The A Bees Cs of Pollinations

By Dr. Francis Gouin

A Bay Weekly reader complains that her apple trees have not produced any fruit during the five years that she has had them in her garden. All five, she told me, are of the same variety: golden delicious trees. She was told that for the trees to produce fruit, she needed to plant more than one tree. Since her preference was for Golden Delicious, that is what she purchased and planted.

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    She was traveling to an orchard under bad advice. Golden Delicious is a clone, and clones cannot pollinate themselves. Apples require cross-pollination from a different variety to produce fruit. The pollen from the Golden Delicious apple flower cannot pollinate the stigma of that same flower or an adjoining flower.
    For an apple to be produced by the Golden Delicious apple tree, the pollen has to come from a different variety. She should have planted a Red Delicious, Jonathan, Gala, Granny Smith or such as a pollinator.
    This is where bees come in. In their search for nectar, bees carry pollen on their hind legs. As they enter the flower, the pollen from their hind legs brushes against the stigma of the flower, resulting in cross-pollination. You can do the same thing with a small camel’s hair brush as plant breeders do when their intent is to develop a new variety.
    Even though the pollen is from another variety, the fruit remains Golden Delicious because the flesh of the fruit is maternal, derived from the ovary wall.
    For this reason, all fruit trees are propagated by grafting, budding, tissue culture or cuttings. If you were to plant the seeds from a Golden Delicious apple, you can rest assured that the resulting seedling would not be Golden Delicious. The seedling would be a genetic combination of all the sources of pollen that have contributed to it. We call those Heinz 57 flavors.
    Cross-pollination is essential for nearly all of the fruit we eat. This is why bees are so important in the production of horticultural crops. Butterflies, hummingbirds, flies and many more insects also contribute to the process.

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