Peat Moss to Water Ratio

Sphagnum Peat Moss

• There are more than 500 species of moss in the Sphagnum genus. Living sphagnum moss floats on water so it can get sun for photosynthesis. Its cells soak up water from which the moss gets its nutrients. Sphagnum peat moss is the layer of dead cells just underneath the living sphagnum moss. These dead cells can soak from 15 to 20 times their weight in water. This is the peat moss commonly available in garden center stores and is the best for soil amendments and planting mixes. The Canadian Sphagnum Peat Moss Association requires that peat moss marketed as sphagnum peat moss have more than 66 percent of its fiber from the genus Sphagnum.

Hypnum Peat Moss

• Many peat mosses harvested in Northern U.S. states are composed of mosses belonging to the Hyypum genus. Hypnum peat moss decomposes faster than sphagnum peat moss, but you can use it to successfully grow plants. Studies show that hypnum peat moss can hold 12 to 18 times its weight in water. Hypnum peat moss must contain at least 33 percent fiber, half of which must come from the Hypnum genus.

Reed-Sedge Peat

• Reed-sedge peat are mixes of moderately decomposed coarse grasses, reeds, rushes and sedges. This form of peat can hold from 4 to 12 times its weight in water. It must have at least 33 percent fiber with at least half coming from reeds, sedges and other non-moss plants. Reed-sedge peat is not considered good for horticultural use.

Humus Peat

• The decomposed debris of many undisclosed plants is sometimes sold as humus peat. Humus peat often contains particles of clay and silt. Although this peat can hold from 1½ to 5 times its weight in water, it decays rapidly and is not considered good for planting mixes.