Have you heard of Egyptian apple pie? It’s the type mummy used to make.
Apples are the most common homegrown fruit in Northern regions. Most apple tree owners know they’re supposed to prune their trees, but it’s not always clear how to do it.
Apple tree pruning isn’t as complicated as it might seem, once we understand what twigs and branches to remove. By following a few simple pruning guidelines, apple trees become healthier and more productive.
Tools needed include handheld pruning shears for cutting pencil-diameter twigs and branches, and a long-handled lopper for branches an inch in diameter. For larger-diameter branches, a pruning saw is used.
Why prune an apple tree? If left to their own devices, most apple trees grow into large, globe-shaped trees with the best fruit forming on the tree’s outer perimeter, high above convenient apple-picking height.
Besides controlling size and height, pruning promotes higher production of quality fruit. An unpruned apple tree becomes a tangle of crisscrossing branches that sunlight can’t penetrate. Pruning thins out the canopy, allowing more sunshine to enter, resulting in more flowers and more apples.
Pruning also levels out yearly fruit crops, reducing the tendency of some apple types to have boom-or-bust apple harvest cycles, where trees bear heavily one year, followed by no apples the next, referred to as biennial bearing.
When is the best time of year to prune apple trees? The traditionally recommended time is from about March through early April, after winter’s coldest weather is likely past, and when they’re still dormant before new growth begins.
Chris Flynn / The Forum
If fire blight bacterial disease has been a past problem on an apple tree, then pruning during late winter’s full dormancy is still recommended. Fire blight is most easily recognized by outer twig growth that curves in the shape of a “shepherd’s crook” with brown leaves that look as though they’ve been scorched by fire.
When fire blight isn’t present, though, there’s a good case to be made for readjusting our traditional pruning time.
Jim Walla, retired NDSU plant pathologist, now with Northern Tree Specialties, is a leading fruit tree authority, and he favors delaying apple tree pruning until the time when the flower buds start swelling and through the start of leaf emergence.
As Walla indicates, the risk of black rot canker fungus, which is by far the most damaging disease of apples in our area, is reduced by delaying pruning until trees have begun growth. This helps pruning cuts seal more rapidly, leaving less tissue open to invasion by the black rot fungus.
Walla’s observations about delayed pruning are well worth noting. I’m following his recommendations on our own apple trees, because each year I observe many trees seriously damaged by black rot canker disease.
Where do we start cutting? Begin by imagining the ideal, well-pruned apple tree. The shape favored by research is a pyramidal Christmas tree shape, with the lowest branches being the widest, becoming narrower as you go up.
Pruned to this shape, all branches receive greater sunshine, which encourages more flowers and fruit lower on the tree. The shape is called a “central leader system” in which a single central trunk runs the height of the tree, with strong side branches, called “scaffold” branches, radiating outward.
On young trees, if there’s more than one central leader, remove one to eliminate “V” branching at the top of the tree. Prune into a pyramidal shape with the lowest branches being widest, and shorten progressively as you move up. Always cut to a side bud or branch, never leaving empty stubs.
If an apple tree is a little older, around 5 to 10 years old, and is currently a round globe, prune it into the pyramid shape described. Start with the lowest branches, making them the widest, and move up the tree in stair-step fashion until the top is the narrowest point.
Branches along the central trunk are often too close together on younger trees. The main horizontal scaffold branches should be spaced 12 to 24 inches apart along the trunk. Remove excess branches back to the trunk, pruning just outside the raised “collar” where the branch arises from the trunk.
Chris Flynn / The Forum
If your apple tree is older, overgrown and has never been pruned, reshape it gradually over several years. Remove about one-fourth of the tree’s height each year for four years, attempting to get the tree down to about 12 feet high.
After shaping the tree and controlling its height, prune out crisscrossing branches and branches pointing backward into the tree, so branches radiate outward.
Remove upward-pointing shoots, called watersprouts, from main branches. Remove sucker growth from the tree’s base, and any dead wood.
Pruning paints and sealers are not recommended, as research has shown they can impede a tree’s natural ability to seal pruning wounds.
