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KEEP SPRING FLOWERING SHRUBS BLOOMING WITH PRUNING

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published – MAY16, 2014

KEEP SPRING FLOWERING SHRUBS BLOOMING WITH PRUNING

Last weekend I took advantage of the nice weather to prune my forsythia that was seriously crowding nearby plants. I hadn’t pruned it much for the last two years and it was becoming unruly. It put on a beautiful show of blooms this spring, but I knew that if I didn’t get in there and remove some of the old wood it probably would not have as many flowers next year.

My approach was to go in and remove one-third to one-fourth of the older (thickest stems with side shoots) stems down to the ground. A healthy forsythia is a vigorous shrub that sends up new stems each year that bloom the following spring. Removal of the oldest stems should be done right after flowering because the flower buds for next spring are formed on the new wood by early summer. Pruning later in the season or in winter will reduce the potential flower display next spring.

Occasionally, one or more forsythia stems grow rather long, giving the shrub a rangy, wild appearance. If not an older stem that should be removed, I cut the stem back to a side branch to shorten it.

A weigela was one of the plants being crowded by the forsythia. I planted it in early summer two years ago and initially it benefitted from the shade the forsythia provided, but now it needs more light. I also have two mature weigela shrubs elsewhere in my landscape.

One of these weigelas is ‘Wine and Roses’ with dark burgundy leaves and dark pink flowers. It has prospered in its spot but now it has become a bit bedraggled and there are a number of dead twigs and branches throughout. Since weigelas are prone to winter dieback, this may have been caused by the sudden cold snap last fall. The dieback could also be related to the increasing amount of shade provided by two trees on that side of the yard. Weigelas do best in full sun and will become straggly if located in shade or crowded by other plants.

Perhaps I should just remove it and plant a more shade tolerant shrub, but I think I will see if I can revitalize it first. As soon as it is done blooming, I am going to prune out the thickest, oldest stems along with any of the dead branches and twigs. To shape it up a bit, I plan to selectively prune back any overly long stems to a side branch, being sure not to remove more than one-third of the stem.

Most other multi-stemmed spring-flowering deciduous shrubs are also pruned right after flowering. This is because they too flower on wood produced the previous growing season. These shrubs include forsythia, weigela, lilac, viburnum, honeysuckle, mock orange, Nanking cherry, flowering quince, white-flowered spireas, beautybush, and deutzia. Like forsythia and weigela, one-fourth to one-third of the oldest wood should be removed back to the ground each year.

As part of your pruning tasks, you should also “deadhead” or snip off the spent flowers or seed-heads from the stems you don’t remove. This will give the shrub a tidier appearance and allow its energy to go into plant growth rather than seed development.

It really does not take much time or effort to keep spring flowering shrubs looking their best. Give it a try. Sometime soon we can chat about pruning summer flowering shrubs.

Published: 5/16/2014 11:48 AM

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