Sphagnum

Sphagnum
Sphagnum flexuosum
Scientific classification
Kingdom:	Plantae
Division:	Bryophyta
Class:	Sphagnopsida
Subclass:	Sphagnidae
Order:	Sphagnales
Family:	Sphagnaceae
Genus:	Sphagnum L.
Species
Sphagnum affine Sphagnum angustifolium Sphagnum girgensohnii Sphagnum magellanicum Sphagnum novo-caledoniae Sphagnum russowii for more species see text.

Sphagnum is a genus of between 151 and 350 species of mosses commonly called peat moss, due to its prevalence in peat bogs and mires. A distinction is made between sphagnum moss, the live moss growing on top of a peat bog on one hand, and sphagnum peat moss (North American usage) or sphagnum peat (British usage) on the other, the latter being the decaying matter underneath.^[1] Bogs are dependent on precipitation as their main source of nutrients, thus making them a favourable habitat for sphagnum as it can retain water and air quite well. Members of this genus can hold large quantities of water inside their cells; some species can hold up to 20 times their dry weight in water, which is why peat moss is commonly sold as a soil conditioner. The empty cells help retain water in drier conditions. In wetter conditions, the spaces contain air and help the moss float for photosynthetic purposes. Sphagnum and the peat formed from it do not decay readily because of the phenolic compounds embedded in the moss's cell walls. An additional reason is that the bogs in which Sphagnum grows are submerged, deoxygenated, and favor slower anaerobic decay rather than aerobic microbial action. Peat moss can also acidify its surroundings by taking up cations such as calcium and magnesium and releasing hydrogen ions.

Common Sundew in a Sphagnum moss cushion

Individual peat moss plants consist of a main stem, with tightly arranged clusters of branch fascicles usually consisting of two or three spreading branches and two to four hanging branches. The top of the plant, or capitulum, has compact clusters of young branches. Along the stem are scattered leaves of various shape, named stem leaves; the shape varies according to species. The leaves consist of two kinds of cell; small, green, living cells (chlorophyllose cells), and large, clear, structural, dead cells (hyaline cells). The latter have the large water-holding capacity.

Sphagnum species have a dominant sporophyte and spores are released from specialized black, shiny capsules located at the tips of thin stalks. They also reproduce by fragmentation.

Peat moss can be distinguished from other moss species by its unique branch clusters. The plant and stem color, the shape of the branch and stem leaves, and the shape of the green cells are all characteristics used to identify peat moss to species.

Geographic distribution

Peat mosses occur mainly in the Northern Hemisphere where different species dominate the top layer of peat bogs and moist tundra areas. The northernmost populations of peat moss lie in the archipelago of Svalbard, Arctic Norway at 81° N.

In the Southern Hemisphere, the largest peat moss areas are in New Zealand, Tasmania, southernmost Chile and Argentina, but contain comparatively few species. Many species are reported from mountainous, subtropical Brazil, but uncertainty exists regarding the specific status of many of them.

Spore dispersal

As do many other mosses, Sphagnum disperses its spores through the wind. But the tops of spore capsules are only about 1 cm above ground, and the wind is too weak that low. So the spores are discharged by air that is compressed as the spore capsule dries. Thanks to vortex rings created during the discharge, the spores reach a heigh of 10 to 20 cm. The acceleration of the spores is about 36,000 times g, the acceleration of gravity.^[2][3]

Uses

Peat moss soil amendment, made of decayed, compacted Sphagnum moss

Decayed, compacted Sphagnum moss has the name of peat or peat moss. This is used as a soil conditioner which increases the soil's capacity to hold water and nutrients by increasing capillary forces and cation exchange capacity (CEC). This is often necessary when dealing with very sandy soil, or plants that need an increased moisture content to flourish. One such group of plants are the carnivorous plants, often found in wetlands (bogs for example). Dried Sphagnum moss is also used in northern Arctic regions as an insulating material. Peat moss is also a critical element for growing mushrooms; mycelium grows in compost with a layer of peat moss on top, through which the mushrooms come out, a process called pinning.

