Sphagnum moss has thick leaves and stems with an unusual structure that enable them to absorb up to 20 times their weight in water. There from 150 to 300 species of sphagnum mosses that grow together to form thick mats or bogs on the tops of ponds, lakes and swamps in northern areas of Europe and North America, Scandinavia and New Zealand. Their capability to hold water makes them useful as a medium in hydroponic growing systems and in potting mixes and soil amendments.
Sphagnum mosses do not have roots or vascular systems associated with higher plants; they do not produce flowers or seeds. Sphagnum moss absorbs moisture from the pond or swamp where it lives and from the air. Sphagnum leaves, ordinarily swollen with water, are shaped like cups or spears and are clear, green, reddish or yellowish; they produce nutrients through photosynthesis. The leaves and branches contains fine capillary tubes that store water. The spaces around these tubes hold air. The tubes and spaces around the leaves and branches combine to form a biological sponge.
Sphagnum moss spreads out over the surface of water, buoyed by the leaves and branching stems. Sphagnum on the top is exposed to the sun, necessary for photosynthesis. The moss below the surface of a sphagnum bog is unable to receive sunlight, so it dies. Living sphagnum moss combined with layers of dead sphagnum moss beneath the surface is called a bog. The layers of dead sphagnum moss grow thicker with time. The mattress-like layer of a sphagnum bog can cover acres of water. A sphagnum bog can grow thick enough support the weight of humans and animals as heavy as a moose; when it is walked on, it undulates.
Dry sphagnum capsules contain spores. The dry capsules burst, spreading the spores. Most reproduction, however, is done by the spread of sphagnum stems on the surface of the bog and by fragments of stems that grow into new plants.
Formation of Peat
The cold waters upon which sphagnum moss thrives are oxygen poor; the layers of dead sphagnum under the surface decay slowly. As these layers of dead sphagnum get deeper, they combine to form peat moss. Peat moss is an early stage of the formation of coal.
The capability of sphagnum moss to hold water makes it useful as a bedding to transport plants. It is also used to store and grow cuttings and bulbs and to line hanging baskets. It is used as bedding for worms, as a medium to grow plants hydroponically and to grow orchids. Sphagnum is grown and sold commercially for these purposes. Its capability to absorb made it useful as a surgical dressing in World War I.