Pollination Requirements for Various Fruits and Nuts

Fruit plants generally require pollination in order to produce fruit. Two major exceptions are known. They are apomixes, which occur in citrus, and parthenocarpy, which can occur in Bartlett pears in California under certain conditions and in bananas.

The plant that supplies the pollen is called the pollinizer. The agent, usually a honeybee or other insect that does the transferring, is called a pollinator.

To be an effective pollinizer, a variety must:

• Have a bloom period that overlaps that of the variety to be pollinated
• Have a diploid chromosome make-up
• Produce viable pollen
• Be grown in close proximity to the variety to be pollinated

Several climatic factors affect pollination.

• Temperatures below 55–60°F reduce bee activity.
• Temperatures above 85–90°F dry stigmatic surface and pollen grain doesn't germinate.
• Windy weather slows bee activity.
• Rain during anthesis (time stigmatic surface is receptive)
• Presence of other flowers—the fruit plants generally are poor nectar producers and bees will naturally seek out the best nectar-producing flowers
• Most insecticides will reduce bee activity; therefore, do not spray them during bloom.

Pollination Requirements for Several Crops

Those fruits listed as self-fertile will set fruit with their own pollen.

• Apple: Cross-pollination is always needed to produce adequate fruit crop.
• Apricot: All varieties are self-fruitful but cross-pollination is helpful.
• Blackberry and Dewberry: Most are self-fruitful but a few are not, and a crop requires cross-pollination.
• Blueberry: Fruit set and crop size are improved by cross-pollination.
• Cherry:
  • Sweet: Most varieties are self-unfruitful. However, there are newer varieties that are self-fruitful, such as Lappins, Stella, Whitegold, Sweetheart, and Blackgold.
  • Red tart: The commercial varieties are self-fruitful.
• Currants: Self-fruitful
• Gooseberry: Most varieties are self-fruitful.
• Grape: Most are self-fruitful.
• Nectarine: Most varieties are self-fruitful; however, those having J. H. Hale in the parentage will require cross-pollination.
• Peach: All commercial varieties, except J. H. Hale, are self-fruitful.
• Pear: A few varieties are self-fruitful, but a pollinizer will improve the crop.
• Plum: A wide diversity occurs in the plums. About half of the varieties are self-fruitful and half are not. To be on the safe side, pollinizers should be provided.
• Quince: All varieties are self-fruitful.
• Raspberry:
  • Black - mostly self-fruitful
  • Purple - self-fruitful
  • Red - mostly self-fruitful, but crop size is improved by cross-pollination.
• Strawberry: Varieties are known that produce imperfect flowers, but most varieties planted are self-fertile.
• Persimmon:
  • American - Self-fruitful
  • Japanese - Three types of flowers are produced on the same tree. It is a good idea to plant at least two trees to ensure good fruit production.
• Almond: Must be cross-pollinated by another variety.
• Beech: Self-fruitful
• Black Walnut: Self-fertile, but often the pollen is not shed when stigma is receptive. Use at least two varieties or seedlings to ensure good crops.
• Huartnuts: Hybrids of butternut and heartnut, believed to be self-fruitful
• Butterjap: A butternut x sieboldii hybrid. Self-fruitful.
• Carpathian Walnut: Self-unfruitful; at least one other seedling tree required to ensure a crop.
• Chestnut, Chinese: All are self-sterile. Two or more varieties or seedling trees are necessary to ensure adequate cross-pollination.
• English Walnut: See Carpathian Walnut.
• Filbert: Best to plant at least two varieties or seedlings to ensure pollination.
• Hazel: Same situation as Filbert.
• Heartnut: Best to plant two varieties or seedlings to ensure pollination.
• Hican: Many types of hickory x pecan hybrid. Usually considered self-fruitful.
• Hickory: Best to plant at least two seedlings to ensure pollination.
• Japanese Walnut: See Heartnut
• Pecan: Self-fertile. Wind pollinated
• Persian Walnut: See Carpathian Walnut
• Pistachio: Must be cross-pollinated.
• Siebold Walnut: See Heartnut