SafePlants

Xanthoria parietina: The Common Orange Lichen

Xanthoria parietina is a vibrant foliose lichen, known for its distinctive orange color and widespread distribution. It is often referred to by several common names.

Common Names:

• Common Orange Lichen
• Yellow Scale
• Maritime Sunburst Lichen
• Orange Lichen
• Orange Wall Lichen
• Sunburst Lichen
• Golden Shield Lichen
• Shore Lichen

Taxonomy and Nomenclature:

• Scientific Name: Xanthoria parietina
• Genus: Xanthoria
• Family: Teloschistaceae

Distribution and Habitat:

• Xanthoria parietina has a wide distribution and can be found growing on rocks, concrete, trees, and even tombstones.
• It is often prolific near cattle farms due to its preference for ammonia.
• It is commonly found on the coast and in mountainous areas.
• Specific locations include the Western Isles, New Zealand coastal rocks, Humboldt Lagoons State Park (California), and Mount Washburn Trail (Yellowstone National Park, Wyoming).

Morphological Characteristics:

• Xanthoria parietina is a foliose lichen, forming large, rounded patches that can reach up to 10 cm across.
• It has wide, round-lipped marginal lobes.
• The thallus (body) color ranges from yellowish-green to golden-yellow or orange, and may appear grey in shaded areas.
• It lacks isidia or soredia.
• Apothecia (fruiting bodies) are usually present, featuring a dark orange disc surrounded by a lighter edge.

Ecological Role:

• Xanthoria parietina can be especially prolific in certain environments, forming an orange lichen belt.
• It can grow in profusion near seabird colonies and on hunting perches of birds.
• It favors rough, water-retentive, naturally alkaline bark.

Interactions with Other Organisms:

• Lichens are symbiotic associations between a fungus and an alga. The alga is contained within the hyphae.

Quirky Facts:

• The orange color of Xanthoria parietina is due to the production of the pigment parietin.
• The color of lichens can vary depending on the amount of sun or rain; orange or yellow lichens in shade may appear green.
• The pigment parietin found in Xanthoria parietina may have potential as an anti-cancer drug.
• Bright orange lichen is sometimes seen as a sign of a healthy forest.

Further Information:

• Microchemical Methods for the Identification of Lichens by Alan Orange is a guide to chemical use and precautions.