Fruit tree pollination is complicated
Part two of a series on fruit trees
 

[February 25, 2021]   Whether you have a single fruit tree or a small grove in the backyard, having the correct pollination is key for fruit production. However, for some species that is easier than others.

For example, let’s look at apples. Apples are probably the most misunderstood group of our fruit trees when it comes to their pollination requirements. We have all heard that you need two apple trees to produce fruit. While that is true, the details are often left out. It’s not enough just to have those two apple trees. There are other considerations. They will need to bloom at the same time, and there will need to be insects around for pollination.

Here are two other ways fruit tree pollination can be complicated:
 

Pollination varies among fruit trees

There are a lot of terms to describe the kind of pollination that goes on in the home orchard. The first group – and the easiest – are those considered “self-fruitful.” Self-fruitful trees do not need to be cross-pollinated by another tree. Peaches and tart (sour) cherries are the best example for our area.

The second group are those fruit trees considered to be “partially self-fruitful.” Without the presence of another variety, partially self-fruitful trees will set a crop of fruit on their own, but would much rather be cross-pollinated, proving even more fruits. European plums and apricots (very questionable in our area) and a couple of apples, Rome and Golden Delicious, fall into this category.

The third group are “self-unfruitful.” This means without cross-pollination there will be no fruit. This is where most of our apples fit in, along with pears, Japanese type plums, and sweet cherries (although Stella is self-fruitful). This also is where that expression about apples needing two trees can go bad. You do need two trees, but two different varieties that bloom at the same time! The same holds true for pears and sweet cherries (Stella could be one of those). We do have kind of a “get out of jail free” card with apples, at least in many suburban or urban areas. Our flowering ornamental crabapples – when in bloom at the same time – can serve as the pollinator tree for our fruiting apples.

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Apples have yet another “group” when planning the home orchard. There are some considered “pollen sterile.” These apple varieties can receive pollen from other trees and produce a crop yet are unable to contribute pollen themselves. This is again where the “only two trees needed” falls apart. If a pollen sterile variety is used, there needs to be a third apple variety to ensure there is fertile pollen available.

Winter hardiness plays a role

For fruit trees another question to ask is not so much, “Will the trees survive the winter?” but more “Will the flower buds survive the sheer cold?” Fruit trees will lose a percentage of flower buds once temperatures get to a certain temperature, and if those temperatures continue, 100 percent loss will happen. The most susceptible fruit buds are apricot and sweet cherry. The very susceptible include peaches and nectarines, which makes them questionable for having a crop every year in our area. Moderately susceptible are our plums, pears, and tart (sour) cherries. The apple comes in as the least susceptible to cold winter weather, but it still may be impacted.

I will continue this topic of fruit trees soon, and you may want to check out the first in this series: “Fruit trees have a place, even in a small yard.” You also may want to check out these upcoming virtual events: the 2021 Fruit & Vegetable Virtual Conference and the Stateline Fruit and Vegetable Growers Conference.

[Posted by Richard Hentschel, University of Illinois Extension, Horticulture Educator]