The month of March and throughout the rest of spring is a good time of year to prune shrubs in the landscape.
As you ponder which plants need to a little work, keep in mind the general guidance of pruning summer blooming shrubs (mockorange, shrub roses, rose of Sharon, caryopteris aka blue mist spirea and callicarpa aka beautyberry before growth begins so that you can easily see all of the stems that should be removed without leaves in the way and spring flowering shrubs after they have finished blooming to be able to enjoy the full floral display. In a botanical sense, summer bloomers produce flowers on current season (2025) growth, so removing certain stems won’t have a significant impact on enjoyment of their various attributes while spring bloomers bloom on wood that was produced the year previous (2024); just the opposite is the case for spring bloomers such as lilac, forsythia, viburnum and dogwood.
Why Prune?
Before taking a tool to the shrub, it’s important to have a purpose in mind, much like investing money with a financial advisor or stockbroker. There are 4 main reasons:
Right From the Start – Training
Most shrubs benefit from regular pruning. In the first year after planting, it’s best to remove only broken or diseased stems. In the second year, the goal is to establish the overall framework of the shrub and enhance its natural form so it matures into a structurally sound specimen. An even distribution of stems throughout is the objective for young shrubs, so strive to balance stem growth high and low and side to side. The good news is that shrubs planted in suitable growing locations should require less pruning as they mature.
Maintaining Good Health
Thinning is a good technique for broadleaf shrubs. The technique is to remove stems that are 4 to 5 years old at the base of the plant. The most common pruning mistake is to make the cut at 3 inches to 2 feet off the ground, which often leads to the retention of problems such as borers and cankers. The benefits of thinning are many – increased airflow through the canopy which reduces foliar diseases, increased sunlight that results in more and bigger blooms and eventual reduction in height since the older and taller stems are removed. Many gardeners have the desire for shorter plants as well as healthier plants.
Improving the Looks – Flowers, Fruits, Attractive Stems
Too many stems left in a shrub puts a drain on the energy reserves in a shrub. Removing some of them encourages enhanced appeal of the ones that remain. Removing broken and underdeveloped flowers and attractive features in a plant draws attention to the ones that are functioning as intended. A good example is with red twig dogwood. One of the most attractive features of this plant is the deep red colored bark which is evident year-round. In the Midwest in winter, red bark is welcome since the bulk of the landscape is white, brown or grey. Removal of the old, non-vigorous stems encourages ones in the 1-4 year age group to predominate which improves the looks of the plant.
Reducing Size
Finally, reducing size is a major reason to prune. The most common question I am asked as a horticulturist is “How far can I cut plant X back?”. Of course, the answer is that it depends on the age and species of the shrub, but cutting back in one fell swoop is usually an action leading to disaster. Still, size reduction can be accomplished, best done by removing the oldest stems at the ground level, as the oldest ones tend to be the tallest ones; thus, height reduction is achieved.
Pruning tools
Three basic tools are used to prune shrubs – a hand pruners that cuts with a scissors action, a lopping shears (basically a hand pruners with longer handles) and a pruning saw that cuts on the pull, not the push and pull. If the stems are large or thick at the base, a small chain saw is also a good tool. Two tools that are not recommended are hedge shears and anvil pruners, as they cause more damage than is desirable.
