Primary Decomposers These saprophytes are typically the first to grow on a twig, a blade of grass, a chip of wood, a log, a stump, or a dead insect or other animal. Primary decomposers are typically fast growing, sending out rapidly extending strands of mycelium that quickly attach to and decompose plant tissue. These woodland species include oyster mushrooms (Pleurotus species), shiitake (Lentinula edodes), and maitake (Grifola frondosa).