Differences Between Peat Humus and Peat Moss

You are perhaps pondering to prepare your own soil and you heard about peat humus and peat moss? In my experience, as a gardener, I came across these words often, so here what I know about it.

Despite peat moss and peat humus are both originated in a peat bog they are different. Peat moss is partially decayed organic material (Sphagnum) found on top of peat bogs. Differently, peat humus, presents totally (not partially) decayed organic material and it is found at the bottom of peat bogs.

Now that you know the differences among them you might be curious about how their features and how they affect your plant growth. For more let’s keep reading!

Peat Humus And Peat Moss: Different Origins And Characteristics

Peat moss and peat humus share the same “peat” component in their name because they can both found in peat bogs and they both contain decayed peat Sphagnum moss (a very specific type of moss). However, different proportion and state of decomposition play a key difference among them.

Peat Moss is given entirely by Sphagnum moss at a different level of decomposition  (but in general not totally decomposed) while peat humus contains a mix of decayed organic matter (other types of plants and animals) and highly decayed Sphagnum moss (way more than in peat moss). Indeed, peat humus is found at the bottom of peat bogs as it is the oldest material in the pot bog and, hence, with the largest time to decompose.

The different levels of decay is reflected in the differences of physical and chemical properties between the two medium (more info on the physical and chemical properties definition in 2 Aspects For The Best Potting Soils and DIY Recipe).

Peat humus is darker in color, denser, and finer in texture when compared to peat moss. At the chemical level, given that peat humus has undergone a heavier decaying it has: 1) a poorer nutrients-content and 2) a lower ability to retain water. 

Peat hummus is also more expensive than peat moss. This is because is a more scarce resource and takes even longer to form.

When To Use Peat Moss and When Peat Humus?

Peat moss has a wider application than peat humus. This is because peat moss has a combination of interesting chemical and physical properties (airy structure with the important ability to retain large amounts of moisture) that make it a suitable candidate for higher quality soil mix, including the potting mix.

Indeed, given the above, I did not found any source recommending peat humus for potting soil as a replacement of peat moss. Indeed, the most logical explanation is that peat moss has a winning mix of chemical and physical property. Moreover, given the higher cost and scarcity (I looked for it on Amazon USA and UK without success) of peat humus I do personally recommend peat moss for potting soil.

On the other hand, peat humus might be an interesting alternative for garden soil (for outdoor usage) as contributes to a heavier soil structure than peat moss, important for garden soil in raised beds for highly acidic loving plants (out of range for the most common edible herbs you might want to have home but suitable for other plants such as carnivore). Such application is indeed suggested by peat humus manufacturers.

Also, research on the subject highlighted (although not for indoor potting herbs) that peat humus might have a beneficial effect on plant growth  not for the nutrition (that is absent) but for its structure that seems boost growth as stated by the authors of the study

“Contaminated soil with HSE (humus material) after the 23 days vegetation experiment with rape demonstrated a significant increase of microbial substrate“.

Study

Is Peat Humus a Fertilizer?

Surprisingly, a few on the internet wonder if peat humus (or peat moss) is a fertilizer. The answer is no, peat humus is not a fertilizer. Indeed, in the case of peat humus, its nutritional content is so low that is almost totally “transparent” to the soil mix to which it is added. Indeed, peat humus has mainly a structural function that gives to the soil mix in which is in the capability to retain nutrients (not having), heat from the sunlight, and moisture.

Are Peat Humus and Humus The Same Thing?

The gardening world is not always crystal clear. Indeed, as you now know “peat moss” and “peat humus” are not the same despite the fact that they both have the word “peat” on it. The same applies to “peat humus” and “humus”. Those two mediums are different.

More precisely humus can be defined (I say “can” because no definition is universally accepted in the gardening world) as the portion of soil completely broken down (or decayed). Humus is an umbrella term for a variety of mediums. For instance, if you take compost material (that is partially decomposed, hence it is not humus) and you leave it to decay and broken down until there is no recognizable vegetable structure (fibers essentially) what is left can be called humus.

Hence, from the above, we can say that peat humus is a subcategory of peat humus. Indeed, as humus, peat humus presents a totally decayed organic base  that is mainly (although not entirely) given by peat moss, contrary to the “generic” humus that might be obtained by the total decay of other organic matter (like wood, leaves, insects etc…) without any contribution from Sphagnum moss. Moreover, humus can be developed in a way shorter time than peat humus.

Peat Moss and Peat Humus: An Open Environmental Concern

Both peat moss and peat humus come from peat bogs. This is the problem. Indeed, they are finite resources as a peat bog, to generate such material, require a long and ideal condition (without oxygen in particular water condition) long time window (hundreds of years) that, as you can guess, is way slower compared to the speed by which we, humans, extract it from the soil. Hence, its presence is not guaranteed in the long term.

Moreover, as a carbon sink (they capture carbon dioxide) it is quite dangerous to dig them out from the soil, considering also other beneficial actions that have on the area as discussed in this article Aspects For The Best Potting Soils and DIY Recipe. 

This is another reason, in case you are still wondering in using peat humus for your indoor herbs, to opt for more sustainable alternatives (like coconut coir and others).

Related Questions

Is peat humus acidic or alkaline? Peat humus, due to the decaying process, it is acidic.

Does peat moss have more nutrients than peat humus? Yes, peat moss has a slightly higher nutrient value, although still not enough for growing herbs as it needs to be integrated with fertilizer or compost material.

Can herbs grow on a peat-moss or peat humus only soil? No, at least in a healthy and stable manner. Indeed, the lack of nutrients (in both quality and quantity) is the majority issue that any plant might face in attempting growing in exclusively this medium.

Further Readings

The three soil types

Best potting soil

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