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.

Fruit Trees

Apples -- Apples are considered self-unfruitful. Most apple varieties will set a small crop with their own pollen. For maximum production, however, plant at least two different varieties with overlapping bloom periods to insure cross-pollination and fruit set. Apple cultivars can be classified as early, mid, and late season blooming. The bloom periods of early and mid-season bloomers overlap, permitting adequate cross-pollination and fruit set. Good pollination can also be expected with mid and late blooming varieties. However, the bloom periods of early and late blooming varieties may not overlap, resulting in poor pollination. (Additional information on blooming times can be found in Pm-1052 Tree Fruit Pollination and Pm-453 Fruit Cultivars for Iowa.) Most flowering crabapples will pollinate nearby apple trees if they bloom at the same time.

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 European pears are self-unfruitful. Plant at least 2 different varieties for maximum fruit production.

Plums -- Japanese plums are not reliably hardy in Iowa. However, 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. Plant 2 or more hybrid plum varieties to insure cross-pollination and fruit set. 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.

Small Fruits

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 April 13, 2001 issue, p. 37.