Peat Moss as Organic Matter: Pros & Cons + When To Use It

Peat moss has been a source of controversy ever since it was introduced as a growing medium in gardens. The organic material is not sustainable as it takes millennia to form, and it releases a ton of carbon into the environment when mining it.

Still, peat moss has its fans who wouldn’t accept any alternative even the nutritious and more affordable compost.

Peat moss is used mainly to amend heavy soil by softening its texture and improving drainage. It’s an ideal growing medium for cultivating acid-loving plants such as tomatoes, heathers, and camellias among others. You can use it in combination with perlite for hydroponic growing. And as a sterile organic matter, it’s perfect for seed starting.

On the downside, there are environmental concerns about the impact of mining peat moss on the ecosystems surrounding peatland.

Read more to find out the advantages and disadvantages of using this precious resource.

What Is Peat Moss Made Of?

Peat moss is the decomposed sphagnum moss and other organic materials. The decomposition is natural and takes place in peat bogs in the absence of air. This is why it takes thousands of years to develop peatland worth mining.

On average peat moss adds a layer one millimeter thick per year.

Where Does Peat Moss Come From?

Peat bogs are the main source of peat moss. It’s mined out of peatland, processed, dried, then packaged. Since it doesn’t decompose fast enough, peat bogs get drained quickly. This is why peat moss is not a sustainable source.

Is Peat Moss Organic Matter?

As the product of sphagnum moss and other organic materials, peat moss is a precious organic matter that you can use to start seeds, in hydroponic growing, and to amend the heavy soil. 

What Is Organic Matter in Gardening?

Organic matter in gardening refers to materials derived from living things such as plants, animals, and other organisms.

Organic matter is divided into three categories:

  • Active Organic Matter: This is matter derived from plants and animal leftovers that are semi-decomposed. In a way, active organic matter is quite fresh and is teeming with microorganisms still processing the materials. This matter enriches the soil although the carbon and other nutrients are not readily available to the plants.
  • Slow Organic Matter: This organic matter is mostly animal parts such as bones that take a long time to decompose. Crushing the matter as is the case with bone meal helps speed up the decomposition and release the nutrients into the soil.
  • Passive Organic Matter: This matter is usually fully decomposed and has no active organisms. Often called ‘humus’, it’s the most often organic matter in gardening. The nutrients in this matter are readily available to the plants once you mix them into the soil.

Organic matter is added to the soil to improve its texture. If you want to amend clay soil to make it less compact or help sandy soil retain moisture, then organic matter is the ideal solution.

It’s also a good food source for the good bacteria and other microorganisms that enrich the soil. By adding organic matter to your garden soil, you increase the good organisms and reduce the number of pathogens.

Another benefit of organic matter is that it releases its nutrients directly into the soil for the roots to absorb. Unlike chemical fertilizers, organic matter doesn’t cause root burn or stress the plants with sudden growth spurts. It stays in the soil feeding the plants slowly for weeks on end.

Does Peat Moss Have Nutrients?

Peat moss has little if any nutrients that will benefit your plants in any meaningful way. Neither does it have any live microbes that could benefit the soil. The decomposition of sphagnum moss has happened over thousands of years without air so the microbes are long dead.

You should not use peat moss either as a fertilizer or a food plant supplement. You should continue to fertilize the plants regularly with your favorite fertilizers regardless of how much peat moss is in the soil.

Is Peat Moss Acidic?

Peat moss has low pH levels that average anything from 3.0 to 6.0. When adding it to the soil, make sure to test the soil pH regularly to make sure it doesn’t become too acidic for your plants.

Although peat moss loses some of that acidity over time as it mixes with other nutrients in the soil, its impact when freshly applied can be too strong for many plants.

Peat Moss vs. Coco Coir

Although both peat moss and coco coir are acidic organic materials, there are many differences between them. On average peat moss is considered the more acidic of the two options and adding it to the soil can increase its acidity drastically.

