By Julie Barnes
Late winter or early spring is maybe opportune to give various plants a good prune before they wake up from dormancy. Pruning cuts made at this time of year tend to heal faster, disease and insect problems are minimal, and a tree’s real form is easier to perceive when leaves are missing.
This gardening task of removing plant parts from deadheading to branch removal can be quite overwhelming to all of us. Reasons to prune include:
Cutting off dead, diseased, or damaged stems to maintain plant health
shaping and thinning to control plant size
cutting back to increase flowering or fruiting
rejuvenate an old scraggly plant into healthy new growth.
For shrubs, especially, you must become familiar with the 2 different groups to do this job properly. Some bloom on old wood where their buds were formed on the previous season’s growth. Others bloom on new wood that is produced during the current season.
Sometimes, determining whether a plant blooms on old or new wood can be a challenge. For almost all woody plants a simple rule of thumb to follow is: Plants that flower before June flourish from buds that matured on old wood. Here, the proper time for pruning is immediately after they finish blossoming which is basically like “deadheading “on a large scale. Something to help you remember is: “prune comes after the bloom.” As soon as the flowers fade, all the stems carrying the dead flowers can be cut back. Vigorous summertime growth then produces the flower buds for the next year. Pruning this group of plants in winter or early spring will cause them to either bloom sparsely or not at all.
Exceptions to pruning after spring flowering are plants that will bear decorative autumn fruits. These may be lightly pruned after fruits have faded in late fall or in very early spring.
On the other hand, shrubs that flower on new wood are best pruned in late winter, or very early spring before new growth begins. Cutting back encourages the development of strong shoots that will produce fruits or flowers far more reliable, prolific and often larger than those found on plants not cut back. Here are some old and new wood examples:
Trees or shrubs to purne after bloom
Beautybush (Kolkwitzia amabills)
Azalea & Rhododendron (Rhododendron spp.)
Bigleaf hydrangea (Hydrangea macrophylla)
Lilac (Syringa vulgaris)
Fosythia (Forsythia spp.)
Ninebark (Physocapus opulifollus)
Viburnum (Vibrunum spp.)
Weigelas (Weigela spp.)
Lily of the Valley Shrub (Pieris spp.)
Mountain Laurel (Kalmia Latfolia)
Bridal Wreath Spirea (Spirea x Vanhouetti)
Prune in late winter or early spring
Bush cinquefoil (Potentilla fruticosa)
Butterfly bush (Buddleia davidii)
Blue-mist shrub (Caryopteris spp.)
Hydrangea Peegee (H. paniculata Grandiflora)
Hydrangea Annebelle (Hydrangea aboresens)
Japanese spirea (Spiraea japonica)
Rose of Sharon (Hibiscus syriacus)
Smoke bush (Cotinus coggygria)
St John's wort (Hypericum spp.)
Clethra (Clethra spp.)
Bush Rose (Rosa spp.)
To all of us, the large showy blossoms make Hydrangea beautiful specimen plants in the garden. So, it can be a great disappointment when hydrangeas fail to bloom for a season. From the lists that I have provided, you can see that distinct types of hydrangea are pruned either after bloom or in late winter or early spring. A main reason why a Hydrangea fails to bloom is because it was pruned at the wrong time. This plant is an example of why it is important to know what kind of plant you have. So, know when to prune to avoid the gloom.