Answer: Unfortunately, the pollen from the plum tree will have no effect on an apple tree. Your tree will need another, different kind of apple tree as pollen source. It will need to bloom at the same time as your apple tree. Usually insects (bees) take care of moving the pollen for you, so you don't need to worry about using a cotton swab to help out. You would not expect to see fruit until after the blossoms are finished. An apple will form at the site of each flower, assuming pollination occurred. You will see tiny little apples on the tree. Eventually they will grow large and turn color in the fall when they ripen. Whether or not you need to supply another tree or not depends on if there are other apples (or even a crab apple tree) in the area that bloom at the same time as yours does. You could wait and see what happens this year, then you will know if you need to plant a pollen source for your tree or not. If you need to, it will be helpful to know the name of the apple you already have and then the nurseryman (or possibly your county extension) can direct you to a suitable apple variety. Here is some general information about growing apples for home gardeners in North Carolina that you may find helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Enjoy your new tree!
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