Powder-edged Speckled Greenshield

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Powder-edged Speckled Greenshield Is a medium-sized, common, and very widespread lichen. It occurs in Europe, Asia, Africa, and North and South America. It occurs across the United States, throughout Mexico, and in southern Canada. It is very common in Minnesota. It grows on the bark and wood of both hardwoods, including maple, New Jersey tea, ash, walnut, cherry, oak, sumac, locust, and willow; and on conifers, including balsam fir, eastern redcedar, spruce, pine, and Douglas fir. It very rarely grows on rock.

The vegetative body (thallus) is up to 4¾″ in diameter, leaf-like (foliose), and divided into lobes. It may be closely pressing against the surface (appressed), or growing with the bark so that it can't be removed with a knife without fragmenting (adnate). It is attached to the substrate (bark or wood) by numerous tufted anchoring structures (rhizines). The rhizines are short, unbranched, and the same color as the lower surface of the thallus. They are dense toward the center and usually absent near the margins. The lobes are narrow, irregular, flat, and ⅛″ to 5 ⁄16″ wide. Adjacent lobes touch but are not fused together. The upper surface is smooth or slightly wrinkled, pale green or yellowish-green to greenish-yellow, and frequently has white blotches. The underside is black to dark chestnut brown, except near the edges, which is sometimes pale brown. The margins are crescent-shaped and are densely covered with white reproductive granules (soredia), giving them a powdered look. This is the feature that gives the lichen its common name. The upper side does not have soredia.

Spore-producing structures (apothecia) are rarely produced. When present, they are dark brown, saucer-shaped, deeply concave, and 1 ⁄16″ to ¼″ (2 to 6 mm) in diameter.

Trees

Foliose

Hardwoods, including maple, New Jersey tea, ash, walnut, cherry, oak, sumac, locust, and willow; and conifers, including balsam fir, eastern redcedar, spruce, pine, and Douglas fir.

Sources

4, 24, 26, 29, 30, 77.

Very widespread and very common

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Location: Cass County