Plant of the Week

USDA Plants distribution map for the species.
Range map of Bryum argenteum. USDA PLANTS Database.

Bryum argenteum, old man’s beard.
Bryum argenteum, silvergreen bryum moss. Photo by David Nicholls.

Silvergreen Bryum Moss (Bryum argenteum)

By Robinson Sudan

Physical Characteristics: Bryum argenteum is easily recognizable with its typical moss growth pattern: low cylindrical shoots (typically less than 1 centimeter) of compact tufts. The reproductive structures appear on stalks raised above the photosynthetic parts of the plant (roughly 1 centimeter) between autumn and spring.

Growing Conditions and Distribution: Bryum argenteum is a cosmopolitan species common to urban areas where it can be found between cracks on sidewalks, poor soil, and rocks. It can be found in more natural settings as well, however it has come to thrive better in anthropogenic habitats.

Conservation Status: Because of its cosmopolitan distribution, wide range of habitats, and propensity to thrive in human dominated landscapes, Bryum argenteum is not recognized as threatened.

Pollinator Information: Most plant species alive today are dominated by what is called the sporophyte phase of the plant life cycle. Quite unlike most plants, but as with all true mosses, Bryum argenteum is dominated by the other phase of life called the gametophyte stage. As such, the reproductive structures of this and all mosses do not have the same structures as flowering plants and do not produce pollen of any kind. Instead, the sperm are produced by structures called antheridia and released where they swim to the female structures called archegonia. Once an egg has been fertilized, the characteristic capsule on a stalk is produced which contains spores that are released once they mature.

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