Hi Crystal, you can buy the collors, like almost anything if you are prepared to pay the price, on my site a guy just cuts a square of stiff fabric, cuts centre out and then a slit from outer edge to centre making it possible to slip round the stem, but I have heard of people using roof felt, not sure about cardboard I would think you would have to keep it moist to ensure contact with the soil but hopefully Tee Gee or one of the other experienced guys will be along soon to offer other ideas.