How to prune and when
Washtenaw County Michigan flowers: annuals and herbaceous perennials
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The sooner you prune the better:
- The best time to prune azaleas is in early spring, before the plant puts out new growth. Although you'll be cutting off that year's blooms, it gives the plant the full growing season to fill out, and time for the new growth to mature before winter.
- Pruning while they are in bloom is next best, and gives you some cut flowers, or pruning just after they bloom lets you enjoy the flowers on the plant.
- Since most azaleas start growing next year's flower buds soon after they bloom, pruning after mid-summer cuts off next year's bloom. Late pruning also runs the risk of the tender new growth being killed in cold climates.
Before you start, look at the plant you intend to work on, remembering that branches which are shaded out often die back and become dead wood anyway. Remove these first, as the effect of removing them may alter the way you approach pruning the rest of the branches to maintain the shape of the bush.
Use clean cutters, and keep them clean as the work progresses, using a sterilizing solution such as denatured alcohol or a 10% Chlorox solution, particularly if any cuts are in infected wood.
Older plants may have a number of tall branches which need to be eliminated. Doing that over several years reduces the shock to the plant. Remove two or three of the tallest branches, taking care to cut back to a side branch which is heading in the desired direction, and which is about 1/3rd the size of the cut branch. Cut close to that side branch, as any stubs will die back to the side branch anyway, and leave dead wood which may become infected later.
Next year take out two or three more branches using the same process, spreading the pruning over a three year cycle. This approach will result in the plant sending out new growth near the base, and lets you manage the shaping of the plant to achieve a nicely shaped bush.