I know to regard my PFAs as maincroppers and they are showing the first signs that the tops are beginning to die (either that or blight has just struck ;)). I'm wondering, tho', whether it's necessary to cut back the tops and leave for a week or two to allow the skins to set, given that they are a 'salad' potato? And/or should I wait till the haulms have fully died back before harvesting?