Pollination is the transfer of pollen from the male part (anther) of a flower to the female part (pistil) of the same flower or another flower of the same sort. A pollinizer is a plant that provides the pollen to the flowers of a different plant variety. In most instances, bees are the agents that transfer the pollen, thus referred to as the pollinators. Little or no pollination occurs as the result of wind movement. To be an effective pollinizer, a variety must
- have a bloom period that overlaps that of the variety to be pollinated,
- have a diploid chromosome makeup,
- produce viable pollen, and
- be grown in close proximity to the variety to be pollinated.
Several environmental factors affect pollination. Temperatures below 55 to 60°F reduce bee flight and activity, as do windy conditions. Temperatures above 85 to 90°F dry the flower's stigmatic surface and prevent pollen grains from germinating. Because bees naturally seek out the best nectar-producing flowers, other blooming flowers in the area can attract bees away from fruit plants, which generally are poor nectar producers. In the early spring, dandelions in bloom can attract bees away from the flowers of fruit plants. Finally, applying insecticides during bloom can harm bees or other pollinating insects.
The best time to plan for pollination is when you order your plants. Most nurseries have charts or tables recommending varieties that will serve as pollinizers for each other. You should also be aware of your neighbors and what fruit plants they have. To be effective, a pollinizer does not have to be directly next to your plant. Also remember that some ornamental plants, such as crab apples, flowering pears, and plums, can be effective pollen sources if their bloom overlaps that of the planted fruit.