Answer: There are a handful of reasons your apple trees are not flowering:
Plant Immaturity -- All plants must be physiologically mature before they are capable of blooming. During the juvenile stage of growth, plants do not bloom. For annuals, such as marigolds and petunias, the juvenile stage may last for only a few weeks. Trees, however, may not be physiologically mature for 10 or more years. Apple and pear trees planted in the backyard garden may not flower and bear fruit for 4 to 6 years. The actual length of time from planting to flowering varies tremendously. Differences exist among varieties or cultivars. Generally, a Jonathan apple tree will bear fruit sooner than a Red Delicious. Dwarf and semi-dwarf fruit trees bear earlier than standard-sized trees. Lilacs may not bloom for 3 to 5 years after planting.
Winter Injury -- The flower buds of most plants are generally less hardy than the leaf buds. Low winter temperatures may kill the flower buds without damaging the leaf buds. For example, temperatures below -20?F will kill the flower buds on some apple trees.
Alternate Flowering -- Some trees, such as fruit trees and crabapples, bloom heavily one year and then sparsely the following year. Hand thinning of excess fruit on fruit trees will help to overcome this tendency to flower and bear fruit in alternate years. 'Bob White,' 'Dolgo,' and 'Red Splendor' are three crabapple varieties that tend to flower heavily in alternate years.
Cultural Practices -- Heavy pruning and excessive nitrogen fertilization promote vegetative growth and inhibit the production of flower buds. Generally, fertilization of trees and shrubs is unnecessary if the plant is growing well and possesses good leaf color.
Insufficient Sunlight -- Many trees and shrubs require at least 6 to 8 hours of direct sunlight in order to bloom properly. Generally, the amount of flowering decreases as the shade increases. Your apple trees need full sunshine to thrive.
Hope this sheds some light on the possibilities.
Q&A Library Searching Tips