I reviewed the info provided on rhubarb which states that the leaves are poisonous, and part of the reason that deer don't eat them. Question 1: Is it possible to cook the leaves so it makes a natural herbicide? I would like to kill some invasive plants (neighbors!) to prevent them from getting into my garden. Question 2: Also, because of the oxalic acid, how far away should the rhubarb plant be from the rest of my garden? My dad had this plant at least 30 feet away from our previous garden. Can rhubarb affect other nearby plants, and stunt their growth or kill them? Question 3: I've also heard that chestnut trees are not good to grow near also. Is that because it also has oxalic acid?