The Best Time to Prune a Dwarf Katsura Tree

Identification

• Katsura is a deciduous tree that grows with both a single- or multitrunked habit, depending on the specimen and the pruning it has received. Although the species tree can reach over a hundred feet in the wild and usually grows to between 40 and 60 feet under cultivation, “Heronswood Globe” is a small, dwarf form that tops out around 15 feet in the first 10 years. Eventually it may reach heights of 20 feet, and is hardy in U.S. Department of Agriculture plant hardiness zones 4 through 8. “Ruby” is another dwarf form, growing to around 30 feet and hardy to USDA zone 4 and above as well.

Maintenance Pruning

• If you care about fruits and flowers, the best time to prune spring-flowering trees is after they bloom. Because spring bloomers such as katsura form their flower buds on old wood, late winter pruning risks removing buds. Most people do not care about the small, nonshowy flowers. The pods, however, which persist on female plants throughout the winter, have some decorative value, so if you care about them, wait until after the bloom to prune. If you don’t mind losing them, prune in late winter, just before new growth starts. At this time you should thin the canopy to allow light in and prune for shape.

Disease Pruning

• Any time the plant exhibits signs of disease, you should prune. Remove all dead, damaged, broken or infested branches several inches below the last visible symptom. Open wounds are one of the best ways to transmit disease, so disinfect your pruning shears by rubbing the blades with isopropyl alcohol both before and after you prune. You should also clean the blade between each cut. Otherwise you risk spreading disease from one part of the tree to another, or to different plants.

Pruning Techniques

• Feel free to prune lateral branches, but unless there is a problem with it, never cut back the tree’s leader, or central trunk. This is called topping and can harm the tree. Instead, prune with an eye to the tree’s natural form, allowing it to develop an open, spreading canopy that will promote movement of light and air, which will in turn decrease the chances of the tree contracting diseases. Always prune back to a bud or side branch, or flush against the tree’s trunk, so that you make cuts at a natural juncture.