When to prune, what to prune, how to prune is a perennial question. One person I know says “the best time to prune is when you have time”. Since most heavy pruning work is done in the winter, pruning in May is the time to focus on shrubs or small trees that have bloomed in early spring on old wood. They can be cut to either reduce size, enhance shape or to encourage abundant flowering next year. If you are planting or training an espalier on a wall or fence, you may need several pruning sessions in spring and summer. If you are pruning a hedge, cut it so that adequate light gets into the center of the plant. It is always wise to study the plant, observe how it naturally grows as well as how you what direction you want it to grow. First remove any dead, diseased, crossing or inward growing branches. Consider pruning as creating artful sculpture – it will be enjoyable and your final product will be more pleasing.
For the early blooming shrubs or small trees, once they are finished blooming prune if needed. Lilacs are a good example – I always prune mine back a bit so they don’t get too large and because pruning encourages larger blooms next spring. If your azaleas are too large and need to be reduced in size, then it is best to prune after blooming.
Following is a list of other spring blooming shrubs that can be pruned in May:
Camellia, cherry laurel (Prunus laurocerasus), Fothergilla, Mahonia, Photinia, Pieris, Pyracantha, Amelanchier, Spirea (spring blooming), Viburnum (do not prune them if you want the fruit), Weigela, witch hazel, Magnolia (spring blooming)
Only prune hydrangeas for the following reasons: dead branches, size is too large, or plant health is poor. Hydrangea plants fall into two categories. Some bloom on old wood and are pruned after flowering, versus those that bloom on new wood and are pruned in late winter. Prune back stems to just above a fat bud. Here are two for late winter pruning:
Panicle hydrangea (Hydrangea paniculata)
Smooth hydrangea (Hydrangeas arborescens)
And here are four for pruning after flowering are:
Bigleaf hydrangea (Hydrangea macrophylla)
Mountain hydrangea (Hydrangea serrata)
Oakleaf hydrangea (Hydrangea quercifolia)
Climbing hydrangea (Hydrangea anomalis susp. petiolaris) should not need pruning unless it is too large
Boxwood can be pruned any time of the year. My chosen method is plucking. This is a term that refers to breaking off branches by hand thereby opening up the plant and allowing more light into its center. Plucking is great for the health and natural beauty of a boxwood.
If you want a natural look, I recommend hand pruning. Note than hand pruning is better for a plant. My favorite pruning shears are Felco No. 2 which is used for branches up to ½ inch diameter. Be sure that your cuts are clean. Use lopping shears for larger branches up to 2” and pole pruners for the difficult-to-reach branches and use curved pruning saws for the larger branches.
Pruning for certain young plants, such as sweet basil, is beneficial as it will encourage the plant to branch. When the terminal bud is removed from a plant, it encourages the side buds to grow and will result in a bushier plant.
Deadheading your plants will encourage their continuous bloom and keep flowers developing. For example, many roses will bloom all summer if the old flowers are removed. Summer is the time to keep your Felco No. 2 pruning shears handy – your garden will prosper!