I thank you for that post for I knew nothing about this & have a few small Black Walnut trees that had sprung up within 30ft, of my pond & was going to leave them there to grow. I had even considered planting a few for there are tons of nuts right in my yard every year & the seedings spring up everywhere each spring. Black Walnut trees are abundant in my area. I will keep this info in mind from now on. I dont think those small walnut trees will be growing there much longer.