Coco coir averages between 5.5 to 6.3 which makes it safe to add to potting mixes without the need for limestone to neutralize the acidity.

But the high acidity of peat moss is why it’s a sterile matter while coco coir might harbor some microbes and pathogens. And even though both of them are good for holding up to 20 times their weight in water, coco coir retains the moisture much longer and releases it more slowly than peat moss. 

Another difference is in the cost. Peat moss is quite expensive compared to the more affordable coco coir. The price of peat moss is expected to rise as less and less of it remains in nature.

Peat Moss vs. Compost

If you had to choose between compost and peat moss, I would recommend compost. Compost is more cost-effective and highly nutritious compared to the pricey peat moss which has no nutritional value for the plants.

Not to mention that the sterile peat moss has no good bacteria at all. Compare that to compost which is alive with microorganisms that break down the organic matter in the soil and when they die they fertilize the soil with their decaying bodies.

Compost doesn’t change the soil’s pH which is more than can be said about peat moss. You don’t have to worry about adding too much compost to the plants. The only drawback about compost compared to peat moss is the smell. 

Peat Moss Benefits

There’s no denying that peat moss is a popular choice for gardeners in the US. Even though most of the peat moss available comes from Canada with all the environmental controversies surrounding it, the organic matter has many benefits to the soil.

  • It’s sterile which makes it ideal for seed growing and hydroponic growing.
  • It’s devoid of any chemicals that could change the structure of the soil or harm the plants.
  • Peat moss retains moisture for a long time and releases it slowly which helps with seed starting and potted plants where the soil dries out fast.
  • Use it to amend the soil and reduce its pH levels for acid-loving plants.
  • Peat moss is an ideal solution both for clay soil that compacts and sandy soil with low water retention. 

Peat Moss Disadvantages

But being a popular organic matter among gardeners doesn’t mean peat moss doesn’t have its downside. Here are some of these disadvantages.

  • Peat moss is not sustainable. It takes millennia for enough peat moss to decompose that is worth mining. 
  • Mining peat moss causes drastic changes in the ecosystem around the peat bogs. 
  • With its high acidity levels, peat moss can reduce the soil pH if added in large quantities.
  • Peat moss is quite expensive compared to compost.
  • It also has no nutrients or living microbes that could benefit the plants or the soil.

What Plants Like Peat Moss?

Plants that thrive in acidic soil would benefit the most from high doses of peat moss. These plants include strawberries, tomatoes, blueberries, azaleas, Pieris, heathers, and camellias.

Peat Moss for Indoor Plants

The main advantage peat moss offers to potted plants is that it holds water for a long period of time and releases it slowly. If the soil dries out fast during the summer months, mix it with peat moss to reduce the need to water the plants frequently. It’s also a sterile material with no odors which suits houseplants.

Is Peat Moss Good for Grass?

Peat moss improves the germination of grass seeds on the lawn and increases the aeration of the soil. Water retention is another benefit of adding peat moss to grass.

How Much Peat Moss To Add to Soil

For most plants that prefer slightly acidic soil, then mixing 1 part of peat moss with 2 parts of soil is a safe strategy. You might want to increase the peat moss quota in the potting mix for plants that crave more acidity.

Mixing Peat Moss With Soil

When mixing peat moss with the soil, always check the soil pH both before and after adding peat moss. The highly acidic peat moss can change the chemical structure of the soil making it unsuitable for many plants.

Peat Moss Alternative

If peat moss is either too pricey for you or you are concerned about the environmental footprint of mining this precious resource, then you can find more affordable and less controversial alternatives. Compost is by far the best alternative to peat moss, followed by coco coir, pine bark, rice hulls, and PittMoss.

Conclusion

Peat moss, as an organic matter, is a valuable addition to your garden soil. The sterile material is clean, doesn’t compact, and holds water 20 times its weight. It’s highly acidic so you should use it cautiously in the soil.

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