Late winter is a great time to assess your garden's pruning needs.
Shrubs that are well-maintained can add structure and interest to your garden all year. They usually need less maintenance than herbaceous plants and can be long lived.
Proper pruning will keep your shrubs healthy and appealing, will encourage more prolific blooms and will manage shape and size.
- Broken, damaged or diseased branches, along with those that rub together, should be removed. Cut them below the damaged area, and discard the branches if they show signs of disease.
- For branch by branch shaping, cut back longer branches to the crotch or a bud, and you'll maintain the shrub's natural shape and keep it looking neat.
- For thinning, remove about one-third of the larger branches each year back to their crotch. This promotes blooms and new growth, and it controls woodiness while keeping the shrub's shape.
- Renewal pruning: Shrubs that bloom later than June 15, and bloom only on new growth, should be cut back to 8 to 12 inches from the ground in late winter. Examples of shrubs that benefit from renewal are butterfly bush, blue mist spirea, Russian sage, and barberry
Not all shrubs will tolerate this annually, so research your shrub before you use this approach. An alternative to annual renewal is to complete the process over a three-year period.
- Rejuvenation is the most drastic approach, usually reserved for severely overgrown shrubs. The shrub is cut back almost to the ground. It can be a good alternative to rescue a well-established root system under an aged shrub.
- Spring blooming shrubs (those that bloom before June 15) can be pruned using any of the techniques listed here. Pruning should be done immediately after bloom.
- Cuts should be made just above a bud or leaf or at the crotch of the branch.
- A 45-degree angle parallel to the stem bud or leaf is ideal.
- Use the correctly sized sharp tool to make a clean cut.
- Draw cut or scissor action pruners work well for branches up to 1 inch in diameter.
- Lopping shears work well on branches up to about 2½ inches in diameter.
- For bigger branches, use a pruning saw.
- In late winter and early spring, prune summer blooming shrubs and candidates for radical surgery (rejuvenation).
For junipers and arborvitae, snip back new growth to an upward growing side branch to maintain natural shape. Do not cut back to wood.
- In mid-spring to early summer, prune spring bloomers right after they bloom.
Mid-May is best for broadleaf evergreens (boxwood, holly, Oregon grape holly) and roses.
For Mugo pines, using the fingers, snap off one-third of the new growing tips while in the "candle" stage, in which young needles are in a tight cluster.
Colorado State University Extension has research-based answers to your horticulture questions. ask.extension.org.