Marvelous Mosses

Mosses. We’ve all seen them — those low-growing, often cushiony-looking plants that may carpet a forest floor, grow on the bark of trees, or cover a rock wall. It’s easy to traipse past them on a trail and see only a blur of green. But stop for a moment to truly look at them, and you might be surprised. 

“When Linda gave me the hand lens and I saw the mosses through that, I couldn’t believe it! It was like a whole new world opened up,” my friend told me, her voice brimming with enthusiasm. Up close, she said, mosses are full of intricate details. 

A few months later, we set out to look at mosses at Wild Haven Nature Area in Columbia. The roughly 100-acre area is owned and cared for by the Columbia Audubon Society. Louise Flenner, a member of the Audubon chapter, has written a guide that directs people to 10 moss species along a portion of the area’s trails. We found the guide online. Armed with a printout, we stepped onto the path.

A Brief Foray into Moss Biology

Mosses don’t function like the plants we normally think of (for example, a daisy or a maple tree). Knowing this can help you better understand what you’re looking at when you examine them. Mosses have no veins or true roots, and they reproduce with spores instead of seeds. They hold onto soil, rocks, or logs with tiny rootlike structures called rhizoids. Lacking an advanced vascular system for transporting water and nutrients, mosses absorb moisture and nourishment from the air and rainfall. Their leaves are usually only one cell thick, which makes it easier for water to disperse throughout the plant. Because they are small and can’t pull water from deep in the ground, many species are prone to drying out and thrive in wet and humid places. 

The spores of mosses form inside a small capsule that often is on the end of a thin stalk that grows out of the main green part of the plant. These spore-bearing structures may not be present year-round, but they can be helpful for telling mosses apart as well as for telling mosses from liverworts and hornworts — two other plant types that are also small, nonvascular, and reproduce with spores. (See sidebars for information on plants that can be confused with mosses and for more on moss spores and reproduction.)

Moss Types

About 12,000 moss species are found across the world. More than 300 species live in Missouri. Biologists group them into four main categories based on how they grow. In Missouri, most mosses fall into two groups: cushion mosses, which grow in rounded mounds or clumps, and carpet mosses, which spread and branch out, forming mats across a rock or other surface they’re growing on. Sphagnum mosses (or peat moss) is a third type. They have a shaggy appearance, often grow densely in bogs, and are more common in northern climates. Missouri has 18 species of peat moss. Dendritic (or tree) mosses are the fourth type. They look like a mat of tiny trees. Our state only has two species of these. 

On the self-guided moss trail, we encountered only carpet and cushion mosses. The first belonged to the carpet group. Named delicate fern moss, its leaves look like miniature ferns, dozens of tiny, connected ferns that grow horizontally, branching and spreading across the ground like a carpet. 

It was here we discovered that we’d forgotten to bring a hand lens, which is the equivalent of forgetting your binoculars when you go birdwatching. But, as with birdwatching, you can still enjoy seeing the birds (mosses); you just can’t see all the defining details.

The moss trail guide, however, provides the species names and photos, so we just needed to follow the trail directions and match the photos and descriptions in the guide to the mosses featured at each location. A hand lens would have shown us more, but we were still able to see how each species was unique. We even found two that were not in the guide, which made 12 species, all in just under a mile. 

What’s in a Name?

At first, taking time to identify mosses felt a bit eccentric, like something only hardcore botanists would do. But Julie Schroeder, an amateur naturalist from central Missouri, has a different perspective.

 “Imagine if you couldn’t tell the difference between a cardinal and a bluebird — if you just saw them as ‘birds,’” Schroeder says. “Or if you couldn’t tell the difference between a daisy and a poppy — it’s just a ‘flower.’ That’s how most people are with mosses, lichens, and liverworts.” 

Lorie Hetrick-Volenberg, author of the forthcoming book Mosses of Missouri Through a Hand Lens, takes the view that “we have a closer association with things if we can put a name to them.”

