I've heard you can't grow tomatoes within 30 feet of a black walnut tree. We planted blueberry plants about 20 feet from one and they just didn't grow. I have two Pecan trees I'd like to plant on the same side of the house as the Black Walnut, but I don't want to lose them. Am I safe to plant them near this tree? If so, how far away from the Black Walnut should I plant the other trees?