Empty Walnut Shell

Question

No nut inside black walnut shell

Answer 1

They probably aren't all empty. Unfinished nuts will drop from the tree. Green fruits that drop are not mature. Fully ripe nuts are a yellow to tan color. Empty nuts are often due to poor pollination. The shells are still produced, just empty ones.

https://www.gardeningknowhow.com/edible/nut-trees/black-walnut/harvesting-black-walnuts.htm

https://www.gardeningknowhow.com/edible/nut-trees/general-nut-care/nut-tree-fertilizer.htm