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Pollination

Pollination of fruit trees entails the transfer of pollen from the male part of the flower, the stamens, to the female part, the stigma and then to the ovule where the two parts fuse and fertilisation takes place. This transfer is done naturally,  by bees and other pollinating insects such as hoverflies.

However some trees have particular requirements.

Fruit trees can generally be placed into three categories:

Self fertile trees can pollinate themselves and include some plums, some cherries, very few apples, all quinces. Self fertile varieties also tend to be very good pollinators of other varieties.They will always fruit better if grown with other fruit trees where cross pollination can take place.

Self sterile trees cannot pollinate themselves. Most apples are self sterile, as are all pears, many plums and quite a few cherries. These trees need to be pollinated by another tree of the same fruit but not the same variety.  The two trees need to be in blossom at the same time.

Triploid trees  cannot pollinate themselves NOR another variety because their pollen is mostly sterile. The most well known triploid variety is Bramley.  

The trees pollinating one another need to be in the same area, but not necessarily very close, as the bees fly quite a long way when going about their business.

Pollination groups

For pollination to be successful the trees need to be flowering at the the same time. Each variety has a flowering period, which ranges from A (early) to E (late).

Because flowering is spread out over a few weeks varieties in adjacent groups make perfectly acceptable pollination partners because  the flowering periods overlap

Rootstock

Most trees grown for their fruit these days are grafted onto different rootstocks.  Rootstock trees are bred specifically for health and vigour, but also to control the size of the ultimate tree.

Varieties

So with all this cross pollination and grafting on how come we can be sure what our apple will be like?  The point to remember is that the roots just control the food supply to the tree, and that pollination only affects the next generatioin - i.e. the pip.  The actual apple is the basic tree’s response to having a pip, and, like the bark, leaves, shape etc will remain true to the tree type.

If you grow a tree from a pip you have no idea what will result - good or bad - and the word ‘pippin’ in the name often means that that variety was developed afresh from (no doubt one of very many) seedlings.

The only way to produce more trees of any one variety is to grow from a cutting - or more usually - by grafting.  The different rootstock only affects the size and vigour of the tree.

Source:  walcotnursery.co.uk/pollination.html

Fruit trees - Pollination