I know some fruit trees like apple, plum, cherry etc requires cross pollination for setting fruits.
Let's say I have only one tree and I can propagate a new tree by air layering. So the new tree and the existing one can cross pollination. Will that work?
I don't think that will work because the new tree and the existing tree are identical generically but I am not sure.
Please shed some light on.
Apples requires different varieties, and you should check online for the possible crossing. The reason: auto-pollination is avoided, and fruit plants are often clones, so they are the same tree.
The other plants are not so difficult as apple trees.
I think you are overthinking. The easier way: check other fruits tree "nearby". Ask the owner if you can get pruned branches (pruned branches as the trashed away part). Maybe the first time ask for many, and store some in cellar, and some directly under the tree. Many pruned branches tend to flower anyway. This could be enough to cross pollinate trees, and easy to do. You may use the cellar branches, if the cut one will flower too early. Move them into your (heated) home if they will not flower together to the trees.
You may try also pollinate yourself the trees: with a brush (with the above branches).
