There are a variety of pruning techniques for maintaining landscape shrubs and bushes. Different pruning techniques are required depending on the type of bush and the time of year as well as the desired effect. Some techniques include renewal pruning, thinning, pinching and shearing.
In general, late winter and early spring just before the plants begin to produce new growth are the best times for pruning bushes. Fall pruning can encourage a flush of new growth that will make the shrub susceptible to winter frost. On the other hand, heavy pruning in spring and early summer removes actively growing shoots and buds, preventing new plant growth. Light pruning can be done at any point during the year, and some techniques, such as pinching, are done after new growth begins.
Renewal pruning is a method used for pruning bushes that grow quickly and produce multiple stems. The renewal pruning technique, also called rejuvenation pruning, requires cutting down 1/3 of the stems to 1 to 2 inches (about 2.5 to 5 cm) tall in late winter or early spring. The oldest stems should be removed, leaving only the new growth. This method works well to encourage older shrubs, or shrubs that have been left unpruned for a long period, to produce new growth.
A variation on the renewal pruning technique for pruning fast-growing shrubs is to cut back the growth each year to the desired shape and size. Once an ideal size for the shrub is determined, all additional growth is pruned off each year. This technique is best used to keep shrubs growing in a dense, neat shape and to prevent them from getting "leggy."
Another method for pruning bushes in thinning. Thinning involves removing select branches to create a more open appearance and to achieve a desired shape. The selected branches are removed at the point where they emerge from an older branch or the primary stem or trunk. This method is best performed before new growth appears in late winter and spring.
Shearing is a pruning method best used when pruning bushes that are grown as hedges. A hedge trimmer is used to cut off all the growth on the outside of the plant. This is used to create formal hedges and topiaries. Shearing is done throughout the growing season whenever the hedge grows 8 inches (about 20 cm) above the desired height and width.
Early in the growing season, gardeners can use a pruning technique called pinching when pruning bushes. As new green shoots emerge from the bases of multi-stem shrubs, they are clipped or pinched off at or slightly above the soil line. This method is similar to renewal pruning, but it is done in spring after new growth begins to emerge.