Many of you will have spring flowering shrubs that soon will have finished their flowering for the year. An example of one of the shrubs is the forsythia bush. Over a period of time, forsythia bushes tend to become an overgrown mass of branches that take over a section of the yard. The question always comes up, in the fall, concerning the pruning back of an unruly forsythia bush. Once forsythia is done flowering, it puts out new growth and then sets its flower buds for the following year.
If you prune back a forsythia bush in the fall, you will be removing many of the flower buds that would produce flowers the following spring. The question I then get from people is, “When do I prune back my forsythia bushes?” The answer is that you prune back the forsythia bushes as soon as the shrub is done flowering.
Generally speaking, you can prune back those long canes by about half if you are trying to get the plant back under control. In the case of the forsythia, I have seen cases where the shrub is cut back by three-quarters and it still will spring back and produce flowers the following spring. Once you are done pruning, give the forsythia an application of fertilizer and some water over the weeks following your pruning. If Mother Nature supplies you with rain, you won’t have to do any watering.
As a general rule, all spring flowering shrubs can be pruned back as soon as they are done flowering. This would include rhododendrons, azaleas, spirea, pieris and quince, to name a few. In the case of the rhododendron and the azalea, you can prune back by one-third to one-half, but you must not prune back to the point where there are no leaves on the stem. Pruning back too far will make it hard for the plants to put out enough new growth to set flowers for the following year. Even if you choose to not cut back your rhododendrons and azaleas, they should be fertilized once they are done flowering. In the case of the rhododendrons, the old flower stalks should be pinched back as soon as the plant is done flowering.