The Science Of Bryum Moss | Habitat, Distribution, Characteristics & More

Bryum Moss, also called ‘Sun Moss‘, is scientifically described as ‘Bryum caespiticium’. This moss is one of the most popular choices by landscapers and gardeners because of its ability to survive in areas with moderate to full sunlight. Below we will discuss name and synonyms, the taxonomy, habitat, distribution, characteristics, its internal structure, and how it reproduces.

1. Scientific Name

The scientific name for Bryum moss is ‘Bryum caespiticium‘. This moss species belongs to the Bryaceae family, which contains over 1000 species and is one of the most diverse and widespread moss families. One relative is Bryum argenteum, the sidewalk moss. The two are easily confused, and it is caespiticium, not argenteum, that we supply as Sun Moss.

2. Synonyms

Bryum moss is not the only common name for Bryum caespiticium. It is also known by other synonyms such as;

• Sun Moss;
• Dry Calcareous Bryum Moss;
• Silver Green Bryum Moss, which here means caespiticium and not the separate species Bryum argenteum; and
• Tufted Thread-Moss.

3. Taxonomy

The taxonomic classification of Bryum caespiticium is as follows:

• Kingdom: Plantae
• Division: Bryophyta
• Class: Bryopsida
• Order: Bryales
• Family: Bryaceae
• Genus: Bryum
• Species: Bryum caespiticium

Tip: Bryum is sold as Sun Moss, by the square foot for paver joints and open ground, or as terrarium grade clumps for indoor builds.

4. Habitat

Bryum moss can be found on sidewalks and walls in urban areas, woodlands, gardens, and grasslands. This moss species has a very adaptable nature allowing it to grow in various substrates such as soil, rocks, and even brickwork, and is appreciated for its resilience to sunlight.

4.1 Urban Areas & Gardens

In cities, this moss often colonizes the cracks of sidewalks and walls because it can tolerate pollution and occasional trampling showing how resilient this species is. It is also a popular choice for sunny moss gardens and it has been widely adopted by landscapers and moss enthusiasts.

4.2 Woodlands

In woodlands, Bryum moss grows on the ground and can form dense mats which can provide a habitat but also food for small wildlife. In woodland it takes the moister, shadier ground like most mosses, but unlike most mosses it does not need it. Bryum is one of only two species we supply that hold in open sun all day, the other being Full Sun Moss, Racomitrium canescens, and it tolerates dry spells that would flatten a shade moss.

4.3 Grasslands

You can also find this moss in grasslands where it grows among grasses and other low vegetation and is often a sign of a healthy ecosystem.

5. Distribution

Bryum moss has a wide distribution and you find it all around the globe (cosmopolitan distribution), including North America, Europe, Asia, and Australia. This moss species is well adapted to different climates and environmental conditions.

From the temperate regions of North America and Europe to the tropical forests of South America and Asia, Bryum Moss has established itself as a common species. It grows in natural and urban environments alike, and its tolerance of pollution, heat and trampling is why it turns up in places no other moss will.

The key factors contributing to the success of Bryum Moss are caused by;

• its high tolerance for different moisture levels,
• its ability to grow in a variety of substrates;
• its ability to withstand periods of drought and more sunlight than most mosses;
• and it can adapt to, and cope with environmental disturbances.

6. Physical Characteristics

You can recognize Bryum Moss by its small, green, and cushion-like tufts. The leaves are normally bright green and can have a glossy appearance. The stems of this moss species are short, which creates the cushion-like appearance.

6.1 Color

This moss stands out with its bright green to yellowish-green, small, cushion-like tufts. The leaves of this moss are ovate to lanceolate and they have a distinctive midrib extending to the leaf tip.

6.2 Size and Structure

The stems of Bryum caespiticium can grow up to 2-3 cm tall and it has small leaves of about 2-4 mm in length. Like most other mosses, it can form dense, mat-like growth which contributes to its ecological role in covering and stabilizing soil.

6.3 Capsules and Sporophytes

A very distinguishing feature is its sporophytes. They are borne on long stalks (setae) and capped with elongated, pear-shaped capsules. These capsules are reddish-brown (if the moisture levels are favorable) with spores for reproduction.

7. Reproduction

Bryum moss can reproduce in two ways, namely asexually and sexually. It can form spores in the capsules and they can be carried off by wind or water for germination. Asexual reproduction happens through fragmentation.

7.1 Sexual Reproduction

During the reproductive season, the male and female gametangia (antheridia and archegonia) develop on separate moss plants. After a plant is fertilized, it develops a sporophyte and this eventually produces the spores that will be carried by the wind or water to germinate another plant.

7.2 Asexual Reproduction

Fragmentation is one of the reasons for the successful colonization of our planet by the mosses. Bryum moss also uses this strategy which can occur when part of the plant breaks off and grows into new, but genetically identical, plants. Fragmentation can happen when an animal or human disturbs the plant, by the wind or other forces of nature.

Pending review by Olivia Milner, practitioner-scientist with a background in sustainability and education.