Q.Mulberry tree
My tree was fine and got the usual leaves. It is over 50 years old and huge. Suddenly the green leaves are falling this summer. We did go through a 5 year drought. What can I do.
Mulberry Trees can drop leaves if they are stressed; drought would certainly fall into that reason. Heavy rains or wet soil also can be a reason for leaf drop.
Watch for other signs of issues; pests, leaf markings etc.
https://www.gardeningknowhow.com/ornamental/trees/fruitless-mulberry/possible-causes-of-a-fruitless-mulberry-with-yellow-leaves.htm
https://www.gardeningknowhow.com/ornamental/trees/fruitless-mulberry/how-to-grow-mulberry-trees.htm