QuestionsHow to growTrees and ShrubsWeedsSt John wort (removal) 0 Vote Up Vote Down Stuart Coleman asked 13 years ago I bought a old property. St John wort is rampant is the garden how do i clear it successfully? 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago Cut it down with a brushcutter, allow it to re-sprout and then spray with Roundup, as directed.