Unfortunately, the messy black walnuts are just part of owning a black walnut tree. We had an older black walnut tree that appeared to be very distressed and we needed to cut down. We had heard from a friend that they had sold their black walnut tree and actually made money. When we checked with our local tree surgeon, though, he wasn't too interested in taking down our tree in a residential neighborhood for recovering the wood (with some fear that nails or other items had been driven into the tree over the years). If you're looking to keep the tree, nevermind - but if you're in a position to remove and replace, this might work out for you..