One of the most common questions about landscape maintenance is “When should I trim that plant?”
Fortunately, for most flowering plants, it is also a simple answer: “Within one month after they finish blooming.”
This would include most of the most common “woody ornamentals” such as azaleas, dogwoods and rhododendrons. Knowing the logic behind this advice helps to understand why.
Most spring-blooming plants in the northern U.S. bloom on “old wood.” In other words, those spring flower buds were formed the year before.
Therefore, if you trim that type of shrub late in the growing season (late summer, early fall) or before it blooms in the spring, you will remove those flower buds and ruin your “flower show.”
So then, just to repeat, if you trim flowering shrubs within one-month after they bloom you will be in rhythm with the flower show.