Roundup herbicide from our friends at the 'sustainable' Monsanto is used to knock down weeds around trees and buildings on many farms. Ours is not one of them. We keep the weeds at bay with trusty weed whackers. Now these are not the most environmentally sustainable machines. So herbicides or gasoline? Roundup is made from Glyphosphate, a sugar, the problem is all the additives that they add to make the herbicide work well. There are some organic herbicides coming available which I hope to try soon. In the meantime we will keep whacking the weeds.