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The Germ Factor: Is Moss a Clean or Dirty Plant?

Moss is unlike any other plant. It grows close to the ground, likes to stay in the shade, and has a fuzzy, sometimes slimy feel to it. 

But does that mean moss is a dirty, germ and pest-ridden plant? Or is it some type of mold?

While moss does harbor some bacteria and microbes, it does not have any more toxins, germs, pests, or grime than any other plant. There are no species of moss that are poisonous to the touch. On the contrary, there are some species of moss that have been used for medicinal purposes.

To help dispel any fears that you might still have lingering, let me walk you through what moss is exactly and why moss is not especially attractive for germs, pests, and dirt.

What Is Moss?

First, let me quickly explain why moss is not a strange, green fungus or mold growing on the ground.

Moss falls under the kingdom Plantae and is a type of non-vascular plant, meaning it doesn’t have roots and xylem/phloem (plant “veins”) to transport water and nutrients. This would place it under a plant division called Bryophyta.

Moss isn’t some weird, fluffy mold. It’s a type of plant.

For more details about that, I explain more in my other article that you can check out here: Busting The Myth: Moss Is Not A Bacteria, Fungus, Or Algae

And just in case you were wondering, there are no known species of moss that are poisonous to the touch.

So back to the title of this article, why doesn’t moss have germs?

The short answer is moss is not the greatest host for germs, viruses, or pests.

Let me explain.

Why Is Moss Not Ideal For Germs And Bacteria?

Germs and bacteria prefer to grow on smooth, non-porous surfaces, especially in protein-rich environments. These would be places like toilet bowls, kitchen sinks, and bathtubs. 

The surface of moss does not have any of these characteristics which promote bacteria growth. Moss leaves are rough and porous due to their many stomata (think little breathing holes) used to control the rate of gas exchange.

Bacteria also tend to prefer warmer temperatures, which promotes growth and respiration.

Fortunately, moss prefers colder temperatures, even as low as -4 F (-20 C) and they can tolerate cold much better than they can tolerate heat. In fact, temperatures above 104 F (40 C) can be fatal for moss. 

Colder temperatures favored by moss will slow bacterial growth by slowing down nutrient uptake, enzyme activity, and metabolism.

Some species of moss even have their own antimicrobial compounds which further inhibit germ and bacterial growth, such as:

  • Lichen acids
  • Flavonoids
  • Terpenoids
  • Polyphenols
  • Essential Oils

So moss isn’t the most hospital environment for bacteria, but that doesn’t necessarily mean there’s absolutely no microbial life to be found on moss. 

Fortunately, the most common microbes are generally pretty harmless to humans:

  • Nematodes–ringworms not harmful to humans and prefer grubs
  • Mites–insects, some of which can cause itching if bitten
  • Tardigrades–water bears that pose no threat and do not spread disease
  • Rotifers–harmless microscopic animals
  • Gastrotrichs–hairy-bellied worms which are totally harmless to humans

Another fact about moss is that it tends to grow in areas with low foot traffic, where there’s often shelter, shade, and moisture. 

Low foot traffic means there are fewer opportunities for travelers to spread any germs and insects they might have picked up on their feet or wheels onto any moss they’re stepping on. It also means it should pick up less dirt and grime over time.

Speaking of insects…

Why Is Moss Not Ideal For Pests?

Moss grows low to the ground and does not provide much cover for pests to hide. Most pests would prefer to look elsewhere for other plants that can provide them with more shelter from predators

Moss can also grow in nutrient-poor soil conditions since they don’t uptake nutrients through a root system (they take it in directly through their leaves and stems). For example, you may see moss growing on top of a rock. 

These low-nutrient conditions may not provide sufficient nutrient sources for any pests to survive. It’s unlikely that the nutrients found in dew and rainwater will be enough for an insect, especially if they don’t have special adaptations to extract all the nutrients from the water.

To make themselves even more unappealing to unwanted guests, some species of moss also produce compounds that act as insect repellants such as:

  • Usnic Acid
  • Flavonoids
  • Essential oils

Overall, moss is a pretty clean plant and you don’t have to worry about potentially catching some disease from touching it.

Why Moss Is Beneficial For Health And Environment

Despite any rumors, misconceptions, or myths you may have heard, moss is a beneficial plant with many medicinal and environmental uses.

Historically, moss has been used as a medicinal herb for a variety of ailments. Here are some examples:

  • Letharia vulpina can be boiled and used to slow bleeding and reduce soreness from bruises, sores, and boils
  • Sphagnum moss has been used to sterilize wounds by lowering the pH levels around the wound during the first world war
  • Club moss is used in medicine as a diuretic to increase urine and to treat kidney and bladder disorders
  • Physcomitrella patens has been genetically engineered to produce therapeutic protein used in the human immune system

That list is just a little taste of how moss has been used. Even today, there’s a lot of research going on to discover new medicinal uses for mosses. If you do a quick search on google scholar, you can see research papers published as recently as 2023 (the year this article was written).

As for the environment, moss is known to serve multiple purposes:

So moss is absolutely not something to be avoided or afraid of. It’s actually very friendly and has a number of beneficial uses and plays a key role in our ecosystem.

Hope that makes moss a little more approachable for you!