Pollination of Fruit

A variety of plants in Texas experience fruit problems every year, from bearing no fruit at all to instances where immature fruit drop. However, fruit injury can also occur from frost or subsequent cold temperatures.

However, the weather can't be blamed for all fruit problems. All fruit plants require flower pollination in order to produce fruit. Pollination is the transfer of pollen from the male part of the flower (anther) to the female part (pistil) of the same flower or another flower of the same type. Seeds needed for propagation are derived from the fruit.

Gardeners, however, are more likely to be interested in the particular fruit as a food item, rather than as part of Mother Nature's scheme.

Not all plants will set the maximum fruit crop when pollen is available only from the same plant. Before the maximum amount of fruit will form, pollen must come from different plants of the same kind for cross-pollination. The absence of the second pollinator is often why single trees in the garden flower heavily but never set a single fruit.

Weather does have a bearing on flowering and fruit development, even with several pollen sources available. Windy or rainy weather during flowering often slows bee activity. High temperatures may also dry the female reproductive parts, which prevents pollen grain germination.

Flowers with higher nectar content will often lure bees away from fruit plants that have lower nectar contents in their flowers. Overuse of insecticides during the flowering period will reduce the number of bees and the subsequent pollination of flowers.

In cross-pollination, the pollen of the selected varieties must be compatible. The flowering date of the pollen source must match the flowering date of the plant to be pollinated. If both varieties aren't flowering at the same time, fewer fruit will develop. Some varieties take longer to come to flowering age, but this is only a short-term concern that will correct itself in a few seasons.

Cross-pollination is essential for a maximum apple crop. Trees should be less than 100 feet apart to assure optimum pollen transfer.

Pecans and black walnut trees are self-fertile, but their pollen is often not shed when the stigma of the pistil is receptive, so fruit may begin to form and then drop during the season. Pecans are monoecious, meaning they produce separate male and female flowers on the same tree. Some varieties develop the male flowers—called catkins—first, and are termed protandrous. Other varieties produce the female nutlets first and are termed protogynous. Each type will cross-pollinate with the other. If you are planting two pecan trees, plant one of each pollination type. Varieties that are of the protandrous type (shed pollen fruit) include Cheyenne and Desirable. Varieties that are protogynous (forms bloom first) include Choctaw, Kiowa, Mohawk and Shawnee.

Fruit drop can be a problem with Japanese persimmons due in part to pollination considerations and environmental stress. Separate male, female and/or perfect (both male and female) flowers can be produced on the same tree on the current season's growth. Tane-nashi, Hachiya and Tamopan produce flowers that develop into excellent parthenocarpic (non-fertilized) fruit without pollination and without seeds. These varieties can, however, be pollinated by common persimmon or the Fuyu variety to produce fruit with seeds.

Fruit drop is common on parthenocarpic fruit without true seeds. (Seeds produce chemical hormones that improve fruit retention.) Any environmental stress such as drought, waterlogged soils, extreme-heat, etc. can worsen this fruit drop problem. Thus, a thick layer of mulch over the root zone and regular, deep watering is recommended.

Fruit trees such as nectarine, peach and quince should be able to produce adequate fruit crops alone. Additional trees will increase the harvest and add that extra assurance of enough pollen for all of the flowers. Pear trees are self-fruitful, but a second variety will also improve the crop.

Nearly all of the small fruits, berries and brambles are self?fruitful. Remember, all plants flower and bear fruit as long as the laws of nature are understood and met. When purchasing trees for spring planting, keep these principles of fruit and nut pollination in mind—it could avoid disappointment later.