When working with an older plant that has not had regular pruning, plan to prune the plant gradually over a three-year period. The first year, start by pruning out one-third of the oldest, woodiest stems. Repeat the process for the next two years. At the end of three years the plant will be slightly shorter, fuller and have more flowers.
Renovation of a shrub involves cutting down the entire shrub to within several inches of the soil. Renovation removes all the old, woody branches that are susceptible to boring insect damage. Renovation allows the plant to regrow in its natural form, and forces the plant to send out new, vigorous growth that is often healthier than the older growth that was removed.
However, renovation usually results in a lack of heavy flowering for a season while the plant regrows. Renovation pruning can be done during the dormant period. Some shrubs, like evergreens, will not tolerate renovation pruning, so be sure to do a little research before cutting.
Ray Ridlen is an agriculture/horticulture educator for the Oklahoma County Extension Service. For more information, call 713-1125.