How to Prune Pacific Ninebark

Enhancing Growth Habit

• Pruning keeps the long, lanky stems of Pacific ninebark looking tidy and develops a more dense growth habit as the shrub matures. In late winter, before the leaves come out, cut back about one-third of the previous season's growth to stimulate a more compact growth habit. At the same time, prune some of the oldest stems completely, cutting them off flush with the main trunk near the base of the plant where they originate. This keeps the shrub looking open and fresh.

Maintaining Size

• Pacific ninebark grows quickly to 15 feet tall and wide if left unpruned. This is rather large for most home landscapes, but it's easy to keep them pruned to 6 or 8 feet, if desired. At the end of summer, after all the flowers have faded, cut back the shrub to the intended height. During spring and through summer, pendulous stems will grow from the top of the cuts in a graceful fashion. Continue to cut these back to the same point at the end of each growing season to maintain the height.

Training to a Tree

• Pacific ninebark grows large enough that it can be trained into a small tree. Start when the the shrub is first planted by choosing one vigorous, vertical stem as the main trunk and tying it firmly to a stake extending 4 feet from the ground, and set at least 1 foot into the soil. Remove all the lower branches, cutting them flush to the main trunk or all the way to the soil level if they are growing from the ground. Once the stem that was selected for the trunk has reached about 5 feet in height, cut it back to the height of the stake -- this will stimulate branching at 3-1/2 to 4 feet from the ground. Continue to remove any lower branches that appear.

Other Considerations

• Avoid pruning Pacific ninebark in the summer months when it is flowering. When cutting back branches for shaping or to control height, cut them to slightly different lengths. This gives develops a tidy, but natural look in the plants, as opposed to the structured appearance of a formal hedge, which is not an appealing form for Pacific nine bark. Finally, to prevent the spread of disease, sanitize all pruning equipment when working with ninebark. Dip the cutting blades in rubbing alcohol or a 10 percent bleach solution before pruning each shrub.