Anaerobic acidic Sphagnum bogs are known to preserve mammalian bodies extremely well for millennia. Examples of these preserved specimens are Tollund Man, Haraldskær Woman, Clonycavan Man and Lindow Man. Such Sphagnum bogs can also preserve human hair and clothing, one of the most noteworthy examples being Egtved Girl, Denmark. Because of the acidity of peat, however, bones are dissolved rather than preserved. These bogs have also been used to preserve food. Bog butters have been found in Scottish and Irish peat bogs.^[4] Containing butter or lard, bog butters have been found that are up to 2000 years old.^[5]

Sphagnum moss has also been used for centuries as a dressing for wounds, including during both World Wars. It is absorptive and extremely acidic, inhibiting the growth of bacteria and fungi. However, see Health Dangers below.

Sphagnum moss is used as an environmentally-friendly alternative to chlorine in swimming pool sanitation.^[6] The moss inhibits the growth of microbes and reduces or eliminates the need for chlorine in swimming pools.^[7]

Peat moss is used to dispose of the clarified liquid output (effluent) from septic tanks in areas that lack the proper soil to support an ordinary disposal means or for soils that were ruined by previous improper maintenance of existing systems.

In New Zealand, both the species S. cristatum and S. subnitens are harvested by hand and exported worldwide for use as hanging basket liners, as a growing medium for young orchids, and mixed in with other potting mixes to enhance their moisture retaining value.

It is also used at horse stables as a bedding in horse stalls. It is not a very common bedding, but some farm owners choose peat moss to compost with horse manure.

It can also be used as a substrate for tarantulas as it is easy to burrow into and contains no insecticides which could kill the spider.

There is a difference in naming conventions for similar things related to sphagnum moss. The terms that people use when referring to moss peat, peat moss, and bog moss can be taken out of context and be used when reference is actually being made about a plant that is still growing, as opposed to the decayed and compressed plant material. These terms are commonly used for both forms of the same plant material, resulting in confusion as to what the speaker is actually talking about.

Conservation

Mer Bleue Conservation Area, a large protected Sphagnum bog near Ottawa, Ontario, Canada.

Large-scale peat harvesting is not sustainable. It takes thousands of years to form the peat "bricks" that are harvested in just a week. In particular, the extraction of large quantities of moss is a threat to raised bogs. Coir has been touted as a sustainable alternative to peat moss in growing media.^[8] Another peat moss alternative is manufactured in California from sustainably harvested redwood fiber and sold under the brand name LignaPeat.^[9]

During the 17th century in the Dutch Republic, peat bogs were drained to feed a burgeoning peat mining industry. The system of dikes and waterways existing today in the Netherlands was once a peat bog.^[10]

More than 90% of the bogs in England have been damaged or destroyed.^[11][12] A handful of bogs have been preserved through government buyouts of peat-mining interests.^[13]

New Zealand

Care is taken during the harvesting of Sphagnum moss in New Zealand to ensure that there is enough moss remaining to allow regrowth. This is commonly done using a 3 year cycle. If a good percentage of moss is not left for regrowth, the time that it takes for the swamp to revert to its original state can be up to a decade or more if serious damage has occurred.

This "farming" as done in New Zealand is based on a sustainable management program approved by New Zealand's Department of Conservation. This plan ensures the regeneration of the moss, while protecting the wildlife and the environment. Most harvesting in New Zealand swamps is done only using pitchforks without the use of heavy machinery. During transportation, helicopters are commonly employed to transfer the newly harvested moss from the swamp to the nearest road. This is an important component of the transportation process, as it prevents damage to other components of the ecosystem during the initial transportation phase. The removal of sphagnum moss in a managed environment does not cause a swamp to dry out. In fact the swamp environment is improved such that the regrown moss is normally better quality than the previously harvested moss that was removed.

The greatest threat to the existence of sphagnum moss swamps is the intentional draining for encroaching farmland.

