5 environmental benefits of moss gardening

5 environmental benefits of moss gardening

by Timber Press on September 9, 2015

in Gardening, Popular

A green roof at the North Carolina Arboretum demonstrates mosses are a viable alternative to sedums and grasses. Image: Annie Martin

The Magical World of Moss Gardening author Annie Martin makes the case for going green with mosses.

We are bombarded with television commercials on how to go green in our gardens—but most of the time, environmentally unfriendly methods are recommended to achieve green, particularly the application of chemicals to promote growth, inhibit plant diseases, and eliminate insect pests. By contrast, moss gardening is truly green through and through. You do not need a chemical “green thumb” to succeed—no fertilizers, pesticides, or herbicides. By eliminating the use of poisons, you can play a valuable role in reducing groundwater contamination and runoff of hazardous chemicals into our natural water resources. When you stop mowing, you are taking personal steps to reduce air pollution. Mosses are an environmentally benign way to conserve water, control erosion, filter rainwater, clean up hazardous chemicals, and sequester carbon. Also, mosses serve a valuable ecological role as bioindicators for air pollution, acid rain, water pollution, and wastewater treatment.

All of these side benefits of beautiful bryophytes make them good eco-friendly choices for our gardens. Add the feathers of a responsible steward and champion for sustainable landscapes to your jaunty moss gardener’s hat. Every little bit helps, and it all adds up to a better world.

In places where nothing else will grow, mosses provide an outstanding yearround green solution. Leucobryum glaucum and Dicranum scoparium skirt this tree base. Image: Annie Martin

1. No poisons or pollution
Many gardeners and landscapers rely on fertilizers, but as a moss gardener, you will need no soil supplements to encourage growth. In fact, too much nitrogen along with other macro, secondary, and trace nutrients could be harmful. Since mosses “eat” dust particles in such minute quantities, fertilizers could actually hamper moss growth. Even organic fertilizers might provide too much of a particular nutrient or micronutrient.

Beneficial insects, salamanders, frogs, and the like live in moss colonies. Because of internal anti-herbivory compounds, mosses taste bad to typical garden insect pests or critters. Deer might stomp around, but they don’t eat mosses. Reindeer have been documented eating reindeer moss, but it is a lichen and not a true moss (bryophyte). Further, insects inhabiting mosses do not eat them or cause any significant damage. Therefore, pesticides are unnecessary.

To complete your shunning of the trio of harmful environmental substances, you can stop using any herbicides, too. Biochemical compounds in mosses function like antibiotics to deter any diseases, so mosses are not subject to the vast array of problematic diseases that plague other land plants. It is a rare occasion when mosses get any fungal disease or harmful pathogens. Although it is possible for mosses to get sick, in my experience it been the exception rather than the rule. When mold occurs, it is usually due to overwatering, lack of attention to debris, or multilayering of moss colonies as a result of critter shenanigans. As moss gardeners, we do need to be aware of problems and troubleshooting protocols. Information is becoming available in this area as scientists are beginning to research potential fungal issues regarding cultivated moss growth.

By planting mosses instead of a grass lawn, you can help reduce air pollution. Not all air pollution comes from industrial sites or big cities. Each week, millions of suburban grass lovers send carbon smoke signals into our atmosphere. If you are still cutting your grass with a gasoline-powered mower, you are contributing to this problem. Lawnmowers, weed eaters, and leaf blowers are only minimally regulated. They do not have catalytic converters, and that obnoxious smell is a harmful discharge. Mosses do not have to be mowed.

Mosses don’t need to be mowed, thus avoiding the air pollution produced by mowers, and Sphagnum mosses actually clean our air. Image: Annette Launer

2. Water conservation
Because of low annual rainfall in arid regions, water supplies can be precious commodities. Watering restrictions are the norm. During times of drought, some places may temporarily restrict watering for landscape purposes. Mosses do require moisture and thus are not xeriscaping solutions for landscapes; they do much better if watered regularly. But if you are concerned about water conservation, using rainwater collection systems and these tiny plants that require only brief, light watering sessions could be part of your solution. Rather than long drenching soaks weekly, mosses prefer short sessions each day. Misting irrigation systems that use a fraction of the water of other kinds of irrigation systems are enough to keep mosses happy.

3. Erosion control and flood mitigation
Many moss species are guardians of the soil and keep it from washing away. Polytrichum commune, an upright grower, can be planted on steep hillsides in nutrient-poor soil. This species is an excellent solution to erosion concerns even in sunny locations. Its long rhizoids steadfastly hold red clay, gravel, and sandy substrates in position. Steep, almost totally vertical slopes hold together as tiny Pogonatum mosses cling to exposed substrates. Rushing water slows down to enter the groundwater table gradually thanks to the absorptive properties of moss leaves.

The harsh appearance of riprap used to hold a bank in place can be softened by introducing Thuidium delicatulum, a fernlike sideways grower. Planting mosses in drainage ditches reduces the impact of stormwater runoff. And let’s not forget our roofs—bryophytes can be featured in contemporary green roofs that insulate and cool, filter air pollutants, and reduce stormwater runoff.

