You can prune an apple tree any time of year without hurting it, but late winter is best. The worst of the cold weather is past, so you won’t be subjecting the fresh cuts to severe icing, but you will still be able to influence the tree’s spring growth.
There are several objectives to pruning an apple tree, says Pat Patterson, Oregon State University Extension Service master gardener:
- Controlling the height of the tree so most of the fruit doesn’t grow out of reach.
- Developing good limb structure for strength, fruit production and the general health of the tree.
- Encouraging a plentiful supply of new limbs, which will begin to bear fruit their second year.
- Ridding the tree of damaged or diseased growth.
The overall size of the tree depends primarily on its rootstock and innate vigor. Most apple trees are grafted onto dwarf or semidwarf rootstock. Take care when you plant an apple tree not to bury the graft, where the fruiting stock joins the rootstock. This ensures the fruiting stock will not begin to produce its own roots, and the tree will keep its dwarf or semidwarf height.
Monitor the height of your tree to ensure it doesn’t outgrow the spot you’ve picked for it. Once it’s as high as you want it to be, prune the central leader—the main upright limb—back to a lateral branch. Monitor the height annually.
“Don’t expect a new young tree to start bearing well until probably its fourth or fifth year,” Pat says. “In the long run, the tree will do better to put its energy into root and limb growth rather than fruit for those first few years. Concentrate your pruning to produce a strong tree during that period.”
Inspect your tree for limbs that branch from the central leader either too sharply upward, forming an acute angle, or at too wide an angle. Acute angles tend to trap bark as they grow and can lead to splitting.
Branches that grow at too great an angle from the vertical tend to be weaker. They also encourage water sprouts—the unproductive upright shoots that need to be pruned off midsummer every year. The ideal angle between the central leader and lateral branches is about 60 degrees.
In general, encourage branches to grow toward the outside of the tree and eliminate those that grow toward the center or cross other branches. You want air and light to penetrate the foliage to the center of the tree as much as possible.
“Different kinds of apple trees have different ways of setting fruit buds,” Pat says. “Most modern apples are spur-bearing. Many older varieties are tip-bearing. This is obviously important for how we prune the tree so as not to cut off the fruiting wood.”
Spur-bearing trees grow fruit on small thornlike shoots called spurs, which grow evenly along the main branches. Tip-bearing trees produce fruit on the tips of branches instead of along the branch.
If you’re in doubt but know the name of your tree, ask at your local nursery or look it up in a good gardening book or online.
Once your tree has matured and begins to produce fruit, expect new branches to bear their best for several years—perhaps three to five years—and then taper off. Remove older branches that have begun to produce less to encourage new ones.
Summer is a good time to remove older branches, when it is obvious which branches produce best and which should be pruned. Summer pruning also allows you to get rid of branches that show signs of damage or disease as soon as you spot them.