There are a lot causes why plum and cherry don’t give the fruit. The stone- fruit trees bloom usually in early spring. Of this period the days are often cool, frost, that’s why the pollinating insects do not fly. And you should have the lines of several varieties of cherries, it would be better there were cherries – they are well – pollinate each other. The plums are good pollinated with varieties of cherry plums.
Secondly, it may be, in your trees the crowns is thickened, and they can not “survive” a great harvest, so that they reset the ovary.You should cut out the unnecessary branches and shoots. Each leaf of the tree has to ” swim ” in the sun.
It may be that there are no some microelements of the plants. You have to make the analysis of the soil and make fertilizer for the trees that haven’t it.
The another reason is the diseases and pests. Now, for example, the monilia damages the stone fruit trees. This disease is very special. The fungus gets through to the flower stalk, and then in the branch. As a rule,the adults cherry suffer the most, which bloomed in the rain – the whole ovary fall. So that we don’t see this disease next year, you should cut off the dry branches, and the leaves and fruits of infected fungus gather and burn.
As for the trees, which seems the youth and give a small harvest, then obviously that grow apple trees and pear on dwarf or half dwarf rootstocks. They are designed for gardens of intensive type. Their productive age – 10-12 years. Then, the harvest sharply fall. Such trees should be uprooted and we need to plant a new garden.