My 20ft long cedar hedge is approx 14 yrs old, about 18ft high, and I cut off the tops last year for the 1st time. I have neighbors on the other side as well as a lattice fence that is 15ft high. I do not want to see my neighbors, and now I can see through the trees. From the stem, the branches extend 4ft easily, there is maybe 12″ of green growth. How do I encourage growth? Is it too late?
Thank you for sending your question to the Toronto Master Gardeners.
Careful pruning is important to achieve a robust cedar hedge.
To decrease a cedar’s height, remove no more than 20% of the tree’s height.
All new growth of cedars is produced in the green ends of branches. These may be trimmed back but must retain some new green growth as this species does not generate new growth from old wood.
If you trim some of the new growth you mention (being careful to leave some of the new green growth) your cedars should respond by producing more new growth.
When pruning, shape the bottom of the hedge wider than the top. This allows even exposure to sunlight and promotes growth of the entire hedge.
Since pruning stimulates new growth, it is best done in late spring and early summer. With pruning in late summer or fall, the new growth that emerges will be vulnerable to the coming cold temperatures and could be easily damaged.
Cedars generally do not require much, if any, soil amendment, as the root system spreads outward on each side, at twice the radius of the tree, accessing ample nutrients. But, if the tree leaves look pale, or unhealthy, then the addition of a fertilizer containing nitrogen and iron may help your hedge. Toronto Master Gardeners prefer an organic fertilizer such as a combination of bone and blood meal. Or, you could spread organic compost around the base of each tree trunk. Fertilize in early spring before new growth starts.
Another factor contributing to cedar health is providing adequate water. Cedars are able to tolerate a week without rain. So, if rainfall is inadequate, water your hedge thoroughly so that moisture penetrates right down to the roots.
Mulching around the trunk beginning about six inches from the base of the trunk will help the cedars retain moisture.
Good luck with your cedar hedge.