Fruit Tree Pollination
Pollination is essential for good fruit crops. Different fruit trees have different requirements for pollination so here is our guide to ensuring maximum yields!
For fruit trees to produce fruit, their flowers need pollinating, which is done by flying insects such as honeybees, bumblebees, flies, beetles, and wasps. Many fruit trees have self-incompatible flowers, meaning that they need cross-pollination by another cultivar of the same fruit that flowers at the same time growing nearby to pollinate their flowers. Some fruit trees are self-fertile which means that they bear flowers that can pollinate themselves. However, even self-fertile selections tend to produce a larger crop when another cultivar is planted nearby for pollination.
The Basics
Distance: If you live in a more densely populated area, there may be adequate pollination nearby and you may be fine with having one tree in your garden. Pollinating bees can travel 3 to 4 kms but unless a tree is within 100 feet it will not be reliably effective for cross-pollination.
Flowering time: For cross-pollination to occur, it is critical to plant trees that will flower at the same time. Fruit trees are generally classified into flowering groups so that choosing a cultivar with overlapping flowering times is easy.
Weather: Bees and flying insects need to be active when fruit trees are flowering to pollinate them. Unfavourable weather conditions during flowering (cold and rain) will reduce bee activity so encouraging wild pollinator activity or establishing mason bee populations is beneficial for ensuring tree pollination. Apricot, nectarine, and peach trees flower early in the season and are especially susceptible to weather negatively affecting pollinator activity. Cherry and plum trees also flower earlier in the season and are susceptible to lack of pollinator activity.
Apple Tree Pollination
Timing
For maximum cross-pollination plant apple trees according to when they bloom. Apple varieties in a bloom period can be pollinator partners with other varieties within the same period. Cross-pollination cannot occur if trees do not bloom at the same time.
The average blooming period for apples when pollination can take place is about 9 days. Cool weather during bloom will extend this period, whereas warmer weather will shorten it. Flowering crabapples are the same species as apple trees so they can be used as a pollinator partner, which is useful as they have longer bloom times than apples and are easily cared for.
Triploids
Some apple varieties are unique because they are unable to pollinate other apple trees, their pollen is sterile. They are triploids, containing an extra set of chromosomes, so they cannot be relied upon to give out pollen. For these trees a third apple must be present so that all trees can be pollinated.
Triploid apples:
Bramley’s seedling
Belle de Boskoop
Gravenstein
Jonagold
King
Mutsu
Pear Tree Pollination
As is the case with apple trees, the key to successful pollination is to choose pears that bloom at the same time. Pear blossoms have a short season and small amounts of nectar so twice as many bees are needed for pollination. Asian Pears and European pears will cross pollinate if they are blooming at the same time.
| European Pear Fruiting Variety | Compatible Pollinizer |
|---|---|
| Anjou | Bartlett*, Bosc, Comice*, Conference, Anjou*, Seckel |
| Bartlett* | Anjou, Bosc, Comice*, Conference |
| Bosc | Anjou, Bartlett*, Comice*, Conference, Seckel |
| Comice* | Anjou, Bartlett*, Bosc, Seckel |
| Seckel | Bosc, Comice*, Bartlett* |
*Although Anjou and Bartlett are partially self-fertile, they should be cross-pollinated to produce heavy and regular crops. Bartlett and Comice may set large crops of parthenocarpic (meaning the development of the edible fruit without fertilization; parthenocarpic fruits are seedless) fruit.
| Asian Pear Fruiting Variety | Compatible Pollinizer |
|---|---|
| Chojuro | Shinseike, Bartlett |
| Nijisseiki (20th Century) | Chojuro, Shinseike, Bartlett |
| Hosui | Partially self-fertile; Any Asian pear with the same bloom time or early blooming European pear |
| Kosui | Any Asian pear with the same bloom time or early blooming European pear |
| Shinseike | Chojuro |
Cherry Tree Pollination
Cherry trees require cross pollination from another variety of cherry tree that bloom at the same time. The average bloom period is about 7-8 days; cool weather will extend bloom and warm weather shorten it. Cherries that do not receive adequate pollination will fail to develop. Bee activity is crucial to move pollen within and between flowers.
