Thousands of apple varieties have been grown since ancient times. Many are lost to posterity, but more varieties of apple still exist today than of any other fruit. Breeding for disease resistance has focused on the apple more than any other fruit. After the June drop and when the fruit is no more than 1 inch in diameter, thin to 8 inches apart, or remove about 10% of the total fruit. Also thin all clusters to just one fruit. The inclination of the apple branch is thought to determine its fruitfulness: the more horizontal, the more fruit. U.S. researchers have shown that shining red lights on apple trees for 15 minutes each night beginning 2 weeks before harvest, delays fruit drop for 2 weeks.
For summer apples, pick fruit just before fully ripe, otherwise the apples become mealy. In the fall, pick fruit only when fully ripe. Make sure you pick with the stems, or a break in the skin will occur that will permit bacteria to enter and foster rot. Be aware that ripening apples give off small amounts of ethylene gas that may inhibit the growth of neighboring plants and cause early maturing of neighboring flowers and fruits.
Wrapping in oil paper or shredded paper helps prevent scald. Some apples stored over the winter develop a rich flavor that is excellent for pies. Some summer apples keep better if held at high temperatures several days before storage. Do not store apples with potatoes because apples will lose their flavor and potatoes will develop an off flavor. Fresh apples can be stored in cool place (32°-40°F) at 80%-90% humidity level for 4-8 months.
Height - Dwarf: 6-12 ft. Semidwarf: 12-18 ft. Standard: 20-40 ft.
Spacing - Dwarf: 8-20 ft. Semidwarf: 15-18 ft. Standard: 30-40 ft.
Root Depth - 10 ft. or more, with a spread 50% beyond drip line
pH - 6.5-7.0
Bearing Age - dwarf and semidwarf 2-3 years; standard 4-8
Pollination - Most need cross-pollination.
Chilling Requirements - 900-1000, though some require less hours below 45°F
Site - South-east exposure; clay loam. To espalier, some experts suggest siting apples on an eastern wall or slope in very hot summer climates to avoid sunburn.
Water - Medium
Fertilizer - Low N for young trees under 2 years. Appropriate new growth is 6-14 in.
Side-dressing - Apply compost late autumn and work into soil.
Support Structures - Branches may need support when fruiting; branch separators can increase yields.
Training - Free-standing: central leader; wire-trained: all cordons, espalier, fans, stepovers, palmettes.
Pruning - Spur-types require little annual pruning since spurs bear for about 8 years, but each spring remove 1 out of 10 spurs and thin fruit by 10%. Tip-bearers fruit on 1-year-old wood. For these, prune back some of the long shoots and some of the spurs. For bitter pit, a sign of unbalanced growth, remove the most vigorous shoots at the end of the summer.
Pests & Diseases
Aphid, apple maggot, cankerworm, codling moth, European apple sawfly, European red mite, flea bittle, fruit worm, gypsy moth, leafhopper, leafroller, mite, oriental fruit moth, pearslug, plum curculio, potato leafhopper, scale, tent caterpillar, weevil, whitefly, white grub, wooly apple aphid.
Apple scab, baldwin spot, canker dieback, cedar apple rust, crown gall, crown rot, cytospora canker, fire blight, powdery mildew, sunscald.