It Takes Two to Tango

By Dr. Francis Gouin

At a recent garden club lecture, a member complained that she was not seeing apples on any of the five trees she planted three years ago. The trees were growing in full sun and had a full compliment of blooms this past spring. All were of the Golden Delicious variety.
    Were any flowering crab apple trees in her area, I asked.
    She was not aware of any.
    That’s why her trees have no fruit.
    When selecting apple and pear trees, nut trees such as pecans and walnuts and shrubs such as blueberries, filberts and elderberries, you’re probably dealing with clones, and they can have pollination problems.

    Nearly all of the fruit and nuts that we consume are grown on plants that have been vegetatively propagated. Plants vegetatively propagated from root cuttings, rooted cuttings, grafting or tissue culture are genetically identical. Many genetically identical plants cannot pollinate. So you must plant two or more different varieties in close proximity.
    This gardener should have planted Red Delicious, Gala, Honey Crisp or even a flowering crab apple in the same planting. By planting two or more different varieties, she would have assured cross-pollination, and there would be fruit. Of course for cross-pollination to occur, the plants must flower at the same time.
    The same problem occurs with high bush blueberries.
    If you’re planting blueberries, plant at least three different varieties. Diversity assures good cross-pollination and lengthens your harvesting season. Blueberries tend to flower at the same time, but varieties have different periods of maturation.
    Last year, a gardener complained that her patty-pan squash produced hardly any fruit though the plants were vigorous and healthy. I suggested that she plant yellow summer squash and/or zucchini squash in close proximity to serve as a pollinator.
    In many species, fertility depends on cross-pollination, which in turn depends on bees to transfer the pollen from one flower to another.