One of the most frequent questions we get here at Blooming Secrets is about pruning shrubs. Proper pruning not only maintains an attractive shape but it also keeps the shrub healthy. Pruning helps to thin out branches that will allow new growth to receive sunlight and to promote good air circulation which prevents diseases from starting or spreading. The two shrubs that we get the most pruning questions about are Crape Myrtles and Hydrangeas so we’ll use these as examples of how to prune shrubs properly.
We’ve discussed the “why” behind the task of pruning but it is equally important to know “when” to do the pruning and “how” to actually do it. First, I always view pruning as a spring to early summer chore. Pruning most shrubs in the fall can actually be harmful to the shrub as the purpose of pruning is to promote growth. The last thing you want to do is to prune the shrub only to have the new growth be damaged or killed by colder weather. Fall is a time of year when plants are going dormant and pruning at this time of year can really make the shrub prone to injury or it can even kill the shrub altogether. It is also particularly important not to prune spring flowering shrubs, such as Azaleas and Lilacs, in the fall as you are literally cutting the flowers off.
So, now that we understand why we prune shrubs and when we should do it the final question is how do we prune our shrubs? Before you start cutting you should take a step back and look at the shape of the shrub to make sure you are happy with its shape. As you scan the shrub take note of broken or damaged branches which should be removed. Now you’re ready to start pruning. You’ll want to make sure your cuts are made at a 45 degree angle about ¼ of an inch above a flower bud on the branch you are pruning. You can use a hand pruner for most cuts but if you have branches that are more than a ½ inch thick a lopping shear might be needed to make clean cuts.
Finally, let’s talk about how to apply these tips to pruning Crape Myrtles and Hydrangeas. Crape Myrtles can be pruned late in the winter into the early spring. You can even prune them when the growth first emerges but you don’t want to wait too long after that occurs or you will negatively impact the shrub’s flowers. All Crape Myrtles should be pruned even if it is done modestly as this has been found to produce more flowers. However, for some reason it seems that it has become a common practice to commit what is called “crape murder”. This involves pruning the shrub all the way down to the ground. This practice is not only unnecessary but it could eventually kill the shrub. No more than 1/3 of the shrub should be pruned at any one time.
Hydrangeas are a little more complicated in terms of when to prune them. Old wood hydrangea varieties should be pruned immediately after they finish blooming in the summer and definitely not in the fall. Old wood hydrangeas develop their flower buds for next year in August and September and pruning them too late in the season will lead to fewer blooms, if any, next year. Otherwise, pruning an old wood hydrangea is no different than pruning shrubs in the fashion that we mentioned above.
The other variety of hydrangea is known as a new wood hydrangea. These are hydrangeas that form their flower buds on new growth so it is easier to prune these shrubs and they are much more likely to bloom regardless of when they are pruned. While they can even be pruned in the fall I would recommend that they be pruned late in the winter for the reasons I cited earlier. It is sometimes tempting to even cut this type of hydrangea back to the ground level as it won’t negatively impact the blooms and it can help keep the shrub neat looking. However, doing this too often can actually put a lot of stress on the plant which can eventually weaken it significantly and make it susceptible to diseases and insect damage. Applying the 1/3 pruning rule that we’ve discussed before is a much more prudent approach.
Please check out our related article on how to prune lilacs and if you have additional questions about pruning shrubs please reach out to us through the “ask us” page of our website or on Facebook.