Why Does My Sour Cheery Tree Still Have Green Leaves Attached?

Question

this tree had no fruit this year

Answer 1

When leaves fail to drop, it's usually weather related. It also can be due to excess nitrogen. These articles should help:
https://www.gardeningknowhow.com/ornamental/trees/tgen/why-leaves-did-not-fall-off-tree.htm
https://www.gardeningknowhow.com/edible/fruits/cherry/when-to-fertilize-cherry-trees.htm
https://www.gardeningknowhow.com/edible/fruits/cherry/cherry-tree-not-fruiting.htm