MC, I use straw, along with leaves and grass clippings, but during the winter, it's primarily straw. I like it. it definitely keeps things warmer and drier. it decomposes well, the top layer gets stiff if you don't dig it out before summer, but the soil underneath is incredible! I waited too long to clean it out last year, but the pitchfork made it easy... it's interesting how different groups do their housekeeping - the dome is nice and kicked around, well mixed. the Fosters have deep sections and bare sections. if I move straw to the bare sections, they clean it up and make the deep sections deeper. the Group of Seven banty boys have a perfect, smooth floor, made of almost a foot of straw, with one tiny open spot for a bath. I just put a big block of straw inside, I put 2 in the Fosters because they have 2 "rooms". they do all the work of spreading and keep it the way they want. as soon as the temps stay above 40° I will start to clean out the dome. the back pens can wait longer, more because the dome is shorter and I can't stand up straight inside when it gets to the end of winter and there are 4-5 extra bales accumulated inside. the back pen is 6' tall with peaked roofs.
