QuestionsHow to growTrees and ShrubsWeedsweed that looks like seaweed 0 Vote Up Vote Down Una Grant asked 15 years ago My mother has a greenlike seaweed appearing all over her drive. what is it and how can it be treated 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago This is either a moss or alga or possibly lichen. Mosgo or similar product will clear any of these.