By Richard Jauron
Extension Horticulturist
With spring just around the corner, fruit tree owners should start to think about the care of their trees and this year’s fruit crop. The key to a good fruit set is to provide conditions favorable for flower bud formation, survival and pollination.
Horticulturists with Iowa State University Extension and Outreach share tips and practices that improve a tree’s ability to begin and continue to bear fruit. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or at hortline@iastate.edu.
When should I prune my fruit trees?
Late February to early April is the best time to prune fruit trees in Iowa. Fruit trees should be pruned before they begin to leaf out in spring. Summer pruning of fruit trees is generally not recommended. However, water sprouts, rapidly growing shoots that often develop just below a pruning cut, can be removed in June or July.
How often should fruit trees be pruned?
Fruit trees should be pruned on an annual basis. Annual pruning of young (non-bearing) fruit trees develops a strong framework and desirable tree shape. Annual pruning of bearing trees maintains tree vigor, maximizes fruit yields, and improves fruit quality. Young trees require light annual pruning. Bearing trees require light to moderate annual pruning. Insufficient pruning of bearing trees may result in small, poorly colored fruit with a low sugar content and mediocre favor. Excessive pruning of bearing trees weakens trees and results in vigorous shoot growth with little or no flower bud formation for the following year’s crop.
When should I apply a dormant oil spray to my fruit trees?
Dormant oil sprays are highly refined petroleum products that are mixed with water and applied to trees and shrubs to control aphids, spider mites, and scale. Dormant oils destroy pests by suffocating them. When applied properly, the thin film of oil plugs the spiracles or pores through which the mite or insect breathes.
Proper timing is critical when using dormant oil sprays. Dormant oils should be applied in late March or early April in Iowa before the trees show signs of breaking dormancy (before bud break). Dormant oils applied in February or early March are not effective as insects are not actively respiring at this time and, therefore, not vulnerable to the oil’s suffocating effects. Dormant oil sprays should be applied as close to bud break as possible.
Rabbits have gnawed on the bark of my fruit trees. Have they been seriously damaged?
During the winter months when food is scare, rabbits often gnaw on the trunks of young, thin-barked, trees. Trees that have had their bark removed completely around their trunks have been girdled and essentially destroyed. Wrapping the trunks or applying pruning paint to the damaged areas will not save the trees. Most girdled trees will eventually sucker from their base. However, since most fruit trees are propagated by grafting, suckers which originate from the rootstock will not produce a desirable tree.