I have many of morus alba, I presume. I also have one that's completely different in the respect that it has completely smooth leaves (both sides, and in all directions) . Most of the mulberries here are like very fine sandpaper on the top of the leaf, and only when rubbed upward toward the petiole. The bottom side of the leaf is rough due only to raised veining, no hairs or overt fuzziness. This other one is completely smooth and the leaves are all uniformly the same in regard to shape and size, not variant as in the others. The trunk is grayer than the others as well; they're more of the typical orange-gray. Could this really be a paper mulberry? Surviving and fruiting every summer (late June through the end of August) in zone 5?
[I have pix of this tree, I just can't load them right now as my connection today is way too slow.]
