Flowering also is poorer in quality. The older canes, as is the case in lilacs, usually are infested with oyster shell scale, borers or some other pest problem. Height reduction, thinning and improvement of flower quality can all be done in late winter before bloom by taking out the oldest and weakest canes at or near the ground line. This also reduces height without removing the healthiest flowering canes. The sprouts from the base will flower the second season and replace those left the previous year.
Some Gardeners remove a few canes each winter.
This is a sound practice for most deciduous, spring-flowering shrubs, especially if the plant is noted for attractive stem color, as in the case of shrub dogwoods, such as the red osier. Canes of these shrubs, when older than three years, lose their brilliance and often become grayish or brownish. Remove about one-third of the canes, choosing the oldest and weakest each winter. This way, a shoot never overgrows and always maintains a healthy look. Heading-back from the top, if needed, usually is confined to a few odd branches.