QuestionsHow to growVegetable GrowingPotatoespotatoes 0 Vote Up Vote Down James Byrne asked 15 years ago potatos are up about 6 inchs when do i start to earth them and spray for blight? 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 7 years ago Earthing up can be done a couple of times, or once to save effort. Earth up before the leaf canopy meets over the rows. Spray for blight when the Met Eireann warnings are given.