One thing about fertilizing fruit trees, it takes potassium to grow fruit and the nitrogen to grow broader leaves. If you want bigger fruits go with a 5-10-15 instead of a 10-10-10.
http://www.clemson.edu/extension/hgic/plants/vegetables/tree_fruits_nuts/hgic1351.html Here is what we use, pretty simple and straightforward with a lot of other useful information!
if you get these trees MAKE SURE you talk with a pro because you need a male and female or you have wasted whatever money you spent because they will not produce...same with plum trees
I've got 4 Persimmons on the way. Couple questions: What soils do they thrive in? Well drained? Also- how closely should they be planted in order to ensure cross pollination?