The Wild World of Moss

Timothy Newcomb, Anoka County Master Gardener

At night I sometimes find myself staring up at the stars, wondering what life is like on other planets.  But if you pay attention, you can find the most alien forms of life living right here on Earth, and sometimes in your own backyard.  For me, I recently discovered the wild world of moss and the alien forms that it comes in.

Moss is part of the Bryophyte family, which is a group of non-flowering, non-vascular plants.  They do not have true roots like other plants but instead have rhizoids that allow them to attach to their growing medium. They also do not produce seeds but instead reproduce via spores. Because they don’t have a vascular system like normal plants, water and nutrients are passed through the plant from cell to cell through osmosis.  This is part of what gives them their ability to absorb large amounts of liquid.  Some types of moss can collect as much as 20 times their weight in water.

 The life cycle of moss is very different from the life cycle of flowering plants we are most familiar with.  In flowering plants, a seed grows into the plant that will make flowers with stamen and pistils that will get fertilized to make seeds which then make more plants.

Moss, on the other hand, starts with a spore that creates a protonema which is a green mat-like structure that attaches itself to things like rocks, trees, or other suitable surfaces.  From the ends of these protonema the stems and leaves of moss grow and create the majority of the moss plant you see but stems and leaves are different from what you would expect on a normal plant. They are actually the reproductive parts of the moss.  These are differentiated between male and female, and you could almost think of these as the stamen and pistils of a flower, but that is the majority of moss plants.  When they are fertilized, they create zygotes or baby moss inside the female moss plant.  While attached to the mother plant it will grow and turn into a sporophyte that at maturity will release spores into the air to go and become moss elsewhere, starting the cycle over again.

This cycle has worked well for moss for over 470 million years and has allowed it to evolve into over 15,000 species globally.  Without true roots it can grow on almost any wet sturdy surface. This is one of the reasons that early moss and other bryophytes were some of the first plants to start gathering water and organic matter to areas so that later plants could develop.   Moss is a reservoir of water and nutrients, which is why we still use moss today as a growing medium for our more common plants. So, the next time you come across some moss, tip your gardening hat to it and thank it for making it possible for all the other plants we have today.