Why prune
Pruning shrubs can be done to promote plant health, improve form and maintain plants for foliage, fruit or flower production.

When to prune shrubs

• Shrubs that bloom on last year's growth, early in the season should be pruned immediately after they finish blooming. (examples: azalea, forsythia, lilac, Juneberry)
• Shrubs that bloom later in the growing season, on new growth and last year's growth should be pruned before the growing season commences or after blooming. (examples: potentilla, rose, weigela, mock orange)
• Shrubs that bloom only on new growth should be pruned before the growing season begins (example: clematis, spirea, hydrangea)
• Conifer shrubs can be pruned at anytime of the year, except shrubs from the pine genus (Pinus); see Conifer pruning
• Shrubs grown for their foliage or colorful stem should be pruned before the growing season begins (example: redosier dogwood, barberry, willow)

Types of pruning
Coppicing - Hardy shrubs that are grown for their foliage, stem coloration or flower on new growth may be pruned back heavily to the first pair of buds above the soil line.

Renewal pruning - To promote new growth, return the shrub to a desirable form or encourage growth in "hollowed out" shrubs, renewal pruning can be done by randomly removing about 1/3 of the oldest branches each year. Prune branches back to the stem; remove branches that are dead, diseased or rubbing against other branches.

Conifer pruning - Arborvitae, junipers and yews have lateral (side) buds that will sprout if the terminal (tip) buds are removed. Pruning cuts can be made anywhere along the branches to retain form and promote new growth. Shrubs from the Pinus genus (example: Mugo pine) rarely needing pruning, but can be pruned in the "candle" stage each spring. Remove up to two-thirds of the "candle," or newly expanded vegetative growth, to promote a denser shrub.

For more information, see the Extension publication, Pruning shrubs and trees, or contact the Department of Forest Resources Extension and Outreach at 612-624-3020.

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