Q:
Can you tell me how to prune a ‘Mt. Fuji’ cherry tree (Prunus serrulata ‘Mt. Fuji’)? Mine is about 4 years old, more than 5 feet tall, and showing pronounced horizontal branching.
Sam Inaba, College Place, WA
'Mt. Fuji' cherry trees have a strong horizontal branching habit. Prune them in late spring, after flowering.
Photo/Illustration: Jennifer Blume
A:
Scott Loosley, garden consultant and arborist in Santa Cruz, California, replies: Ornamental cherries are great choices for the garden, providing unique branching characteristics in addition to beautiful blossoms. The ‘Mt. Fuji’ cherry tree, in particular, displays strong horizontal branching. With age, it will reach up to 20 feet in height and have an even wider spread.
Flowering cherry trees generally don’t require much pruning. Flowers are produced on the previous season’s growth, so heavy winter pruning is not advised, as you’ll cut off all the flowers. The best time to prune cherry trees is in late spring or early summer, after flowering has finished and the tree has leafed out.
While your tree is young, you have the best opportunity to develop good branching habits with sound structural characteristics. Take a good look at your tree before you start pruning. Have an idea of the eventual shape you’d like to achieve before you start to cut. And in your mind, visualize the dimensions of a mature tree. Branches that are a finger-width in diameter on a young tree will become 3 or 4 inches in diameter on a mature specimen. So when pruning a young tree, take into account the eventual size of mature branches.
After you’ve put some thought into the process, your first pruning considerations should be the removal of dead, diseased, and damaged wood—commonly called the 3Ds. The next step is to eliminate crossing branches that will rub and create wounds.
Once these tasks have been accomplished, you can select permanent scaffold branches. These are the tree’s main side branches. Scaffold branches should be arranged in a spiral around the tree’s trunk and spaced to allow for growth, 6 to 12 inches apart. Prune out limbs that originate from the outer area of the canopy and cross back through the center of the tree. Keep branches that create an open habit, growing from the center of the canopy outward. Finally, low-growing limbs should be pruned to prevent them from touching the ground.
This early training process can take five years or more, so be patient. Once your tree is mature, there should be little need for heavy pruning, except for eliminating the 3Ds and crossing branches.
