So we have a major problem with vincia aka: periwinkle, so this is one reason our chickens cannot free range, periwinkle will kill them and goats. I have been searching online all morning of a way to get rid of this stuff, preferably an organic way, but there are none. So in my lengthy seach all of the answers keep coming back Round Up. As much as I don't want to use the stuff, it looks like I am going to have to. So I have a question. How long after the Round Up is applied (there will be at least 4 applications along with pulling the periwinkle by hand) can we let our girls over in that area? We will put down grass seed almost emediately (sp?).