Some tree fruit varieties are self-fruitful. A tree of a self-fruitful variety will set fruits when pollinated by pollen from its own flowers or by pollen from another tree of the same variety. In either case such pollination is called self-pollination. Self-fruitful trees may be planted alone or in solid blocks of one variety. Most peach, nectarine, and sour cherry varieties are self-fruitful.
Other fruit tree varieties have various degrees of self-unfruitfulness varying from partially self-unfruitful to completely self-unfruitful. A self-unfruitful tree will not set a normal crop of fruits when pollinated by its own pollen or by pollen of another tree of the same variety. Self-unfruitful trees require pollination by pollen from a tree of a different variety. For example, a ‘Jonathan’ apple tree usually will not set a normal crop of apples unless the flowers are pollinated by pollen from another apple variety such as ‘Lodi,’ ‘Red Delicious,’ or ‘Golden Delicious.’ A tree of a self un- fruitful variety should have a pollinator tree planted within 300 feet.
Cross-unfruitfulness may occur in tree fruits. In some cases, pollen from trees of one variety will not cause fruit set by flowers of another variety. For example, European-type plums will not cross pollinate most Japanese type plums. ‘Winesap’ apple pollen is sterile and will not pollinate ‘Winesap’ or any other variety.
In planning a fruit planting, pollination requirements must be considered if normal crops are to be produced. Pollination requirements are given in the list of suggested varieties for Illinois home orchards.
Honey bees are the most important means of transferring pollen between blossoms. Solitary bees, bumble bees, some types of flies, and other insects also aid in pollen transfer.
Fortunately for the home gardener, sufficient numbers of bees are usually present to accomplish pollen transfer.
Protect bees from injury from insecticides. Do not apply insecticide sprays during bloom. Fungicides can be applied during bloom with little or no adverse effect on bees.