Rim Lichens

(Lecanora spp.)

Rim Lichen (Lecanora sp.)
Photo by Luciearl

Lecanora is a very large genus of crust-forming (crusticose) lichens known by the common name Rim Lichens. It has a worldwide distribution, occurring on every continent including Antarctica. There are about 500 species of Lecanora worldwide, 171 species in North America, and at least 52 species in Minnesota.

Some species grow on rock, other species grow on trees. The photosynthetic partner (the photobiont) is green algae.

The genus name Lecanora is from the Greek lekanon (a small bowl) and ora (form, beauty).


Lecanora is a large crusticose lichen. It is attached to a substrate, usually a rock or a tree, rarely immersed in the substrate. When wet it can usually be removed intact with a knife.

The vegetative body (thallus) is granular, like grains of sugar. This is best seen with magnification with a 10x lens. It is sharply divided into islands separated by cracks (areolate). It may be crusticose in the center but lobed and pleated on the edges, or it may be shield-like.

The spore-bearing reproductive structure (apothecium) is disk-like and variously colored. It usually has a rim of dead algal cells the same color as the thallus. It is usually conspicuous, but in some species it is reduced or absent. The sac-like cell (ascus) contains 8 ascospores. It is colorless and is not divided by walls.

Lichens of the genus Lecanora are easily recognized by their distinct apothecial discs. However, many look alike, and identifying them to the species level often requires complex micro-chemical tests.


Distribution Map



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

  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Phylum Ascomycota (sac fungi)  
  Subphylum Pezizomycotina  
  Class Lecanoromycetes (common lichens)  
  Subclass Lecanoromycetidae (shield lichens, sunburst lichens, rosette lichens, and allies)  


Lecanorales (shield lichens, rim lichens, and allies)  


Lecanoraceae (rim lichens, disc lichens, and allies)  

Subordinate Taxa


Appalachian Powdered-Rim (Lecanora appalachensis)

Beaded Rim Lichen (Lecanora cinereofusca)

Beech Rim Lichen (Lecanora glabrata)

Black-eyed Rim Lichen (Lecanora circumborealis)

Brown-eyed Rim Lichen (Lecanora allophana)

Bumpy Rim Lichen (Lecanora hybocarpa)

Common Rim Lichen (Lecanora pulicaris)

Dusted White-Rim (Lecanora chlarotera)

False-Abrasion Rim Lichen (Lecanora pseudistera)

Frosted Rim lichen (Lecanora caesiorubella)

Fused Rim Lichen (Lecanora symmicta)

Granite-speck Rim Lichen (Lecanora polytropa)

Greenish Yellow Rim Lichen (Lecanora varia)

Hagen’s Rim Lichen (Lecanora hagenii)

Imshaug’s Rim Lichen (Lecanora imshaugii)

Intricate Rim Lichen (Lecanora intricata)

Mapledust Lichen (Lecanora thysanophora)

Mealy Rim lichen (Lecanora strobilina)

Mortar Rim Lichen (Lecanora dispersa)

Perplexed Rim Lichen (Lecanora perplexa)

rim lichen (Lecanora albella)

rim lichen (Lecanora argentata)

rim lichen (Lecanora argentea)

rim lichen (Lecanora cadubriae)

rim lichen (Lecanora carpinea)

rim lichen (Lecanora cateilea)

rim lichen (Lecanora confusa)

rim lichen (Lecanora densa)

rim lichen (Lecanora epanora)

rim lichen (Lecanora expallens)

rim lichen (Lecanora flotoviana)

rim lichen (Lecanora frustulosa)

rim lichen (Lecanora fuscescens)

rim lichen (Lecanora hypoptoides)

rim lichen (Lecanora laxa)

rim lichen (Lecanora marginata)

rim lichen (Lecanora meridionalis)

rim lichen (Lecanora minutella)

rim lichen (Lecanora nothocaesiella)

rim lichen (Lecanora saligna)

rim lichen (Lecanora subimmergens)

rim lichen (Lecanora subintricata)

rim lichen (Lecanora subrugosa)

rim lichen (Lecanora tristiuscula)

Shameless Rim Lichen (Lecanora impudens)

Smoky Rim Lichen (Lecanora cenisia)

Sunken Rim Lichen (Lecanora oreinoides)

Valois Rim Lichen (Lecanora valesiaca)

Varying Rim Lichen (Lecanora argopholis)

White Rim Lichen (Lecanora rupicola)

Wisconsin Rim Lichen (Lecanora wisconsinensis)

Wood-spot Rim Lichen (Lecanora albellula)






Common Names


Rim Lichens












An open, disk-shaped or cup-shaped, reproductive structure, with spore sacs on the upper surface, that produces spores for the fungal partner of a lichen. Plural: apothecia.



Crusty; referring to lichens in such close contact with the rock surface (substrate) that it appears sprayed on like paint.



The photosynthetic partner of a lichen; either green algae or cyanobacteria.



In lichens: The vegetative body of a lichen composed of both the alga and the fungus. In liverworts: a flat, relatively undifferentiated plant body. Plural: thalli.


Heterogenous Genus

As originally defined in 1926, Lecanora was an artificial assemblage of species. Over the years several genera have been split off. However, Lecanora remains a heterogeneous genus, and further splitting is both necessary and inevitable.


Species Identification

It is relatively easy to identify a rim lichen in the genus Lecanora. However, identification to the species is problematic. Many of the North American species look alike and can be identified only with chemical testing.

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Lichen found on large boulder near pond. Covered most of the rock.

    Rim Lichen (Lecanora sp.)   Rim Lichen (Lecanora sp.)  
MinnesotaSeasons.com Photos








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Location: Lake Shore

Lichen found on large boulder near pond. Covered most of the rock.

Rim Lichen (Lecanora sp.)

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Created: 11/28/2021

Last Updated:

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