge
After trimming, don’t rush to fertilize! Conifers benefit from nitrogen-rich fertilizer (the first number) in early spring to promote new growth. Typically, a nitrogen (N) number of 10 to 15 is ideal for granular fertilizers. By the time you trim your hedges, spring fertilization has already passed, so wait until September to apply a potassium-rich fertilizer (the last number). This helps the cedars prepare for winter and come back strong the following spring.
Pro Tip for a Nice Cut
For a nice cut, it is essential to use tools with well-sharpened blades for clean, smooth cuts without leaving torn or crushed stem ends. Poorly trimmed branches present entry points for insects and diseases. Check the sharpness of your blades before each new gardening season and sharpen them as needed!