In America, most newly constructed green roofs are composed of sedums or grasses, but mosses are used as part of green roofs in European countries, and in 2011 I created a roof at the North Carolina Arboretum as an example of how mosses are feasible on green roofs. Incorporating rainwater harvesting with a misting irrigation system, this green roof makes it possible for the mosses to do well even in direct sun. Polytrichum and Ceratodon species have been the best performers, with intense growth and several seasons of sporophytic displays, but I must acknowledge that Leucobryum species have struggled, so not all mosses are happy campers on rooftops. Mosses such as Bryum argenteum, Ceratodon purpureus, and Hedwigia ciliata do tolerate high heat and grow on many roofs in my region. In the Northwest, Dicranoweisia cirrata, Bryum capillare, Rhytidiopsis robusta, Racomitrium canescens, and Tortula princeps are abundant on roofs.

Thuidium delicatulum covering a steep bank in the Vickery garden in Brevard, North Carolina, provides effective erosion control. Image: Annette Launer

4. Filtration and phytoremediation
In terms of water filtration, Sphagnum species are especially effective as filtering and absorbing agents in the treatment of wastewater. Research indicates that mosses can be useful in addressing toxic discharge of undesirable elements (silver, copper, cadmium, mercury, iron, antimony, and lead). In urban areas, these advantages could play an important role in dealing with excessive rainfall, poor drainage, and flash flooding associated with nonpermeable surfaces. Further, mosses filter out organic substances such as oils, detergents, dyes, and microorganisms. In our streams and rivers, bryophytes are essential in food web interactions and nutrient cycling, contributing to the total stream metabolism.

Mosses can help reclaim land at abandoned sites where mining has occurred. Many species are tolerant of heavy metal toxins. Scopelophila cataractae, commonly referred to as copper moss, is often associated with copper deposits and can be the first species of plants to reappear without any special efforts, yet the beneficial effects of this category of pioneer plants may go unnoticed in formal efforts to restore forsaken landscapes.

In places where people brave extreme winter weather, salt is used extensively by road maintenance crews and homeowners digging out. As the snow melts, these salts are absorbed into the soil and penetrate into groundwater. Additionally, after a heavy storm, runoff water from nonpermeable surfaces rushes through urban drainage systems to lakes, rivers, wetlands, and coastal waters. According to the United States Geological Survey, “Stormwater picks up potential pollutants that may include sediment, nutrients (from lawn fertilizers), bacteria (from animal and human waste), pesticides (from lawn and garden chemicals), metals (from rooftops and roadways), and petroleum by-products (from leaking vehicles).” I am glad to report that mosses are part of the solution rather than being victims of pollution—they slow down stormwater while tolerating unfiltered contaminants. Sometimes I rescue mosses from places subject to runoff from roads and impervious asphalt parking lots. Despite exposure to oil residue from cars and trucks as well as seasonal road salt, bryophytes survive and even thrive.

Furthermore, mosses sneak in and grow at plant nurseries in spite of sanitation practices that include chlorination, bromine injections, and/or ozonation of irrigation water. Wouldn’t you want plants that can handle even the worst of circumstances in your own yard?

This serene green retreat was once a driveway. Image: Annie Martin

5. Carbon sequestration
Mosses play a significant environmental role in the global carbon cycle as the largest land repository for carbon on the planet. Sphagnum peatlands soak up vast amounts of carbon dioxide from the air, far exceeding the rate of carbon sequestration by all rainforests combined. (When the rate of plant production in an ecosystem exceeds the rate of plant decomposition, carbon sequestration occurs.) Peatlands contain as much carbon as is present in Earth’s entire atmosphere; it is estimated that they sequester between 198 and 502 billion tons of carbon.

You see, more than 60 percent of the world’s wetlands are composed of Sphagnum mosses and decaying vascular plant matter, and Sphagnum-based bogs cover 2 to 3 percent of our planet’s land mass—more total land mass than all the rest of the plants on Earth, including all other trees, grasses, and flowers, combined. Sphagnum may sequester more carbon than any other land plant, according to bryophyte ecologist Janice Glime, although aquatic algae do exceed Sphagnum in volume of carbon sequestered globally.

These globally significant ecosystems contain one third of the world’s soil carbon and 10 percent of our freshwater resources. Approximately 175 countries around the world have peatlands that serve as carbon sinks. In North America, large expanses of Sphagnum peat occur from the boreal forests of Canada to the Everglade’s fens and swamps in Florida.

While Planet Earth’s inhabitants could benefit from these moss enclaves, regrettably we are destroying them. The extensive devastation of peat bogs is happening due to a variety of factors including global warming, irresponsible harvesting in mass quantities, agricultural expansion, commercial exploitation, and fire. It is estimated that 7 percent of peatlands globally have been exploited by clearing and draining areas for agricultural endeavors. Indonesia has more tropical peatlands than any other nation but is losing them at an alarming rate—nearly 250,000 acres each year.

The loss of rainforests through massive clear-cutting is associated with degradation of air quality and loss of carbon sequestration capacity worldwide, and the loss of Sphagnum biomass may have a similarly negative impact on global air quality and climate change. Billions of tons of methane, a greenhouse gas more potent than carbon dioxide, are being released as the world’s largest peat bog (in Siberia), equal to the size of France and Germany combined, is thawing for the first time in eleven thousand years. And when peat bogs catch on fire, they can smolder for weeks, months, or years, releasing carbon dioxide all the while. The ominous cloud that covered Southeast Asia in 1997, attributed to Indonesia’s burning wetlands, lasted for months.

The destruction and corresponding decline of peat bogs due to humans could be turned around with the application of best management practices to regrow mosses. Researchers at Bangor University in Wales are currently investigating how the growth rate might be increased to achieve sustainability.

Walking on mosses is encouraged in the Kenilworth moss garden in Asheville, North Carolina, which features more than a mile of mossy trails. Image: Annie Martin

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