In the flower, pollination is the transfer of pollen from the anther to the stigma. After pollination and fertilization, fruit set occurs. There are two types of pollination. Self-pollination occurs when the pollen is transferred from the anther to the stigma on the same flower, from another flower on the same plant, or from a flower on another plant of the same variety. Self-pollinated plants are said to be self-fruitful. Many plants cannot produce fruit from their own pollen and are considered self-unfruitful. These plants require cross-pollination for fruit set. Cross-pollination is the transfer of pollen from one plant to the flower of a genetically different plant or variety.
Pollination is an important factor when selecting and planting tree and small fruits. A list of pollination requirements for the various fruits is presented below.
Apples -- Most apples are self-unfruitful. A few varieties, such as Jonathan and Golden Delicious, set a good crop without cross- pollination. Generally, however, plant at least two different varieties for maximum production. (Most flowering crabapples will pollinate nearby apple trees.)
Apricots -- Few apricot varieties are reliably hardy in Iowa. Moongold and Sungold are hardy and self-unfruitful. Plant at least one of each for proper pollination.
Cherries, Sour -- Sour or pie cherries are self-fruitful.
Cherries, Sweet -- Sweet cherries are not reliably hardy in Iowa. Most varieties are self-unfruitful.
Peaches -- Peaches are not reliably hardy in much of Iowa. Most peach varieties are self-fruitful.
Pears -- Most pears are self-unfruitful. A few varieties, such as Kieffer, will set a fairly good crop without cross-pollination. However, for maximum fruit production plant at least two different varieties. Plums -- Japanese plums are not reliably hardy in Iowa. However, some European and hybrid plums can be successfully grown in the state. European plums are partially to entirely self-fertile. Hybrid plum varieties (crosses between American and Japanese plums) are self-unfruitful. European plums will not pollinate the hybrid plums and vice versa.
Fruit trees which require two different varieties for pollination should be planted within 50 to 100 feet of one another to insure good fruit set.
Blueberries -- Plant two or three different varieties for maximum production.
Currants -- Currants are self-fruitful.
Gooseberries -- Gooseberries are self-fruitful.
Elderberries -- Elderberries are essentially self-unfruitful. Plant two or more varieties to insure good fruit set.
Grapes -- Grapes are self-fruitful.
Raspberries -- Raspberries are self-fruitful.
Strawberries -- Strawberries are self-fruitful.
Home gardeners should keep these fruiting requirements in mind when browsing in garden centers or leafing through garden catalogs.
This article originally appeared in the March 2, 1994 issue, pp. 1994 issue, pp. 19-20.