I planted a Nectarine (Independence) tree in February, 08. By April it was loaded with flowers and I picked many off before they fruited. I figured a sapling this size couldn't handle that many normal nectarines. Still, there were tons of flowers remaining. I let them go to fruit and all the nectarines were smaller than apricots and ripened at that size. What happened? I never saw anything like this. I watered mostly daily by filling up the landscape mound with water as I do for all of my trees. They are in full sun.
Interestingly enough, I planted a Peach next to the Nectarine and the peach got a few flowers, but only ended up with TWO peaches that are growing to normal size. I also planted an Almond, but in the front of the house and that too was loaded with fruit--well nuts, but they grew to normal size.