I wish I could stop by your garden and show you how to prune your flowering shrubs, but that just is not possible. The next best option is to help you understand plant growth and provide a few pruning tips before you pull out your pruners. The most common question I hear, how come my favorite (you can fill in the blanks here)  did not bloom this year? And I always answer with a question: When was the last time you pruned it?

 The biggest misunderstanding about pruning is that all shrubs and trees are pruned when dormant in winter or early spring. Well, to set the record straight, that simply is not true. If you prune flowering shrubs such as lilacs, forsythia, azaleas, and rhododendrons, now  in winter you will be removing the flower buds and be greatly disappointed when they do not bloom this spring. Many – but not all – flowering shrubs whether deciduous or evergreen, bloom on old wood. Old wood are branches that grew the previous year.

 In contrast, some flowering shrubs bloom on the current years growth, this includes: roses, butterfly bush, lavatera, and some – but not all- hydrangeas. Below I have created two lists; flowering shrubs that bloom on old wood and are best pruned just after they flower; and flowering shrubs that bloom on the current seasons growth and are best when dormant. 

 Now that you have a better understanding of when to prune, the next logical question is: How do I prune my flowering shrubs? We have all seen ancient lilac bushes 12 to 15 feet tall with all the blossoms out of reach.  In this situation I favor a pruning technique called thinning; using this technique you can rejuvenate an old leggy flowering shrubs without sacrificing the spring flowers. Thinning is a very simple technique, you prune out 1/3 of the oldest or largest branches from the center of the shrub. Prune out the entire branch, and take it down to 12 inches from the ground. Repeat this for three years and at the end of three years you will have a completely rejuvenated shrub that will not require pruning again for many years. Thinning is also recommended for old blueberry bushes that produce very few berries.

 For fast growing-summer blooming shrubs such as butterfly bush, and lavatera, I use a technique called pollarding. The term pollarding means to encourage new growth. Brace yourself this is a drastic form of pruning – I cut all the branches down to 1 or 2 feet from the ground. These shrubs can be dormant pruned anytime before the leaf buds break open.

 Many shrubs with beautifully colored bark, such as red and yellow twig dogwoods respond well to pollarding by producing vigorous new growth. The new growth will show a more pronounced color than unpruned specimens. Other plants that respond well to pollarding are willows such as the variegated willow ‘Hakuro Nishiki’ and the Arctic blue willow.

 Plants that bloom on current year’s growth and are pruned in late winter or early spring: potentilla, rose of sharon, Japanese spirea, abelia, redtwig dogwood, butterfly bush, lavatera, bluebeard (Caryopteris), hardy fuchsia, hydrangea paniculata (pee gee hydrangea), hydrangea arborescens, (smooth hydrangea), and roses.

 Plants that bloom on old wood and are pruned after they bloom: azalea, barberry, camellia, deutzia, forsythia, lilac, mock orange, kalmia, quince, viburnum, weigela, witch-hazel, rhododendrons, smoke bush, daphne, beauty bush, ninebark, pieris, magnolia, red flowering currant, oakleaf hydrangea, hydrangea macrophylla (mop-head and lace-cap), and fothergillia..