peat moss

or sphagnum

Any of more than 150–300 species of plants that make up the bryophyte genus Sphagnum, which grow in dense clumps around ponds, in swamps and bogs, on moist, acid cliffs, and on lakeshores from tropical to subpolar regions. These pale-green to deep-red plants can hold 20 times their weight in water. As they die and are compressed, they form organic peat, which is harvested and dried as fuel, as seedbed cover, and as shipping packaging for plants and live aquatic animals. Gardeners stir peat into soil to increase soil moisture, porosity, and acidity and to reduce erosion.

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