Sawdust is often used as a mulch material around herbaceous perennials and woody ornamentals. Problems can occur as sawdust starts decomposing. Soil bacteria may tie- up or "borrow temporarily" some available nitrogen. The constant addition of sawdust may cause plants to appear stunted and yellowish. As the sawdust finishes decomposing, nitrogen will be returned to the soil.A handful of a complete fertilizer scattered over the sawdust should limit any temporary nitrogen depletion.