By Nadie VanZandt, extension master gardener, University of Vermont
Has your apple tree looked poorly all summer and produced little or no fruit this fall?
Although the summer’s abundant rainfall may have caused stress due to overwatering, there are other reasons why your apple tree failed to thrive. These include nutrient deficiency, an unfavorable growing environment, pests, diseases and the age of the tree.
In ideal growing conditions and when properly maintained, apple trees may remain productive for over 50 years. The bearing age — time from planting to bearing fruit — depends on the species, cultivar and whether the tree is grown on dwarf or standard-size rootstock. The average bearing age varies from three years for dwarf trees to eight to 10 for standard trees.
Apple trees prefer full, direct sunlight, which means at least six hours of daily sunlight. They require a site with good drainage and soil amended with the highest-quality compost to improve aeration and reduce compaction.
Proper feeding, maintenance and pruning go a long way in keeping trees healthy and helping them withstand attack from pests or diseases. Trees also benefit from strategic pruning in late winter or early spring to open the canopy to air and light and to reduce apple scab and other foliar fungal diseases.
Mulching and weeding under the canopy facilitates access to nutrients. Keeping the base of the tree weed-free will minimize boring pests and feeding by small vertebrates. Protecting the base with hardware cloth or mouse guards before winter will help prevent rabbit or vole damage in years with heavy snow cover.
Low fruit production may not necessarily indicate a serious problem since apple trees normally bear heavily one year and less the following, known as biennial bearing. Thinning the trees after fruit is set will help keep fruit loads more consistent.
Assuming your tree’s poor health is not due to pests or diseases, it can be rescued. First, check to see if your tree is alive. Use sharp pruners to cut a small branch. Green tissue indicates that the tree is alive and worth putting in effort to improve vigor.
However, your tree may not be worth saving if it has other issues, such as large areas of dead wood, large sections of damaged bark, weeping wounds, large branches with internal rot, cankerous growth or the presence of pests or diseases. Leaf drop, shoot dieback, yellow or brown leaves in summer and small or brown fruit could signal fungal or bacterial diseases or other stress in the trees.
Removing an established apple tree is a tough decision, especially if it has sentimental value, provides structure to your garden or has produced delicious fruit in the past. But a weak tree will attract pests and diseases, further deteriorating its health. If you are not sure whether the tree should be removed, seek professional advice from a local arborist.
If you decide on removal, fall is a good time for this task. While removing a young dwarf apple tree might be manageable on your own, removing larger trees requires hiring a tree removal service that also will grind the stump and get rid of large roots.
Planting a new apple tree at the same location depends on whether the old tree was diseased. Pathogens that caused the old tree to die can survive in the soil, as well as in dead or dormant roots. This contamination could cause a condition called replant disease. If so, plant the new tree a few feet away from the original location.
Assuming the site is disease-free, you can replant a new apple tree at the same site. First, move the mulch created from grinding the stump to your compost pile. Next, replace the soil in the old planting site with quality soil, preferably from a non-orchard site, to prevent transferring soil pathogens from other fruit trees. Let the prepared site rest over winter.
When choosing the perfect apple tree to plant next spring, look for cultivars resistant to common fungal diseases, such as apple scab and cedar apple rust, suitable for your U.S. Dept. of Agriculture plant hardiness zone (planthardiness.ars.usda.gov).