Varieties which require pollinizers are: Bing, Early Burlat, Lambert, Rainer, and Royal Ann
Varieties which are self-fertile: Glacier, Lapins, Stella, and Sweetheart
Varieties which cannot be relied upon as pollenizers for themselves (cross-unfruitful): Bing, Lambert, Royal Ann
Varieties which are known as universal pollen sources are: Glacier, Lapins, Skeena, Stella, and Sweetheart. Their use as universal pollinizers should also take blooming time into consideration. Early blooming varieties are Lapins and Skeena.
| Cherry Fruiting Variety | Compatible Pollinizers |
|---|---|
| Bing | Compact Stella, Early Burlat, Montmorency*, Rainier, Sam, Stella, Van |
| Early Burlat | Bing, Lapins, Sweetheart |
| Lambert | Compact Stella, Montmorency*, Rainier, Sam, Stella, Van |
| Montmorency (*tart cherry) | Self-fertile |
| Rainier | Bing, Compact Stella, Lambert, Montmorency, Royal Ann, Sam, Stella, Van |
| Royal Ann | Compact Stella, Montmorency*, Rainier, Sam, Stella, Van |
| Stella, Compact Stella, Sweetheart, Glacier | Self-fertile |
| Van | Bing, Compact Stella, Lambert, Montmorency, Rainier, Royal Ann, Sam, Stella |
Plum Tree Pollination
There are two major groups of plum trees: European and Japanese. European and Japanese plums cannot cross-pollinate each other. European plums are partially self-fertile but will bear more heavily with a second tree that flowers at the same time. The Japanese hybrids require a second Japanese variety that flowers at the same time for cross pollination. For more details see below.
European plums that are self-fertile: Blue Damson, Green Gage, Italian Prune, Stanley, Yellow Egg
European plums that require pollinizers: Seneca
Japanese plums that are self-fertile: Santa Rosa
Japanese plums that require pollinizers: Satsuma, Shiro
Apricot, Peach and Nectarine Pollination
Apricots are self-fertile but will produce more reliably when another variety is available.
Nectarines and Peaches are also self-fertile trees.
Other Fruit Trees
Cornelian cherry (Cornus mas) - Two different varieties required
Fig - Self-fertile
Lemon - Self-fertile
Olive - Self-fertile but better production when planted with another variety
Medlar - Self-fertile but better production when planted with another variety
Mulberry - Self-fertile
Paw-paw - Two different varieties required
Persimmon - Two different varieties recommended
Quince - Mostly self-fertile, but planting with another variety can improve fruit set
Pollination Troubleshooting:
Fruit that does not receive adequate pollination can become malformed as they develop, or will result in early fruit drop.
If your tree produces flowers but no fruit, it is a pollination issue. Unusually cold temperatures during flowering can damage buds resulting in fewer or no fruit.
If your tree produces few flowers than pollination is not an issue. Too much shade or improper pruning can cause decreased flowering.
Fertilization with high nitrogen fertilizer encourages leaf and shoot growth and is best for young trees prior to fruiting age. Once trees are of fruit bearing age, fertilizer higher in phosphate encourages flower and fruiting.
If there was a heavy crop load in the previous year the tree may be depleted somewhat resulting in less fruit the following year until the tree “recharges”.
Small Space Pollination Tip:
In a small garden there may not be room for multiple fruit trees. Combination fruit trees have different varieties grafted onto a single tree and these varieties pollinate each other so you only need one tree.
The Basic Science
What even is a fruit? A fruit is an edible reproductive body of a plant. The evolutionary function of a fruit is to spread the seeds or to attract “dispersers”.
For a fruit to form, a flower needs to be pollinated, which requires pollen. The male anther produces pollen and is transferred to the female stigma. When this happens, the growth of the pollen tube is activated, the ovules are fertilized by the sperm, and the ovary begins to transform into the fruit. It is the ovary and the surrounding tissue that eventually becomes the fruit we eat.
Many blossoms have both male and female flower parts (making them hermaphroditic) but for fruit trees that are not self-fertile, or require cross-pollination, the pollen of one cultivar needs to come into contact with the stigma on another cultivar (of the same species).
