Peat moss has long been a favorite soil amendment and a key ingredient of "soilless" mixes for container plants. But peat harvesting and its effect on the environment have raised concerns.
All peat comes from wetlands or bogs, but there are big differences in kinds of peat and kinds of bogs.
Sedge peat, often sold loose in bags, is usually harvested from marshes, mountain fens, and other sensitive wetlands in the United States. Harvesting from these small and often environmentally fragile wetlands is a concern around the country.
The other kind of peat is milled sphagnum moss. It's far more common and is the most desirable kind for soil mixes and amendments. In soil mixes, its water retention is superior, and as a soil amendment it's much longer lasting. Sphagnum moss is harvested primarily from 40,000 acres (out of more than 200 million acres) of bogs in Canada, where regulations require sustainable methods. Although about 20 million bales of the tightly packed peat are sold each year, the bogs are so extensive that less than 1 percent of the total is harvested annually. Within five years after a section is harvested, the sphagnum moss is growing again and the bog is restored to functioning peatlands. Nevertheless, the mining of wild lands for peat moss makes some gardeners uncomfortable.
Our recommendation? Avoid bagged sedge peat altogether. Use sphagnum moss with care where and when necessary. Or, consider coir, a peat alternative. Coir is the fibrous material left after harvest and processing of coconuts. In tropical regions it's a common soil amendment. Coir looks and feels similar to milled sphagnum moss, and it loosens the soil just as well. Surprisingly, its water-holding capacity is superior to that of sphagnum moss, it's less prone to crust over, and it's easier to rewet when dry. Unlike peat, coir contains chlorine and potassium salts, which need to be flushed out by soaking in water before using with seeds or seedlings. Coir is widely available in compressed bricks and is slightly more expensive than sphagnum moss.