The spores of the slime mold survive in soil or organic debris and germinate during wet weather to form motile swarm spores. Some of these spores fuse to become amorphous amoeba-like structures that engulf other organisms or organic matter. Slime molds can actually move or flow across soil or plant surfaces. Although unsightly, these organisms are not pathogenic to living plant material. Frequent mowing, raking, or brushing of the spore masses is usually sufficient to control the problem.
Many different mushrooms can also appear in lawns.
Some of these mushrooms are associated with arc-like or circular patterns in turfgrass called fairy rings. The ring pattern is caused by the outward growth of fungal mycelium. The mycelium forms a dense, mat-like structure in the soil that decomposes organic matter. This decomposition releases nitrate into the soil, which in turn stimulates the growth of the grass at the outer portion of the ring. This results in a dark green appearance of the grass at the margin of the ring.