Q.Black heart cherry tree
My tree is about 25 years old. Early summer all the leave began to turn and fall off.
It bloomed very well in the spring. Now here in October the leaves are coming back
And it is blooming again. I live close to Greensboro N C. What made it do this?
Thanks
David Stewart

Xanthomonas bacterial spot of cherry and Blumeriella leaf spot of cherry can both cause leaf loss, as described here:
https://ask.extension.org/questions/207426
https://extension.umd.edu/hgic/cherry-shot-hole-flowering-cherries
http://www.extension.umn.edu/garden/yard-garden/fruit/integrated-pest-management-for-home-stone-fruit-growers/cherry-leaf-spot/
These diseases would have caused spots or holes in the leaves to form before they fell off. Overwatering or other environmental stresses could also cause leaf drop.
The good news is that since your tree is producing leaves and flowers again, it will probably return to health. Some cherry varieties normally do bloom twice a year, but if yours hasn't done that before, it may be some sort of stress reaction.