Prune corkscrew willow (Salix matsudana) when it's young. This tree has a wild and irregular growth habit that needs early training for good health later in life. Like most willows, corkscrew willow has weak, brittle wood that is prone to breaking under its own weight as the tree matures. Unlike most willows, this tree has vertically growing, twisted and contorted branches that give it an interesting look after leaves fall in autumn.
Prune corkscrew willow in early winter when sap is running the slowest. This tree is prone to insects and fungus, so it's best to trim them when pests are least active.
Dip pruning shear blades in boiling water for 30 seconds, then wipe them dry with a clean towel. This will prevent fungus, bacteria and insect eggs from entering pruning wounds.
Look for dead or storm-damaged wood on corkscrew willow. Pay particular attention to branch crotches, where the branch meets the trunk. If you see splitting or cracking, the branch must go.
Set the blades of pruning shears at 45 degrees, cutting down and out, leaving a 1/2-inch stub that will drain moisture instead of collecting it and causing rot.
Trim away branches and twigs that are crossing and rubbing. Bark injury from rubbing will attract insects and disease. It won't be possible to cut every crossing limb on a corkscrew willow. Cut only about 1/3 of them in any given year to keep the tree as healthy as possible.
Bag and dispose of prunings in yard waste bags, especially if your corkscrew willow has disease or insect pests. Rake up twigs and leaf litter throughout the year to eliminate the environment that helps problems develop.
Always clean pruning equipment after use, especially if you've been working on a problem tree.
Don't plant corkscrew, or any type of willow, near buried water or sewer lines. Willows have large, aggressive root systems that can crush clay pipes.