How Does Moss Actually Grow? Its Growth Cycle Explained

Have you ever been deep in the forest and stumbled upon a stand of trees where their trunks and much of the ground were covered in moss? It’s amazing how much sound it absorbs, and it always gives the environment a truly ancient appearance.

And it’s fitting because moss is genuinely an ancient, primitive type of plant life – one that is very different from most of the plants you and I know. How different? For starters, it grows and reproduces entirely differently! But just how does moss actually grow?

Moss starts as a spore which, on a favorable surface and environment, will germinate and grow into a mat-like structure from which the recognizable parts of the plant, called gametophores, will grow. Once established, sexual reproduction starts over and the process will begin again.

Fascinating stuff! In some ways, moss reproduces more like fungi than typical plants, and it doesn’t even grow down into the soil to anchor itself.

Moss has very particular requirements for growth and survival, so as humble as you might think it is whenever you encounter it, it’s actually something kind of special.

At the very least, it can tell you more about the environment that you are in, so it’s worth learning! Keep reading and I’ll go into a lot more detail about the life cycle of moss below.

Moss Requires Ideal Conditions to Grow and Spread

Before we get to the actual reproductive and growth life cycle of moss, we need to know what kind of environment it will actually grow in. Turns out, most mosses have highly particular needs!

For starters, it will always need a damp, very damp environment in which to grow. Moss does not have typical roots like other plants, so it doesn’t draw water out of the soil.

It absorbs it directly through its foliage so anytime the air and its surroundings are dry, moss is suffering and then dying in short order.

Shade is another critical factor. Some mosses can tolerate a fair amount of sunlight, but partial shade, or even full shade, is best.

Intense sun can easily cook the tiny, delicate leaves of moss, and in any case will dry it out rapidly, exacerbating damage. Any shady areas that rarely get sun, or only indirect light, are prime locations for moss as long as they are moist.

Other than that, moss needs a stable surface on which to grow, and that can be nearly anything. Moss uses tiny adhesive structures called rhizoids to anchor itself, and it can grow horizontally, vertically, or even upside down.

Speaking of soil, moss prefers an acidic environment to grow in, and this is why it is so commonly found in areas with lots of dead leaves and other decaying plant matter.

Lastly, moss is surprisingly vulnerable to contamination. Air pollution can poison it, so you’ll rarely find it anywhere there have been chemicals spilled or harmful gases in the air.

Assuming we can check all of those boxes, we can be sure that moss will grow in time!

What Kinds of Surfaces Can Moss Grow On?

Moss can grow on nearly any surface as long as it has a slightly rough texture and is stable, meaning it will not shift.

Tree trunks, fallen logs and branches, stones and even man-made surfaces like brick, concrete, cinder block, shingles, tiles, and more can all host moss easily as long as the surroundings and atmospheric conditions are ideal.

The Lifecycle of Moss from Beginning to End

As mentioned, moss is recognizably plant life, but its reproductive life cycle is closer to that of a fungus than the plants you and I know.

The following is an abbreviated version that is mostly devoid of heavy-duty scientific terms so that anyone can understand it.

Spore Lands on a Surface

Even the largest carpet of moss growing across a tree trunk or a forest floor begins as an impossibly tiny single-celled spore. These spores contain the genetic information necessary for growth and all of the initial resources needed to begin that growth.

Moss spores, like fungal ones, are surprisingly durable and can remain dormant for a long time without being destroyed or disrupted until they land in ideal conditions or until conditions change wherever they happen to be.

Protonema Forms

Once a spore is in a shady, moist spot, it will germinate and spread, turning into what is called a protonema. The protonema, at first, looks like a thin, dusty fuzz or, at its thickest, like felt or gauze. This is the moss establishing itself and getting ready for further structural growth.

The protonema will spread and further anchor itself over time, but as long as conditions remain good and stable, it will soon begin to develop the structures that we can recognize as mature moss, structures called gametophores.

Growth into True Moss

The gametophores are the individual but multi-part structures that make up the moss itself as a mature plant. It’s basically a bunch of incredibly tiny, fine stems and individual leaves.

Except at very close range or even under magnification, it just looks like a soft, fuzzy carpet for most species. But if you can look at it up close, it would resemble miniature versions of ferns or other plants.

Sexual Reproduction

Once the moss has established itself and colonized an area, for lack of a better word, it will prepare to further reproduce and spread. This is accomplished through an intricate, and unique, type of sexual reproduction among plants.

Moss contains all of the structures needed to produce both male and female reproductive components, collectively referred to as gametes.

The male gametes must reach the female ones for fertilization by moving through water, and this is why a moisture-rich environment is, in part, so critical for moss to grow.

In dry times, even a single drop of dew can’t be enough to allow successful fertilization! Once fertilization is done, though, the moss develops a new structure called a sporophyte which contains a complete set of DNA.

New Spores Prepared

The sporophyte structure will produce a stalk that is, relatively speaking, taller than the other structures of the moss. At the top of this stalk is a capsule called a sporangium that will gestate and encode new spores with the fresh set of DNA.

Spores Expelled or Carried Away

Once the spores are produced and conditions are right, the sporangium capsule will open, either actively discharging the spores to be carried on air currents to new locations, or revealing them to be picked up accidentally by various bugs and other animals to be carried away.

Once those spores land, the process starts all over again at the top! Pretty cool, right?

Moss Can Also Reproduce by Transplantation

Note that moss can also reproduce via transplantation, either deliberately or incidentally.

If an intact section of moss is torn away from the parent gametophore mass and happens to land in another location that has equally suitable conditions, it will re-anchor itself and just keep growing!

Taking advantage of this tendency is how moss enthusiasts collect moss from the wild and bring it home for establishment in their own gardens or terrariums.

Does Moss Have Roots?

No, it does not but moss does have root-like structures called rhizoids. Although tiny and very difficult to see by themselves, these thread-like structures act like tendrils that collectively allow moss to latch onto whatever surface it has established itself on.

How Does Moss Get Energy to Grow?

Mosses make much of their food like other plants do, using photosynthesis. Mosses take up carbon dioxide from the air, water from the environment, and light through their foliage to produce glucose, a type of sugar that they then use for energy.

Note again that moss doesn’t have true roots, and so it does not absorb nutrients out of the soil using them.

Does It Always Grow on the North Side of Trees?

No, although this is an extremely persistent and common myth!

I won’t go into the whole thing here, but basically, the notion is that because the Sun orbits the equator of Earth, there will more often be shade on the north side of trees, and because moss craves shade, moss will only grow on that side…

Sadly, this isn’t true, and relying on it out in the wild will get you very lost. It’s also worth pointing out that the myth wouldn’t apply to the southern hemisphere because the sun would be constantly shining on the north side of those trees; in that case, moss would only grow on the south side of trees!