What Is Peat?

Peat is a fibrous material formed by the slow decomposition of organic matter. When processed as a gardening medium, this product is often referred to as peat moss, as peat is made primarily from decomposed moss. However, the actual composition of peat varies.

In some instances, peat is an early stage in the formation of coal. If the peat is buried under 4 to 6 feet of sediment and subjected to an increasing amount of heat and pressure, it may form lignite.

Peat has four primary characteristics that differentiate it from other lower-ranked coals. It is:

• Free from cellulose.
• Over 75% moisture.
• Less than 60% carbon.
• Soft enough to cut with a knife.

What Is Peat Soil Made Of?

Decomposed sphagnum moss is the primary component of most peat soil found in the United States. However, you shouldn’t confuse this soil with sphagnum moss itself. Sphagnum moss is a fibrous plant material available in long strands. It is often used to line hanging baskets or make craft projects.

Some types of peat are derived from plants other than sphagnum moss. Peat that comes from the lowland humid tropics is made from decomposed trees in the rainforest. Peat from New Zealand is comprised of restiads, which are flowering rush-like plants. In tropical climates, peat is sometimes formed from decomposed mangroves.

How Is Peat Formed?

Peat typically forms in bogs. This material requires a waterlogged environment with few nutrients, an absence of free oxygen, and high acidity. These harsh conditions contribute to the slow formation of peat, which is mostly made of decomposed plant matter. Without the presence of air, decomposition takes thousands of years. This is why composters purposefully aerate their compost bins.

Peat bogs gain less than 1 millimeter of depth a year, so this is a slowly renewable resource. To maintain the potential for long-term peat harvesting, peat must be handled carefully. Overharvesting in Europe has caused some peat wetlands to sustain serious damage or disappear entirely. However, in Canada, mindful practices are in place, which allows the peat to replenish faster than it’s harvested. While 70 million tons of peat are created each year in Canada, just one million tons are harvested.

How Is Peat Processed?

Traditionally, peat has been hand-cut using spades or hoes to create blocks. These blocks are pressed to remove water. The peat blocks are dried further using pressure or heat until hard bricks remain.

Alternately, large machinery can be used for modern peat harvesting. An excavator or dredger collects peat from the surface of the bog. A macerator soaks and separates the peat to remove the pulp. This pulp is then dried and cut into dense blocks.

Where Does Peat Come From?

Most of the world’s peat comes from wetlands and bogs in the northern hemisphere. These peat bogs cover approximately 1 billion acres or 2% of land on Earth. Two-thirds of this supply is in Russia and a quarter is in Canada. Peat bogs are also found in areas of Germany, Sweden, Finland, Ireland, and Scotland. The British Isles and Scandinavia have large peat bogs as well. 

What Is Peat Used For?

Peat is most commonly known as a gardening medium, but it wasn’t used in horticulture until the 1940s. Prior to that time, peat was a popular source of fuel. It can serve as an alternative to firewood for home heating and boiler firing. Some use it as a fuel source for home cooking as well. Russia, Ireland, Finland, and Sweden use peat for electrical generation. In Finland and Sweden, peat-burning stations provide hot water and steam too.

Today, peat is often used as a soil amendment. Its versatility makes it helpful in many different conditions. Peat can help sandy soils retain more moisture, while it increases water infiltration in clay soil. Peat moss is free from the weed seeds and microorganisms that are often problematic in compost, so it’s a very clean choice for your garden. It retains nutrients as well as it retains water, so it will feed your plants well. You can find peat starter pots, peat pellets, and peat soils. 

Peat increases the acidity of soil, so it is often mixed with lime to counteract this effect. Gardeners also commonly blend peat moss and compost to make a well-balanced soil amendment for gardens or raised beds.

Considerations for Using Peat

Peat moss is an excellent soil amendment, but there are some important things that gardeners should take into consideration when using this product. Some conservationists warn against the heavy use of peat because peat disturbancecan:

• Release large amounts of carbon dioxide into the air during and after mining.
• Cause a decline in biodiversity by disrupting complex habitats.
• Release peat particles and dissolved organic matter in surface waters.
• Make the remaining topsoil from the bogs susceptible to wind and water erosion.
• Create a landscape that’s susceptible to peat fires.

When peat is harvested slowly and responsibly, however, many of these concerns are mitigated. 

Peat moss will last for years in your garden, so you don’t need to invest in a new application each year. Peat is best in gardens with acid-loving plants like camellias and blueberries. If your plants prefer a very alkaline soil, you should minimize your use of peat. A similar alternative is coconut coir. Coir has a nearly neutral pH between 5.8 and 6.8, which is more favorable for some plants. Coir also helps with water management in sandy and clay soils.

Peat is a very useful resource, but one that should be managed carefully. Used sparingly and harvested wisely, peat is something that we can continue to benefit from long into the future.