Q.My Japanese red maple is getting very thin
My tree is 30 to 40 years old, over 20 feet tall. I can see no sign of disease. It used to be when you would look up, the tree canopy would block out the sky. Now you see more sky than leaves. Is there anything I can do to restore my tree to its old form?

Certified GKH Gardening Expert
It is possible that it is declining due to old age, especially if it is a smaller variety of Japanese maple. Plants, like animals, have a lifespan and will die eventually no matter how well we care for them.
That being said, there are things it could be other than old age. It could be a fungus, a pest or lack of nutrients causing it to thin out. Treat the tree with a pesticide and an herbicide, like neem oil and fertilize with a nitrogen rich fertilizer. These will take care of a significant amount of what environmentally could be wrong with the tree.