QuestionsHow to growVegetable GrowingWeeds, Pests and DiseasesWeedkiller 0 Vote Up Vote Down Kieran Darling asked 15 years ago Please advise suitable total weedkiller for use around outside around polytunnel. 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago Roundup can be safely used but it must not be allowed to drift onto non-target plants.