Most fruit trees require cross-pollination to yield a crop of fruit.
The process involves the pollen of one plant being transferred to another, yet compatible, species of the same plant. This can also be achieved by grafting two or more varieties on one truck. Pears, sweet cherries, and Japanese plums fall into this category. Other fruit trees, such as peaches, figs, and sour cherries, are self-fruitful meaning they yield fruit from their own pollen. Another group of fruit trees, including most apples, are semi-self-fruitful. Trees in this group will produce an adequate crop without cross-pollination, but yields increase with cross-pollination.
The cross-pollination varieties must bloom at the same time and be compatible with one another. The length of the blooming season varies from 7 to 15 days depending on the fruit, varietal strain, and weather. Cold, windy, and wet weather can prevent bee activity and, therefore, hinder cross-pollination during fruit blooming.
APPLES & PEARS
In order for apple and pear trees to produce fruit, there has to be a second tree for cross-pollination to occur. As long as a second tree is within 500 feet of the first, pollination should take place. If your apple or pear trees are not performing to satisfaction, the following list will help you trouble-shoot:
Cool, rainy weather conditions during flowering – Unfortunately, other than hoping for better luck next year, there is nothing that can be done.
Old, unproductive trees that don’t flower – Generally, apple and pear trees have a productive lifespan of about 30-40 years. Trees can be rejuvenated by removing old, unproductive growth and allowing new growth to replace it.
A poor crop the year after a bumper crop – Some apple varieties tend to perform biennially, with a great crop one year, not so great the next and a better crop again the third year.
No trees of the same genus nearby – It is always best to pollinate fruit trees of the same genus with each other (apples with apples, pears with pears) but pears can cross-pollinate with apples as long as both trees bloom at the same time.
The other cultivar in the yard is sterile – Some (but not all) crabapple trees work for cross-pollination. A few varieties have sterile pollen.
Lack of pollinating insects – Try adding to your flowerbeds. Most flowering plants are guaranteed to attract bees. The annual herb Borage and the perennial Bee-Balm (Monarda) are especially good for this purpose. Due to their flowering times coinciding with those of many fruit trees, marigolds, pansies, spurge, trollius and arabis are the best choices.
The trees are of the same variety – Clones will not pollinate each other. For example, a Norland apple tree cannot pollinate another Norland apple tree.
APRICOTS
European apricots are self-pollinating. Manchurian and Siberian apricots fruit more dependably with other apricot varieties or Nanking cherries.
CHERRIES & PLUMS
Sour cherries are self-pollinating. In order for cross-pollination of the remainder of cherries and plums to occur, it is essential that they bloom at the same time. Many chokecherries will also aid in cross-pollination. Plums must be from the same region of the world to cross-pollinate (European plums with European plums, Asian with Asian, etc.). The closer the relationship between species, the more abundant the fruit will be.
GRAPES
Grapes are self-pollinating. Cross-pollination is not essential, but some hybrids may have non-viable pollen. Planting two or more varieties will solve the problem.
BLUEBERRIES
Blueberries are self-pollinating but two or more varieties result in better yields and larger berries.
CURRANTS & GOOSEBERRIES
Currants and gooseberries are self-pollinating. Excellent fruit production can be obtained with just one plant. If currants are grown near gooseberries or jostaberries, however, yields can be even better.
STRAWBERRIES & RASPBERRIES
Strawberries and raspberries are both self-pollinating.
KIWI FRUIT
Both male and female plants are required to produce fruit. You need at least one of each plant but a male can cross-pollinate up to 8 females. Plants must be 2-3 years old before they can produce fruit.
