When to trim your trees and shrubs

Some shrubs benefit from an annual or frequent hard cutting back. For example, red osier dogwood, which is grown for its colourful stems, should be pruned every few years, as the youngest stems have the brightest colour. And a number of somewhat tender and late-flowering shrubs, such as butterfly bush, hills-of-snow hydrangea and blue spirea, should be cut back each spring.

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