Moss is a very simple type of plant that lacks conventional roots, stems, and leaves. The name refers to any species of the class Bryopsida and is part of the division Bryophyta. Bryophyta means the first green land plants to develop during the evolutionary process. It is thought to have evolved from very primitive vascular plants, and it has not given rise to any other plant life.
Lacking traditional vascular structures of true leaves, stems, and roots, moss growth is limited to moist locations. It is usually very hardy and grows almost everywhere, except under the sea. The plant usually grows vertically. Except for species in the commercially viable Sphagnum genus, it is generally of little use to humans or animals, although it is sometimes eaten in times of famine.
Moss is sometimes used to fill in barren habitats such as in dried lakes. It is also used to provide a backdrop for other plants in gardens, or simply to add color where grass refuses to grow.
Unrelated plants can share the name. These includes club moss; flowering moss; carageen, which is a type of algae sometimes used in health foods; reindeer moss, which is actually a lichen; and Spanish moss. Spanish moss is usually regarded as a parasite, since it often grows on other plants, such as oak trees. It grows in long streamers and is often seen in the Southern states of the US.
The Japanese have gardened with moss for centuries. Valued for its reduced need for watering, its greenness is considered to add a feeling of lushness and serenity to Japanese gardens.
This plant is often used in rock gardens or with water gardens, ferns, or ponds because it needs so little maintenance. With concerns about drought growing in different parts of America, it has become an increasingly desirable alternative to high-maintenance grass lawns and conventional gardens using shade plants.