Poplar burns fine. Make sure it isn't green. We tend to mix woods together when we're firing. A few large pieces of poplar, one or two medium pieces of pine to really get her going and a few small pieces of birch or maple to give a good sustained heat and lay down a good bed of coals. We throw in a piece of spruce now and then also.We split up old barnboards into small pieces and throw 2-4 of them in at a time when we're finishing off. Basically if it makes the sap boil and almost jump out of the pan-use it!!