we have had apple, plum and pear trees on our allotment for 3 years now but never had any fruit on the plum and pear trees. There are other plum /pear trees on other plots close to ours. What could we be doing wrong.
It's more likely frost problems which either kill the flowers before they've been pollinated or else make it too cold for the pollinators to fly and visit your blossom.
If the other trees are producing fruit it may just be that they flower at a slightly different time and escape frost problems or else they have other pollinator plants around them to attract the insects to lurk in their corner rather than yours. Try under planting yours with bulbs and early spring flowers which will provide pollen and nectar to feed the pollinators and entice them towards your fruit trees.
A mahonia shrub will provide food over winter and early spring and then snowdrops, crocuses, hellebores and narcissus will continue the food supply and encourage pollinators to hang about for your fruit trees.
Thanks obelixx. I'll be trying that for sure. Thanks again