Hallo. I used to own a Black Knight Buddleia. I still have the plant but it has faded over the years to a more usual purple. My theory is that it was grafted on to standard buddleia rootstock and successive prunings cut away the black knight grafts. I want a white buddleia and I'm terrified of the same thing happening, cutting it back over years and gradually losing the white to usual purple. I've looked online trying to find out if the various white types are actually grafts but with no real success. I did read that buddleias can change colour depending on site and my mauve one is south facing and gets sun in the morning. I'm planning to plant this new one south facing in my back garden and it will get full sun late morning and all afternoon. If it is a graft issue, can you advise on the best white buddleia that wil stay white?