The Pollination Of Fruit Trees

Do you want fruit trees in your garden, or even to create a small orchard? No problem, but a little thought is required before any purchase. Not only does each fruit tree have its own requirements, but it will also need well-chosen companions in order to offer you beautiful fruit in good quantities. Yes, plum trees, apple trees and other hazelnut trees are rarely fertile if they are isolated. And even if they belong to the same species, some of them are incompatible from the start, prohibiting any fruit from their union. Here are some tips on how to know who to marry!

How is a fruit tree pollinated?
Male flowers, female flowers, and mixed flowers!
Fertilization in fruit trees is not so simple, between those that can self-pollinate, those that are compatible, and the others!

Bisexual species
Monoecious fruit trees have both male and female organs on the same individual.
Strict monoecious trees have these organs on different flowers, so male and female flowers. They often have a staggered maturity, this is for example the case of the hazel tree.
And there are the hermaphroditic fruit trees (monoecious hermaphroditism), that is to say that each flower carries both male and female organs.

Some are self-fertilizing, so they can be the only ones of their kind and produce fruit with their own pollen. Many small fruit trees are self-pollinating, such as raspberries and currants, but also peach trees, apricot trees…
Other fruit trees, on the other hand, are only fertilized by cross-pollination, meaning that they need another member of their species nearby to be able to produce fruit. They are said to be “self-sterile”. Most apple and pear trees are self-sterile, as well as some varieties of cherry and black currant.
Monosexual species
These are the so-called “dioecious” species, they have either male or female flowers on one foot. They are species of fruit trees that absolutely require a cross-pollination of fruit trees, they are allogamous. The kiwi is generally a dioecious species.

Cross-pollination
It is important to know that cross-pollination of fruit trees gives better results in all cases, because there is a crossing of genes, and therefore enrichment, while self-fertilization causes a depletion of genes. Cross-pollination will lead to better fruiting, with larger and more abundant fruit, better shelf life and better conservation. The fruit set is also better and the fruit trees sensitive to alternation show a less marked phenomenon.

To know: the fruit set is the phase where the flower turns into a fruit. In terms of biology, it is the ovary of the flower that transforms when it has been fertilized.

Nature favors this type of fertilization by preventing self-fertilization by various stratagems: in monoecious species, there is a time lag between the maturity of female and male flowers, and hermaphrodites see the stigmas and stamens mature at a different time. Self-sterile fruit trees are forced cross-pollinators, due to a hormone, auxin, which will inhibit the germination of pollen from a flower of the same individual.
For a tree of one variety to be pollinated by a tree of another variety, it is essential that the two fruit trees flower at the same time, but this is not the only condition: the two pollens must be compatible since the pollen of one variety is not necessarily capable of fertilizing the ovule of certain other varieties. Moreover, some varieties are better pollinators than others, so the choice of pollinators is crucial for your future production.

Insects and pollination

Our fruit trees are entomophilous species, which means that insects are responsible for most of the pollen transport. The wind participates slightly in this transport, but the production that it allows is very low compared to that offered by the insects.
There are many species of insects that do this great work, but the main ones are bees, which alone account for 60 to 90% of pollinators, and bumblebees. Other insects that pollinate fruit trees include beetles, wasps, flies, butterflies and thrips.
And these pollinating insects need to feed throughout the year, the flowers of fruit trees last a short time, so the diversity of flowering plants must be important, with staggered blooms. Bumblebees are the earliest, coming out to forage even before the end of winter. The overwintering bumblebees will feast on the catkins of willow or hazelnut. The bees arrive only a little later. Dandelions, lesser celandine and other early field flowers are valuable.

To help bees in your garden, read our article on the 20 favorite flowers of bees.
The presence of shelters is also important, whether they are natural or made by the gardener’s hand: hedges and flowery meadows, insect hotels… Installing a hive near your fruit trees is also to be considered, and it requires little care as long as it is not to collect honey.
During the pollination of fruit trees, not all the flowers of the fruit tree need to be visited (and thus pollinated), a fruit tree usually has more flowers than fruits. In general, only 10% of the flowers need to be pollinated to obtain a normal harvest.

How to ensure the pollination of fruit trees?

The almond tree

It blooms during winter, between January and March. Its earliness makes it very interesting for foragers, since it is the first fruit tree to bloom, and its nectar is quite abundant and sweet. On the other hand, this early blooming time is not good for the almond tree because there are few insects at that time (bees for example do not forage below 14°), so you have to rely on the wind as well as bumblebees to transport its pollen.
Depending on the region, choose late varieties and/or take into account the direction of the prevailing winds when planting. Moreover, the flowering is sensitive to frosts.

Place your almond trees close enough together, 5 to 6 meters.

Table of pollinating varieties of almond trees

The blackcurrant tree

The cherry tree

The pollination of cherry trees is complex due to the presence of 3 different species:

The periwinkles and the guignes, called sweet cherries, are Prunus avium, from the cherry tree. They are most often self-sterile and incompatibilities are frequent, it is preferable to associate 2 or 3 pollinating varieties.
Morello cherries are sour cherries from the Morello cherry tree, Prunus cerasus. Most of them are self-fertile but they benefit from being pollinated by sweet cherries.
The true cherries or English cherries are hybrids between these 2 species. Most are also self-sterile.
The cherry tree offers many attractive flowers from March to April, depending on the climate. A minimum of 5°C, up to 14°C, is required for the pollen to be released. The planting distance between two fruit trees for pollination is about 25 meters.

In the orchard, you will place 1 pollinating variety among 8 varieties to be pollinated.

Table of pollinating varieties of cherry trees

Tableau des variétés pollinisatrices des cerisiers