Although the warm start to the year initially raised hopes of a good harvest, frosts in April and cold rainy weather in May and June reduced pollination and led to losses of remaining fruitlets. This will mean poorer plum crops this summer and a dearth of apples and pears later, says the RHS.
The charity suggests that to preserve whatever crop is left, it's important to keep down weeds around trees, so that there is less competition for nutrients, especially in dry spells.
Careful control of pests and diseases will also help and there will be little need to thin out the remaining fruit.
Gardeners should summer-prune restricted forms of fruit trees such as cordons and espaliers. With few fruits to support, it's likely that trees will grow too many branches and leaves.
"Because trees have dropped quite a lot of their developing fruits, gardeners should be wary about thinning fruits - and in many cases not thin out at all this year," says Guy Barter, RHS chief horticultural adviser.
"This current warm, moist weather, in the absence of a heavy fruit crop, will also encourage lush growth, so summer pruning will help direct nutrients to the fruit and promote productivity for 2013.
"Adding potassium (high potash) fertiliser to the weed-free area at the base of the tree can help harden growth and promote fruitfulness."