As I have typed before, any one squirrel will eat any one thing during any one year. To me it would be unusual that squirrels would feast on apple flower buds every year over a 20-year period. Must be a learned tradition of your local tribe of squirrels. Extensive trapping for a year or two might break the tradition.

If your tree is isolated enough from nearby plants and structures, it is possible to use defensive measures around the trunk.

It may not be just the squirrels causing the lack of apples. Is there another apple tree close by to offer cross pollination? Apples need a pollination partner to properly fertilize the blossoms (any left by squirrels :-)) to produce fruit but will occasionally generate a few anyway. Even so-called self-fertile varieties will crop better when provided with another apple variety for cross pollination purposes.

Yes, for the rodents to be the cause the tree needs to be getting stripped of flowers every year. Is that what you are being left with each time, an effectively flowerless tree? If instead - as would be expected - a number of flowers are surviving their attentions then the suggested lack of fertilization of the flowers by the pollen of another, compatible apple cultivar, random apple seedling or flowering crab-apple would be the assumed problem.

Otherwise inadequate soil fertility may be possible - in one instance of a barren commercial orchard in New York the cause was determined to be a nitrogen deficiency. Nitrogen is the one primary nutrient believed to be frequently lacking in local gardened soils.

I should not have said 'no' apples. (It is a Gravenstein, if that makes any difference.) It blooms profusely, but I have been checking this year, and the blooms have disappeared. There are a few that have been pollinated and have the start of an apple, but only an average of one per branch. I do get a few apples, but many are too small to do anything with. Most hide from me and then fall off before they're ripe and have been bitten into (by squirrels?). Both of my next-door neighbors have apple trees. One is very old and makes almost no apples while the other gets a full crop. I'll add more nitrogen and see if that helps. Thanks so much for all the feedback.

Gravensteins are my all-time favorite apple and the only type I've grown personally. They tend to be biennial producers, producing decent crops only in alternate years with very sparse production in the off years. This could be an 'off' year :-)

'Gravenstein' is mentioned as an example when discussing apple cultivars that have sterile pollen, can therefore not fertilize either themselves or any other cultivars. Identifying and planting a suitable pollinator for your 'Gravenstein' may solve your problem - the apples nearby may not be the right ones. Nurseries stocking fruit trees and web sites discussing them have pollination charts showing which varieties fertilize one another.

You only need overlapping bloom times for another apple to be an appropriate pollinator........unless one is another triploid variety (sterile pollen). Gravensteins tend to have a rather early bloom period but also a long one and sometimes even push a second, later set of blossoms. Generally any of the early to midseason bloomers should suffice and that inlcudes most flowering crabapples.

If you want to ensure proper cross pollination and not rely on what the neighbors may be growing, any of the columnar apples (North Pole, Golden Sentinel, Scarlet Sentinel) will provide the service, plus are small enough to squeeze into any garden.