Fruit trees can be divided into three categories when it comes to pollination. Self-Sterile, Self-Sterile Triploid, & Self Fertile.
Self-Sterile
These plants produce pollen themselves but require pollen from a different variety to produce fruit. Usually if you plant two compatible self fertile varieties near each other they will be able to pollinate each other, hence each one is a pollinator, sometimes one variety on it’s own will produce fruit but this is where pollen is carried from another compatible variety in the local area. Pollen can be carried for quite a distance by bees gathering nectar for example. Most apples and pears are self-sterile.
Self-Sterile Triploid
These plants produce little or no pollen, so they don’t tend to pollinate other varieties. If planting a Self-sterile Triploid, you need to plant two other pollinator varieties nearby, to produce fruit on all three plants. It’s not that the Self-sterile Triploid needs pollen from two other plants as the name and planting tips may seem to suggest, it’s just that the second pollinating variety (If you only planted one) needs to get pollen from somewhere as well, and the Self-sterile Triploid isn’t going to provide it, so the additional third variety is necessary, hence the second and third varieties pollinate each other and the Self-sterile Triploid gets pollen from one or both of the others.
Self Fertile
Plants which are classed as self fertile have the ability to reproduce when its own flowers stigma receives pollen from its own flowers anther. Most plums are self fertile and some apples but very few pears, pears which are, are usually only partially self fertile. A self fertile fruit tree can produce fruit even when grown on its own. However, in most cases self fertile fruit trees will produce a much better crop when cross pollinated with a different variety.
How to choose compatible pollinators:
For two plants to successfully pollinate each other not only does their pollen have to be compatible but they have to be producing the pollen at the same time, i.e. they have to be in bloom at the same time. Compatible varieties which bloom at the same time are said to be in the same pollination group, Pollination Group 1 is the earliest flowering group, 2 the next etc. Adjacent group flowering times tend to overlap so a plant from 3 may be pollinated by a plant from 2 or 4 (As long as their is an overlap with those particular plants).
Pollination Graphs
Click here for Apple Pollination Graph
Click here for Cherry Pollination Graph
Click here for Pear Pollination Graph
Click here for Plum Pollination Graph.
