Garden

What to Do About Yellowing or Bare-Spotted Cedar Hedges

Unsightly bare patches may be ruining your cedar's aesthetic. Here's how to fill out your flagging hedge.

By Conway Lum /

Cedars can be plagued by bare spots for a variety of reasons. Here’s how to keep a full and flourishing appearance

Q: We had to severely prune back a shrub between two very tall columnar cedars, and now there are large bare spots showing on the cedars where they were pressed against it. Will this grow back now?

A: Yours is not an uncommon problem. Cedars can be burdened with bare spots for a number of reasons. No matter how or where the bare spots are on your cedar, there are actions that you can take to repair and improve the aesthetics of the plant.

First, keep hedging cedars trimmed regularly. The sides as well as the top need shearing annually, at the very least. This will keep the trees relatively rigid and prevent some of the problems that can be caused by snow load during the winter months. A secondary shearing in late summer is very beneficial as a means to keep them dense and neat.

Also, ensure that no other plant material grows up to and against your hedging cedars, as a lack of light or a complete sheltering will kill those areas of the hedge. Keep in mind that plants in front of the hedge need to be trimmed as they grow so that they don’t rub against it.

Add new plants strategically, keeping in mind their growth habits, height and width to ensure they are positioned far enough away from the hedge to avoid contact. Any part of the hedging that has had limited light for a period of six months or longer will start to suffer and decline.

Regrowing your cedar

Regenerating growth from needle-less mature stems within the tree is unlikely. The only option for filling barren spots within the hedge is some reconstructive surgery or reconfiguration of the branching.

Using soft plant ties or vinyl ties, or a similar pliable stretch material, you can move branches by redirecting and securing them to other branches within the tree.

These ties are strong enough to hold the branches, yet pliable enough not to girdle or strangle them as they grow. I have pulled and secured branches quite aggressively, with an end result of a complete repair and filling-in of the bare spots.

Cedars that yellow at the end of summer

Toward the end of summer, the leaves (needles) on many cedar varieties show small amounts of yellowing. This is not uncommon and is actually quite normal and labelled as “flagging.”

Although it is not a result of an insect or disease, and is generally part of an inherent thinning process, flagging can also be a sign of a lack of water throughout a hot summer. A thorough, deep watering with a sprinkler for two hours every two weeks through hot spells should help to prevent your cedar trees from flagging.