Why You Should Prune
To answer the question of when to prune flowering shrubs, we must first determine the reason behind the pruning. Do you wish to rejuvenate overgrown, neglected bushes through pruning? Or is this to be merely a routine pruning to maintain the flowering shrubs within certain dimensions? Each has its time and place. Typically, we wish to prune flowering shrubs in order to shape them or keep them within certain bounds, but we worry that we will miss out on this year’s blossoms if we prune at the wrong time—thus the well-founded fears beginning gardeners have about pruning. Before putting those fears to rest, let me tackle a very different question that some beginners have: Why bother pruning at all? If you have sufficient space to allow a plant to get as big as it can, is there still some incentive to pruning it? The answer is yes. The benefits of pruning flowering shrubs are real, and two of them worth mentioning here are as follows:
Routine Pruning, Rejuvenation Pruning, and Basic Techniques
Here is the general rule of thumb to know when to prune a particular plant:If you are undertaking a routine pruning, observe the shrubs’ blooming habits: As to how to conduct such routine pruning, the Purdue Extension sums it up by listing three techniques. We list them below, beginning with the mildest kind, and ending with the type that entails cutting the greatest amount of vegetation: If you are pruning flowering shrubs to rejuvenate them, the best time to prune is late winter or early spring. True, pruning early-flowering shrubs at this time will reduce or eliminate blossoming in spring that year, but the trade-off is in gaining healthier shrubs that will bloom more vigorously for the long run. Rejuvenation pruning is commonly done on overgrown lilac bushes. They are one of the shrubs that respond well to this kind of pruning. It is a drastic kind of pruning, but it is not as scary as it sounds, because each year you are only pruning out 1/3 of the branches coming out of the ground. You start with the oldest 1/3 the first year. The second year, you cut out another 1/3 of the oldest remaining branches. The third year, you prune out the oldest branches that remain, leaving only the youngest branches. The idea is to have the youngest (and, we assume, healthiest) branches take over and “become” the lilac bush. “Rejuvenate,” after all, means “to make young again.”
What About Evergreens?
Note that the above advice has been about pruning deciduous bushes, as opposed to evergreen kinds. Deciding on when to trim evergreen bushes is a bit more complicated because you first have to determine if the shrub in question is a broadleaf type (which, like the deciduous bushes, may be grown largely for its flowering display) or a needle-bearing type.
