Why Apple Trees Produce Fruit Every Other Year (and How to Even It Out)

Short Answer

A heavy apple crop uses up the tree's energy and sends hormone signals that stop it from setting flower buds for next year. The tree gets a light bloom the following spring, then recovers and floods with blossoms the year after. Growers call this biennial bearing (fruiting heavily one year and lightly the next).

You can usually break the cycle by thinning young fruit early in a heavy year. Plan on two or three seasons before the tree settles down.

Why It Happens

Here is the part that surprises most people: an apple tree decides next year's crop while this year's apples are still small and green. Flower buds for next spring form in early to midsummer, only a few weeks after bloom.

If the tree is carrying a huge load at that moment, two things go wrong. The developing seeds release plant hormones that discourage flower bud formation, and the fruit hogs the sugars the buds need. Fewer buds form, so next spring's bloom is thin.

Then the pattern flips. A tree with a light crop has plenty of energy and puts out buds everywhere, which sets up a flood of blossoms the next spring. That heavy crop produces small apples and fewer buds, and the swing locks in.

Weather often starts the cycle. A late spring freeze that kills most blossoms leaves the tree nearly empty, and the following year it overloads. Variety matters too. Honeycrisp and Fuji have a reputation for swinging hard, while other varieties barely show it. Young trees usually behave until they carry their first really big crop.

What To Do (Remove More Fruit Than Feels Right)

Thin in the heavy year, the one where the tree is covered in blossoms. Wait until the young apples (called fruitlets) are roughly the size of a dime to a quarter. That usually lands three to five weeks after petals fall.

Timing follows bloom, not the calendar. In warmer zones (roughly USDA zones 6 to 8), thinning often wraps up in May. In colder zones (3 to 5), bloom comes later, so thinning often slides into June.

Here is the routine:

1. Pinch off extra fruitlets so each cluster keeps one apple, two at most on a large, healthy branch.
2. Leave about 6 to 8 inches between the apples you keep.
3. Keep the best-shaped, healthiest fruitlet in each cluster and remove any that are lopsided, scarred, or chewed.
4. Snip or pinch the stem instead of pulling. Yanking can tear off the spur (the short, stubby twig that carries fruit year after year).

This works because fewer apples mean fewer seeds, which means less of the hormone that blocks buds. The tree can build next year's flowers while it ripens this year's crop.

In the light year, mostly leave the tree alone. There is little to thin, and the tree is already setting plenty of buds. Hold back on extra nitrogen fertilizer too. Heavy feeding pushes leafy growth instead of fruit buds.

What To Watch For

Expect a gradual reset. The first season you thin, the tree may still bloom lightly because some buds were already set. A medium crop the following year is a good sign.

You will pick fewer apples in the big year, but they tend to be larger and better colored. Many growers also find the off year improves, which is the real payoff.

The most common mistakes:

• Thinning too late. The size benefit remains, but the reset is mostly gone.
• Thinning too timidly. Leaving three or four apples per cluster barely changes the hormone load.
• Heavy winter pruning to "fix" it. This triggers vigorous leafy shoots with few flower buds.

In winter, you can check your progress. On the spurs, plump, rounded buds are usually flower buds, and slim, pointed ones are leaf buds. Lots of fat buds on a tree that just carried a big crop is a good sign.

Step in right away if branches are bowing or cracking under the load, no matter what the calendar says. Props or emergency thinning beat a split limb.

And if your tree never flowers well in any year, alternate bearing is probably not the cause. Look at shade, pollination, tree age, and nitrogen instead.