posted 12 years ago
I'm not 100% positive but using black walnut leaves could possibly suppress the growth as long as the species growing near your fence aren't tolerant to Juglone (the chemical that is responsible for the suppression effect).
I have read that all other members of the walnut family do contain juglone but at much lower concentrations then the Black Walnut, so I don't think the English Walnut would work as toxicity is rarely encountered around the other walnuts.