A method of refining wheat straw into fibers cuts the straw to a length of between about two and about four inches, wets the straw, softens the straw by subjecting the straw to pressurized steam and refines the softened straw in a pressurized mechanical refiner to produce fibers capable of being used in the manufacture of cellulosic board products. The straw fibers may be combined in any proportion to other fibers, such as wood fibers, and used in known dry, wet-dry, and wet board manufacturing processes to produce softboard, medium-density fiberboard, and hardboard products.