Growing Fruit Trees in Maine - Pollination Requirements
In order for fruit to develop, flowers must first be pollinated. Some species of fruit trees require cross pollination by another variety, whereas others will bear fruit when planted alone or with the same variety. When flowers have not been properly pollinated, they are shed soon after bloom.
Fruit trees belong to one of three groups depending on whether or not they need another variety planted in the same orchard. These are the self-fruitful, partially self-fruitful, and self-sterile groups. Self-fruitful trees will accept pollen from flowers of the same variety and will produce fruit when planted alone. A fruit tree that is partially self-fruitful will have a light crop of fruit when planted alone, but will have more fruit when planted with another variety. The self-sterile tree fruits need cross pollination by another variety and will only produce fruit when another variety is planted nearby.
Apples are self-sterile. A McIntosh apple tree will not bear fruit when planted with only McIntosh trees. In this case, it is best to have at least two trees, each a different variety of apple, such as Honeycrisp and Northern Spy. Apples will be cross pollinated by crab apples and vice versa. For optimum cross pollination, plant two varieties close to each other and which bloom at roughly the same time. Some apple varieties have sterile pollen and cannot be used for cross pollination. These are Baldwin, Creston, Gravenstein, Jonagold, Boskoop, Mutsu, Crispin, Rhode Island Greening, Roxbury Russet, Shizuka, Spigold, Stayman, Bramley’s Seedling, Wealthy and Winesap. When growing any of these varieties, plant at least two other varieties for good cross pollination.
European and Asian pears are partially self-fruitful, so they will bear a small number of fruit without cross pollination. The Seckel and Bartlett varieties of pear will not cross pollinate each other. Asian and European pears do not reliably cross pollinate each other.
Asian and hybrid plums are self-sterile, but European plums are partially self-fruitful. Planting two or more varieties will ensure that trees bear a sufficient number of fruit. Asian plums will not be cross pollinated by hybrid or European plums since they bloom at different times. In addition, plums have complex pollination requirements. Some varieties will not pollinate other varieties, a condition known as incompatibility. The easiest solution to this problem is to select a variety that is known to be a good source of pollen for most other varieties. Toka, South Dakota and Superior are hybrid plum varieties that will successfully pollinate most other hybrid plum varieties. Early Golden will pollinate many varieties of Asian plum.
Some sweet cherry varieties are self-fruitful and others are self-sterile. Sweet cherry varieties that cross pollinate most other varieties are Black Gold, Hedelfingen, Kristin, Lapins, Seneca, Stella, Regina, Valera and White Gold. Tart cherries will not pollinate sweet cherries, and vice versa.
Peach and most tart cherries are self-fruitful. They will bear fruit when one tree or one variety is planted by itself. Some tart cherries may be partially self-fruitful.