I INHERITED A SITE/GARDEN WITH SOME APPLE TREES UPON IT ,I AM TOLD THAT THEY PROBABLY GREW FROM SEEDS THAT WeRE THROWN OUT ABOUT 40 YEARS AGO . LAST YEAR I PLANTED 2 NEW APPLE TREES ALONGSIDE THE OLD ONES. THERE WAS PLENTY OF FRUIT LAST SEPT/OCT BUT THIS YEAR I HAVE NONE. SHOULD I REMOVE THE OLD TREES AND PLANT ALL NEW YOUNG TREES?
The young trees may stop fruiting for a year or two if they are growing well. Old trees can be productive if they are fertilized and pruned a little each winter. Thye may also need to be sprayed to control apple scab if there are spots on the fruit.
More information in Know-how: How to grow: Fruit: Apples