Most mosses grow only 1/4 inch to 2 inches tall. A mat of moss consists of thousands of tiny plants that attach themselves to the soil and absorb nutrients through rootlike structures. Liverworts grow in thin, lobed sheets along the ground. Algae are simple, freshwater plants that thrive in frequently wet conditions. Algae may be found growing on wet, compacted soil that is high in nitrogen and organic matter. Both mosses and liverworts grow best in moist, shady areas with acid soil. In cultivated gardens and lawns, they indicate excess acidity, poor fertility, overwatering, or poor drainage or aeration.
You may remove mosses and liverworts from lawns and gardens by hand-raking. Reduce shade by pruning nearby trees. Improve soil fertility with regular fertilization, and improve soil drainage. Correct pH if necessary. Prevent algae from returning by reducing soil compaction and pruning nearby vegetation to reduce shading.