Several varieties of basket willow (Salix purpurea or S. purpurea)--a perennial shrub--exist, but all varieties have the drooping branches and delicate leaves that make willows an elegant addition to a landscape garden. S. purpurea can be pruned down almost to the ground at the start of spring because, like most willows, its trunks or stalks (commonly called "rods") can regenerate and grow from 4 to 10 feet in one season. Pruning provides attractive, brightly-colored new growth. S. purpurea rods are particularly popular for basket weaving.
When to Prune
Nurseries recommend pruning willows, regardless of method, anytime in late winter to early spring, when buds may have appeared on rods but are still immature. If you remove growth from S. purpurea during the summer months, your willow may not have time to regenerate fully before the end of the growing season, especially if you live in a region where summers are dry.
Pruning with the coppice method encourages new growth. To do so: Prune your S. purpurea rods down to 1-2 inches off the ground, or to the point where their growth began the previous year. This extreme pruning is called coppicing; it encourages new rods to sprout from the base of the shrub, creating a brushy thicket for privacy.
When pruning, make a clean, level cut straight across the branch or rod. Avoid splintering or splitting branches because that damages all plant cells along the injury site. You can start coppicing after the very first season of growth.
If you want a denser, round head of branches, instead of the multiple stalks created by coppicing, try the Pollard method of pruning. Begin in the first winter season after planting. During that winter, while the plant is still dormant, choose the strongest rod and cut it back to approximately 3 feet. Cut off all the other rods at the base. Go back to coppicing---cutting all rods down to one or two inches---in the following winter.
S. purpurea should have an attractive shape and healthy, vigorous growth after you coppice for at least two growing seasons. At that point, stop pruning if you want a taller shrub. The willow will grow to its full height, but the height depends on the variety. For instance, S. purpurea 'Nana' is generally less than 5 feet high, while Salix purpurea 'Streamco' can reach 10 feet.