it is my understanding that you need 2 different varieties for polination. but that said, to get both to bloom,, i had some trouble with the less vigorous of mine to have enough flowers to overlap with the more robust one. i fertized with blue berry / azalea fertilizer last spring and fall, and again this spring, and they are both loaded. dont know if that did it, but i'm going with it. if you can locate another tree (wild, botanical garden, etc) get a flower from it with ripe pollen and hand polinate. its pretty easy to tell which flowers will be receptive