Gardeners rarely give thought to pollination in their vegetable gardens, planting rows of vegetable crops and letting bees and butterflies take care of the rest. Because fruit trees take up more space and are a larger investment of time and money, gardeners rarely have space or inclination to plant large numbers of trees, like commercial orchards do. Nonetheless, if you want your trees to produce fruit, understanding and meeting pollination needs is essential.
Your fruit trees require pollination to produce fruit. Flowers and fruit are reproductive structures of plants. The male parts of flowers, called stamens, produce pollen that carries sperm cells to the female part of the flower, called the pistil. At the base of the pistil lies the flower's ovary, and when fertilization occurs, the flower produces seeds and encloses them in a layer called the pericarp, the fleshy outer coating consumed as fruit. Without pollination, fertilization and fruiting do not occur.
There are two types of pollination that you'll hear about in reference to fruit trees: cross-pollination and self-pollination. Cross-pollinated trees require and will only produce fruit after pollination from another variety or species of tree. Self-pollinated trees can be pollinated by other trees of the same species or even the same tree.
According to the Colorado State University Extension, fruit trees are rarely pollinated by the wind. Instead, they rely on insects to carry pollen from tree to tree, especially the honeybee. The University of Missouri Extension states that most fruit trees planted in the home garden have adequate wild bees for pollination--a single honeybee can pollinate 5,000 flowers in a single day.
When purchasing fruit trees for your home, consider the tree's pollination needs before bringing home a tree. Many trees require another variety nearby; for example, most apple trees can be cross-pollinated with a crab apple tree. Even trees that will self-pollinate will often produce more and heavier fruit if they are cross-pollinated. Some trees are grafted with multiple varieties on a single tree to meet pollination needs. If you have an existing tree but no cross-pollinator, the Colorado State University Extension recommends hanging buckets of water from the branches and filling them with bouquets of flowering branches from a cross-pollinating variety.
Michele R. Warmund of the University of Minnesota Extension reminds gardeners that not all varieties of trees will successfully cross-pollinate with another. Some--such as the triploid Mutsu and Jonagold apple varieties--are bred sterile, while others have blossoms open at incompatible times. When planning your home orchard, check that the varieties you've selected to plant are compatible and will cross-pollinate each other.