I guess it’s only dirty considering where you plant it.
I had my Aunt in Green Bay, Wisconsin send me some of their native Black Walnuts about 30 years ago (I currently live in northern California).
The ones I planted out on the mountain side haven’t done very well but the ones I planted down by the spring and in the creek bottom are doing great.
I found they are not nattracive trees.
We had some on our property in NY. THey leafed out late, dropped their leaves early in the fall, and produced walnuts irregularly. Some years were great, others not. And when they were dropping walnuts, it was almost impossible to mow without getting clonked on the head with walnuts and then there was the stepping on them factor when you were mowing.
They do not make a good landscape tree, but their wood is highly valuable and the nuts are worth the effort to harvest. They are a good tree to plant in the wild.