It's a mulberry, not a blackberry. They are edible but taste nothing like a blackberry and I find them quite bland. They are also very weedy and you will find seedings popping up all over where there a fruiting mulberry around.

Thank you so much!

They actually taste similar to a black raspberry imo. They are a very sweet and under appreciated fruit. Some people love them, some don't. If you have a tree that produces tasty fruit, why not try making some homemade jam? :)

Fallen fruit from the trees will stain any solid surface.

Mulberry juice can be found at some grocers.