Health dangers

Many of warnings issued on the Internet and other publications concerning the dangers of using and handling sphagnum moss have to be considered and taken seriously. Since sphagnum moss useful properties that can be used for bonsai cultivation and is widely used by enthusiasts, how seriously should the above warning be taken? These are some exemple: "……….Sphagnum moss can be a source of a chronic fungal disease called sporotrichosis, which enters the skin through scratches and abrasions. From there it can get into your lymph nodes and cause swelling of the joints. The entry point will develop blisters. If treatment is not given, amputation of the infected area can become necessary; death from the disease can also occur……………." Sporotrichosis is a fungal infection that usually affects the skin. It is mainly an occupational disease of farmers, gardeners, and horticulturists. Though the fungus that carries sporotrichosis is found in sphagnum moss, it should be noted that it also occurs and can be transmitted into cuts in human skin via soil, hay, barbed wire, pine needles, thorns (particularly those of the Rose family such as Rose species and Hawthorn) and other plant materials. It has also been found growing on plant debris in soil and on the bark of trees and shrubs, (wild and cultivated). The threat of Sporotrichosis is certainly not limited to just Sphagnum Moss.

It should also be understood that not all Sphagnum moss carries Sporotrichosis. According to reports by the Wisconsin Division of Health, Bureau of Community Health and Prevention (BCHP), in 1981 a diagnosis of sporotrichosis was found in two brothers employed at a garden centre in Wisconsin. An investigation of the garden centre by the BCHP revealed two additional cases of sporotrichosis among the employees. The garden centre had sixteen workers make funeral wreaths during the Winter of 1980. The sphagnum moss used was harvested from bogs located in central Wisconsin and was purchased from one wholesale dealer. Of seven male workers regularly involved in making the wreaths, four developed sporotrichosis. However, in an investigation of a local cemetery where 12 employees produced 2,000-3,000 wreaths per autumn using sphagnum moss purchased from the same Wisconsin supplier, no additional cases were noted. It appeared that the source of the outbreak was limited to just one bad batch of Sphagnum from a wholesale dealer who had also supplied countless quantities of Sphagnum free of Sporotrichosis. It would appear that in the majority of cases such as this one, Sphagnum carry the fungus causing Sporotrichosis is the exception rather than the rule. Most Sporotrichosis infections are limited to the skin. Cases of joint, lung, and central nervous system infection have occurred but are very rare.

The first symptom of Sporotrichosis is usually a small painless bump that looks like an insect bite. It can be red, pink, or purple. The bump usually appears on the finger, hand, or arm where the fungus first entered through a break in the skin. This is followed by one or more additional bumps that open, might look like boils, and are very slow to heal. The first skin bump can appear any time from 1 to 12 weeks after exposure to the fungus, but usually within 3 weeks. Until recently, sporotrichosis was treated with potassium iodide, however a new drug Sporanox is now used for treatment because it causes fewer side effects than potassium iodide. Treatment can often take several weeks until the skin sores are completely healed. Bear in mind that the risk of Sporotrichosis is very small; in the US the incidence of infection is not precisely known but is estimated at only 1-2 cases per million people. An estimated 200-250 cases occur per year.

Statistically speaking, it is more dangerous to cross the road. I handle soil, trees, sphagnum moss on a daily basis and have done for a number of years without incident as have many other enthusiasts, nurserymen and gardeners, however I am duty bound to advise that where possible, wear gloves and long sleeves when handling wires, rose bushes, hay bales, pine seedlings, or other materials that can prick the skin on a continual or daily basis. If you have broken areas of skin, avoid prolonged direct contact with soils, sphagnum moss and similar materials.

Species

• List of Sphagnum species

Footnotes

References

Eddy, A. (1988). A Handbook of Malesian Mosses. Volume 1. Sphagnales to Dicranales. UK: British Museum (Natural History). pp. 202 pp. ISBN 0565010387. 

External links

• Sphagnum Moss vs Sphagnum Peat Moss at Virginia Co-Op Extension