By David G. Hallauer
Kansas State University Research and Extension
If some warmer days have you ready to be outside, one of the things on your to-do list should be pruning deciduous shrubs. It isn’t difficult if you follow a few rules of thumb.
Start by determining the type of shrub you have by separating them in to one of three categories: spring flowering on wood produced last year, those that flower later in the year on current seasons’ growth and those that produce flowers, but have little ornamental value.
Prune the early spring flowering group immediately after flowering. Pruning now won’t hurt, but it will likely reduce flowering. Plants might include forsythia, lilac and mock orange.
The other two groups—those that flower on current seasons’ growth and those with flowers of little ornamental value—are best pruned in late winter/early spring. This would include Rose-of-Sharon, pyracantha, Bumald spirea and Japanese spirea.
Second, think about pruning according to three basic methods.
Thinning takes a shrub that is too dense and thins it out by removing inward growing twigs, cutting them back to a larger branch or cutting back to just above an outward facing bud. If the stem has a multi-stemmed growth habit, the oldest canes can be removed completely.
Heading back is removal of the end of a branch by cutting it back to a bud. This is used to reduce the height of a shrub or to keep it compact. Avoid cutting back to a uniform height as this may result in flush of unattractive growth at the tips of the cut area.
If you have multi-stemmed shrubs that are overgrown with too many older branches to justify saving young canes, consider rejuvenation pruning. This is where all stems are cut back to three to five inch stubs. This is not recommended for all shrubs but can work for spirea, forsythia, pyracantha, ninebark, little leaf mock orange, shrub roses and flowering quince.
You don’t have to go crazy, but there’s not need to be afraid of pruning. Spring pruning allows wounds to heal quickly without threat from insects or disease. Avoid the use of pruning cut treatments, as they may slow healing. For a guide to help direct your pruning work (with diagrams), check out K-State Research & Extension publication “Pruning Shrubs” available in your District Office or online at https://bookstore.ksre.k-state.edu/pubs/MF2998.pdf.