Mulching with Fruitless Mulberry Leaves?

[Denise4Peace]

I had a fruitless mulberry in my backyard for over twenty years. It was old and big when I bought the property twenty years ago. It died last summer, leaving behind about a foot and a half (at least!) of leaf mould and pushed-up dirt. I want to plant other trees and plants in my backyard. I also have a garden plot where I'd like to dispense with some of the organic material it left behind, to level the yard.
However, I haven't been able to determine if the leaves, etc., are toxic or hostile to other plants. Nothing else grew under that tree. Nuthin'!
Is it advisable to use the built-up leaf mould as mulch in my vegetable garden?
If not, how can I amend the soil in my backyard to be more encouraging to new plantings?
Thanks for any assistance!

[Dirt Doctor]

No problem using the leaf mold. Reason nothing was growing under the mulberry was the heavy shade.