Her interest in identifying mosses happened “by accident.” She was researching lichens and learning to look at them under a microscope. Remembering from botany class that most mosses are just one cell thick, she grabbed some from her yard as practice material for using the scope. That’s when, she says, she began to realize how varied mosses are and that it’s “not necessarily easy to figure out what [species] they are. And I was just hooked by the challenge of it. But then I was also hooked by being so amazed again of the diversity of what is out there. And I just wanted to learn more and more about them.” 

Speaking for myself, I can feel accomplished just figuring out what family or genus a moss belongs to. Is it a fern moss, thyme moss, goblet moss, broom moss, beard moss, tree moss, or something else? But mosses do have some rather spectacular species names. Consider yellow yarn moss, tangled thread moss, bonfire moss, baby tooth moss, slender starburst moss, oil spill moss, and my favorite, tiny tornado moss.

Yet, intriguing names are only one facet of what’s fascinating about mosses. 

Ecologically Mighty 

Retired biologist and former MDC Naturalist Bonnie Anderson says what impresses her most about mosses is their “ancient history” and “their importance to the existence of everything,” referring to how mosses were one of the first plants to develop. Evolving about 450 million years ago, before flowering plants, they helped fill the atmosphere with oxygen, setting the stage for other organisms. Mosses also were one of the first plants to colonize land, growing on rock surfaces, breaking down the rock, and beginning the process of soil formation. 

Since those early times, mosses have continued to make contributions. 

“The research that is starting to come out as far as our understanding about the roles that they play is stellar,” says Hetrick-Volenberg. 

Mosses, she points out, not only produce soil, but they also protect and regenerate soil. If soil is exposed, “it’s not uncommon to see mosses within a year or two come in to start to cover that land, and as the soil heals and regenerates, other plants come in.” 

Some seeds even sprout inside of mosses and then send roots into the soil. Because mosses absorb nutrients from the air, when they die and decompose, they pass those nutrients into the soil for other plants to use. Studies have also found that soils with mosses have fewer plant pathogens than soils without moss. So, mosses are good for neighboring plants.

And, Hetrick-Volenberg says, “they play a huge role in sequestering carbon and nitrogen, and that’s a big one as we all know with climate change going on.”

Many moss species pull pollutants from the air, acting as purifiers, but they also “are like the canary in the coal mine,” Anderson says. “They are indicator species that let us know if things are going well or if they’re not going well.” 

By testing mosses growing on trees in Portland, Oregon, researchers found areas with high levels of cadmium in the air, a heavy metal with links to cancer and kidney disease. This and other studies show that some moss species could be used as a tool for gauging air pollution. 

At the local level, patches of moss provide microhabitats for tiny animals such as snails, sowbugs, centipedes, and other invertebrates, which in turn make these patches excellent hunting grounds for shrews, frogs, and other insect eaters. Mosses also are a popular material for nests. Birds, mammals, and even bumblebees gather them. The moss may be woven into the nest or used as cushioning and helps insulate against the cold. 

Mosses themselves handle the cold well. Many have antifreeze properties and stay green all winter. 

“Mosses are extremely resilient to environmental conditions,” says Missouri State Botanist Malissa Briggler. “They can go through dry periods where the plants completely dry up and are instantly restored once moisture returns.” 

You can watch this transformation happen. On our moss walk, we poured water on part of a tree apron moss, and within seconds, the moss began changing from brownish to bright green and the leaves unfurled as they took in the moisture. 

Although mosses can be found throughout Missouri, “MDC currently tracks populations of 121 moss species that are considered rare and of conservation concern,” Briggler says. “Some species are specific to unique microhabitats that stay cool and moist even during the heat of summer.” 

Whether rare or common, all our mosses are part of our state’s remarkable natural heritage. 

“They are resilient,” says Hetrick-Volenberg. “They’re hardy. They’re quite amazing at what they can do and the fact that they’ve been here for so long ... They’re just really cool for being such a little tiny thing.” ▲

Dianne Van Dien is an editor for MDC and writes Nature Lab for the Missouri Conservationist. She enjoys learning about the small things in nature that often go unnoticed.