Alternate (Biennial) Bearing: Why It Happens and How to Break the Cycle

What alternate bearing is and why it happens

The pattern is a two-year cycle: a large crop followed by a small one, then back again. Iowa State explains that during a heavy crop most of the tree's energy goes into fruit development, leaving little for flower initiation, so few flower buds form for the following year, which produces the off year. The tree is not sick; it is out of balance.

There is also a hormonal brake. Utah State notes that seeds developing in the fruit produce plant hormones that prevent nearby flower-bud development, and that large crops deplete the tree's carbohydrate reserves. So a single very heavy on year suppresses the next year's bloom both by exhausting reserves and by hormonally shutting down flower-bud formation. A spring frost that wipes out one year's bloom, leaving the tree to over-set the next year, can also trigger the cycle.

Which trees do it

Alternate bearing shows up across tree fruits but is especially associated with pome fruits. Iowa State notes it occurs in almost all tree fruits but is particularly common in apple and pear, and it also affects some plums. Certain cultivars are far more prone than others, several apple varieties, including Honeycrisp and Golden Delicious, are known for biennial bearing, while others crop more evenly.

Knowing your cultivar's tendency helps you plan. A biennial-prone variety benefits most from disciplined annual thinning, whereas a naturally even-bearing tree needs less intervention. Either way, the mechanism is the same, so the remedy is the same: manage crop load so the tree never carries such a heavy year that it shuts down the next one.

Breaking the cycle with early thinning

Thin in the on year, and thin early. Iowa State advises hand-thinning within about six weeks of full bloom, and Utah State places the optimum in the first two to three weeks after bloom, because thinning after that window will not improve fruit size or next year's flower-bud development, the tree has already committed. The goal is to reduce the heavy set before those developing seeds suppress next year's buds.

How much to remove: space the remaining apples roughly six to ten inches apart, thinning to about one fruit per cluster (Utah frames it as leaving about one fruit per few spurs) and keeping the largest, undamaged fruit. Early thinning does triple duty, it restores return bloom the following spring, improves the size and quality of the fruit you keep, and prevents limbs from breaking under an over-heavy load. Combine it with consistent watering and feeding, and see how and when to thin fruit for the mechanics and the broader backyard fruit tree spray schedule for where thinning sits in the season.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Iowa State University Extension - Alternate Bearing, Fruit Drop, and Hand Thinning of Tree Fruits — Alternate or biennial bearing is a two-year cycle of a large crop followed by a small one, occurring in almost all tree fruits but particularly apple and pear, because heavy fruiting leaves little energy for flower initiation; hand thinning within six weeks of full bloom, spacing apples about six to ten inches apart, prevents alternate bearing and improves fruit size.
• Utah State University Extension - Fruit Production FAQ (Small Acreage) — Seeds developing in fruit produce hormones that prevent nearby flower-bud development and large crops deplete carbohydrate reserves, causing alternate bearing in apples and pears; the optimum thinning timing is the first two to three weeks after bloom, leaving roughly one fruit per three spurs, since later thinning will not improve flower-bud development for the following year.

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