Don't touch that shrub!
Q. Is fall a good time to prune and fertilize shrubs? Are there any shrubs I should not prune in fall?
A. So what should you prune this fall? Basically, the general rule of thumb is to prune immediately after a shrub has finished blooming. Reducing a big plant's size over several years is your best bet at achieving the shape you desire.
Removing no more than a third of any plant over the course of a single season is the correct way to prune.
Often pruning is ignored for a number of years and this creates a weak and overgrown plant. Regular pruning does keep a plant shapely and encourages growth.
When you prune this time of year, it stimulates new growth. Tender new growth will freeze with an early frost, and pruning in fall also has the possibility of killing the plant.
This is the time of the season that plants are in the process of going dormant. Pruning will stress and weaken the plant as it is going into its dormancy season. Woody plant stems have 'food making' ability and by removing the stems, you are removing some of the plants ability to make food. In addition, if you are pruning while the weather is still warm, the plant will send up sap that makes the pruning 'wounds' close up much more slowly than if pruning was done when the plant was dormant.
Fall is also the time of year when fungi and disease spores spread. Opening wounds on fall pruned shrubs increases the risk of disease.
Spring and summer flowering shrubs and trees start setting their new buds immediately after they have bloomed. So pruning your azaleas, rhododendrons, spirea, magnolia, flowering specimen trees, lilacs and forsythia at this time of year will result in fewer blooms, if any, for next season. These plants have already formed next year's buds and are ready to bloom as soon as spring shows its "head." The safest time to prune spring/summer bloomers is within six to eight weeks right after their flowers fade.
Other shrubs and trees that have bloomed in July and August should be pruned in late winter/early spring before the new growth starts because these plants will be developing buds during the spring of the year. Basically, the safest time to prune non-spring bloomers is when the plant is dormant.
Yes, you are right! The weather is great and you see all the work that needs to be done thinking you will save yourself time in the spring. However, the only pruning you should be doing at this time of year is to remove any diseased areas or damaged wood. Relax and start dreaming about all those spring buds you saved from destruction!
- Bev Krams
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines. Call (847) 298-3502 or email northcookmg@gmail.com.