08/07/2024
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Sarah Browning, Extension Educator
Buds gradually lose winter hardiness as they develop and can be damaged even before visible flowers are present. Image from Pixabay.com.
Growing fruits in the home orchard takes work and patience. So, when trees fail to bear, despite all the gardener’s work, it’s very disappointing. If your harvest is looking less than ideal this year, there are several reasons trees fail to set fruit and produce a good crop.
Frost Damage
Temperatures below freezing won’t harm fully dormant plants or their flower buds. Buds gradually lose winter hardiness as they develop and can be damaged even before visible flowers are present. Below are the spring temperatures, and the corresponding level of damage to expect, for the most common tree fruits grown in Nebraska. The first pink or white bud stage occurs when color can first be seen in the flower buds.
- Apple, first pink bud stage - 10% kill at 28 F, 90% kill at 24 F
- Tart cherry, first pink bud stage - 10% kill at 28 F, 90% kill at 24 F
- Sweet cherry, first white bud stage - 10% kill at 27 F, 90% kill at 24 F
- European plum, first white bud stage - 10% kill at 26 F, 90% kill at 22 F
- Pear, first white bud stage - 10% kill at 25 F, 90% kill at 19 F
- Peach, first pink bud stage - 10% kill at 25 F, 90% kill at 15 F
To avoid damage from normal spring frosts, select late blooming fruit tree cultivars with winter hardiness to Zone 5.
Locating trees on north facing slopes, which warm up slower in spring, can also help delay flower bud development and minimize spring frost damage.
Excess Tree Vigor
It seems counterintuitive, but fruit trees which are too vigorous put more energy into growing branches and leaves, and less into flower buds. The two main reasons trees would be overly vigorous include 1) over fertilization and 2) over pruning.
If fruit trees are surrounded by turfgrass which is fertilized several times per year, then they are picking up that fertilizer, too. Fruit trees should be fertilized based on either a soil test or an assessment of annual shoot growth. Established, bearing trees should produce 12-18 inches of shoot growth per year. Annual growth on young, nonbearing trees can range from 18-30 inches. Adjust yearly spring fertilization to maintain growth within these ranges.
If overfertilization isn’t the problem, then heavy pruning might be the culprit. Pruning always stimulates new growth and heavy pruning can cause an excess of vegetative growth as the expense of flower production. For more information, visit Pruning Fruit Trees.
Poor Pollination
All flowers must be pollinated for fruit to set. Apples and pears require cross pollination; peaches, nectarines, tart cherries and most plums are self-fruitful. Sweet cherries must be matched with other cultivars which pollinate each other well.
When choosing fruit tree cultivars to plant, research appropriate pollinating cultivars, too. For more information, visit Fruit Cultivars for Home Plantings, University of Missouri.
Other Considerations
Age - Trees must reach maturity before fruit production begins. Generally, the expected age for fruit bearing is as follows. Trees grafted onto dwarfing rootstocks may begin bearing fruits 1-2 years earlier than standard trees.
- Apple and apricot - 2 to 5 years
- Tart cherry - 3 to 5 years
- Peach - 2 to 4 years
- Pear - 4 to 6 years
- Sweet cherry - 4 to 7 years
- Plum - 3 to 6 years
Alternate year bearing - Some fruit trees, especially apples and pears, are susceptible to heavy production one year, followed by few fruits the following year. Fruit thinning during years of heavy production is necessary to prevent the development of a biennial bearing cycle.Branch angles - The large scaffold branches of fruit trees should be developed through selection and pruning, so they grow at wide angles with the main trunk. Ideally, these large branches should form a 60-degree angle, but no more than near 90 degrees. Branch angle affects sunlight penetration into the canopy and hormone development necessary for fruit production. Very upright growing branches produce more foliage than flower buds. Refer to the publication listed above - under the heavy pruning section - for guidelines on pruning and branch adjustments.
Fluctuating winter temperatures - Unusually warm temperatures in January or February, followed by a sudden return to normal or below normal temperatures may also result in flower bud damage. Temperatures in the single digits or below zero can cause a significant level of flower death. Affected trees will not bloom well the following spring.
When your fruit trees aren't producing well, one or more of these issues may be causing the problem. Determining the problems in your home orchard and adjusting your management to address the issues will pay off with bountiful harvests in years to come.
Images
1. Apple flowers require cross pollination by pollen from another apple tree for fruit set to occur. Bees are the primary pollinators of apple trees. Image from Pixabay.com.
2. Fruit trees should be pruned to allow sunlight to enter the tree canopy and selecting for branches with wide trunk-branch angles. Image from Howard F. Schwartz, Colorado State University, Bugwood.org.
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Associated Video
Dormant Fruit Tree Tips
Nebraska Extension Entomologist Jim Kalisch and Extension Plant Diagnostician Kyle Broderick discuss dormant season fruit tree care for diseases and insect pests. Jan 29, 2018.