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Pruning of Overgrown Shrubs

Source: NDSU Extension Service Horticulturist

Tall, overgrown non-evergreen shrubs may be given a new lease on life through proper pruning. Renewal pruning involves selective removal of the oldest, heaviest canes as close to the ground as possible. Because pruning usually results in the stimulation of new shoots just below the pruning cuts, all subsequent shoot growth takes place at the base of the shrub. If top pruning is practiced, the natural form of the shrub is destroyed. All new shoot growth will arise just below these cuts resulting in a butch-haircut appearance. New shoots usually do not arise from near ground level with top pruning.

Proper timing of renewal pruning is important. Severely overgrown shrubs will respond best to pruning done in early spring, before new growth begins. For spring-flowering shrubs, prune immediately after flowers have faded. This would include shrubs like spirea, mockorange, lilac, doubleflowering plum, and others that bloom before July. Pruning at this time will not sacrifice part of the flower display and will insure maximum flower bud development on the remaining branches for the following year. Summer-blooming shrubs should be pruned in early spring.

The renewal pruning of badly neglected, overgrown and "leggy" shrubs may have to be a gradual process. If there are few, if any, young canes arising from the ground, only 1/3 to 1/2 or the old, heavy canes should be removed at one time to allow for the development of new shoots. The renewal pruning process is thereby accomplished over a period of two or three years.

It is a good practice to regularly remove two to three of the oldest canes from shrubs that have reached their mature size. Shrubs maintained in this manner will always be attractive, vigorous and healthy. Tools needed for renewal pruning are a long-handled loping shears and a pointed, curved-blade pruning saw.

If you have further questions, please contact your county office of the NDSU Extension Service.

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