URBANA, Ill. — Apple trees have been a common landscape feature throughout human history. As humans become more urban-dwelling, apple trees are finding new homes in cosmopolitan landscapes far from familiar orchards.
“Urban apple trees are usually dwarf varieties or columnar apple trees, which are fairly new in the horticulture trade,” said Austin Little, University of Illinois Extension horticulture educator.
Both dwarf apple tree and columnar-shaped trees grow 10- to 15-feet tall. Columnar cultivars have very narrow branching for the limited space in urban settings.
Many varieties of apple trees are self-unfruitful, which means they need pollen from another tree, provided by pollinators or the wind, to grow fruit.
In urban environments, there are often plenty of crab apple trees or other apple trees around. However, homeowners can help pollination rates by planting crab apple trees, other compatible apple varieties, or even Quince, nearby.
Apple trees need about 1 pound of nitrogen a year once they start bearing fruit, which can take up to four years. Many yards have enough nutrients available for the first few years of growth. If a yard is regularly fertilized, this usually provides all the nitrogen the tree needs.
“The best way to find out if you need fertilizer is to get a soil test,” Little said.
Mulching around the base of the tree with an organic material also helps add nutrients, as well as retain moisture, suppress weeds and improve soil microbe health. Apply partially decomposed hardwood mulch at about 5-inches deep, or conditioned compost at about 3 to 4 inches.
Keep mulch about 6 inches away from the base of the trunk to deter rodent damage. Mulch should be replenished once a year, Little said.
Fire blight is one of the most common bacterial pathogens affecting home apple trees. The best way to control it is to remove any diseased wood, which looks burned or black.
Prune 1 foot beyond the affected tissue and sanitize the pruners between each cut with rubbing alcohol or a diluted 10% bleach solution. Avoid excessive nitrogen fertilization, and only prune apple trees when they’re dormant to help prevent new growth from being infected.
Copper fungicide is the only chemical treatment available to homeowners to control fire blight. As with any pesticide, read all instructions on the label and wear proper personal protective equipment. To control fire blight, the copper fungicide must contact the open blossoms where the infection begins which may put pollinators at risk.
“Try to apply on a dry day with low wind when pollinators are less active,” Little said.
Keep squirrels and birds away from growing fruit by wrapping the tree canopy in a light bird netting once the tree has set fruit and secure it around the trunk with a flexible plant tie.