Pros & Cons of Peat Moss

Dried bricks of peat moss expand when moistened.

Dried bricks of peat moss expand when moistened.

Soil amendments provide nutrients or improve the quality of a garden bed. Peat moss, usually sold in bales or bricks, is used to improve both the soil in beds and in planters. Peat isn't suitable for every plant or garden soil need, so an understanding of the pros and cons of this amendment helps you make an informed choice when improving your soil.

Pro: Soil Quality

Peat moss improves the quality of garden and potting soil. It resists compaction and so provides aeration to soil beds, a necessity in heavy soils that otherwise would hold too much water instead of draining properly. Although peat moss aids drainage, it also absorbs moisture so the soil doesn't dry out too quickly. Peat has a high acid content, which helps healthy growth on acid-loving plants such as blueberries, but it will require lime amendments when used in vegetable gardens and other locations with plants that can't tolerate a high-acid environment.

Con: Cost

Compared to other soil amendments peat moss is an expensive choice for the garden. Peat isn't a local resource and is generally shipped from peat bogs in Canada, which adds to the cost. A small amount used for potting soil is more cost-effective than attempting to amend an entire bed with peat moss. Although costlier, peat moss doesn't break down quickly in the soil, so it doesn't require frequent replacement. A peat application can help garden soil for two years or more, allowing you to spread the cost out over time compared to amendments that require annual applications.

Pro: Seed Starting

Unlike compost and soil, peat moss is completely sterile and harbors no disease organisms and rarely contains weeds or pests. This sterility makes it an optimum choice for starting seeds. Seedlings are particularly susceptible to fungal diseases that cause death. Fungi can't usually survive in peat. Peat also absorbs water slowly, which can prevent overly soggy soil that causes seeds and seedlings to rot. This same attribute can make it difficult to moisten if it's allowed to dry out completely, so proper watering practices must be followed when starting seeds in a peat-based soil mix.

Con: Sustainability

Sustainability issues surround the harvesting of peat moss. It only grows in a few areas worldwide where peat bogs can survive. Peat moss grows slowly from sphagnum moss debris that decompose in an oxygen-free environment beneath the water in a peat bog, and it takes many years for the moss to turn into peat and renew the source. Careful peat mining works to minimize the environmental impact of peat harvesting so that the resource isn't depleted, but other more renewable options, such as coconut coir, are sometimes preferred over peat.

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