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Usnea is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs.[1]:203 The genus is in the Parmeliaceae family. It grows all over the world.

Members of the genus are commonly called tree's dandruff,[citation needed] woman's long hair,[citation needed] or tree moss,[citation needed], old man's beard, or beard lichen.[1]:203 It resembles Evernia, which is also called tree moss.[2]

Like other lichens it is a symbiosis of a fungus and an alga. The fungus belongs to the division Ascomycota, while the alga is a member of the division Chlorophyta.

Members of the genus are similar to those of the genus Alectoria.[1]:148 A test for the different is that the branches of Usnea are somewhat elastic, but the branches of Alectoeria snap cleanly off.[1]:148

Morphology and reproduction[edit]

As a fruticose lichen, Usnea appears as a shrub-like growth on host trees. It reproduces via vegetative means through fragmentation, asexual means through soredia, or sexual means through ascogonium and spermatogonium.[3] The growth rate of lichens in nature is slow, but the growth rate has been sped up in laboratory conditions where Usnea is being cultured.[4] Usnea looks very similar to Spanish moss, so much so that the latter plant's Latin name is derived from it (Tillandsia usneoides, the 'Usnea-like Tillandsia').


Many species have been described. A three-volume series by Józef Motyka published in 1936 and 1947 distinguished 451 species.[5] Many of these are now regarded as morphological varieties and adaptations to local circumstances. The taxonomic categorization of many members of this genus remains uncertain. The number of recognized species in Finland is decreasing for this reason, from 34 in 1951 to 25 in 1963 and only 12 in 2000.[6] It is now noted as including more than 600 species and being one of the largest genera within the Parmeliaceae.[7] The species Usnea longissima was renamed Dolichousnea longissima in 2004.[8]


Like other lichens, Usnea often grows on sick or dying trees due to the pre-existing loss of canopy leaves, allowing for greater photosynthesis by the lichen's algae; this leads some gardeners to mistakenly blame the lichen for the tree's leaf loss and illness.[9]

Usnea is very sensitive to air pollution, especially sulfur dioxide.[10] Under bad conditions they may grow no larger than a few millimetres, if they survive at all. Where the air is unpolluted, they can grow to 10–20 cm long.


Medical claims[edit]

Prescientific medical systems included use of Usnea in the belief it had healing effects for at least 1600 years.

Usnea was one ingredient in a product called Lipokinetix, promoted to induce weight loss via increase in metabolic rate. Lipokinetix has been the topic of an FDA warning in the USA,[11] due to potential hepatotoxicity, although it is unclear yet if any toxicity would be attributable to the Usnea. Lipokinetix also contained PPA, caffeine, yohimbine and diiodothyronine.

There is reason to believe that Usnea, in high concentrations, could possess some toxicity.[12] The National Toxicology Program is currently evaluating the issue.[13]


Usnea species have been used to create orange, yellow, green, blue and purple dyes for textiles.[14][15]


Usnea barbata has been used in cosmetic production for its antimicrobial and antifungal properties as a preservative and deodorant.[16]


There are about 86 species of Usnea.[17]



  1. ^ a b c d Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, ISBN 978-0-300-19500-2
  2. ^ Jellin, JM; Gregory P., Batz F., Hitchens, K., et al. (2000). "USNEA". Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database (3rd ed.). Stockton, CA: Therapeutic Research Facility. pp. 1048–1049. ISBN 0967613647. 
  3. ^ Marand, Sajan (5 January 2010). "Usnea". A Text Book of Botany: Vol. III. Calicut University. pp. 87–90. Retrieved 6 December 2012. 
  4. ^ "Optimization of Culture Conditions for Lichen Usnea ghattensis G. Awasthi to Increase Biomass and Antioxidant Metabolite Production". Food Technol. Biotechnol. 47 (1): 7–12. 2009. ISSN 1330-9862. 
  5. ^ Motyka, Józef. Lichenum generis usnea. 
  6. ^ Halonen, Pekka (2000). Studies on the lichen genus Usnea in East Fennoscandia and Pasific North America. Oulu, Finland: Oulu University Library. p. 13. ISBN 9514255232. ISSN 0355-3191. Retrieved 6 December 2012. 
  7. ^ Wirtz, Nora; Printzen, Christian; Sancho, Leopoldo G.; Lumbsch, Thorsten H. (1 May 2006). "The phylogeny and classification of Neuropogon and Usnea (Parmeliaceae, Ascomycota) revisited". Taxon 55 (2): 367–376. ISSN 0040-0262. Retrieved 5 December 2012. 
  8. ^ Articus, Kristina (November 2004). "Neuropogon and the phylogeny of Usnea s.l. (Parmeliaceae, Lichenized Ascomycetes)". Taxon 53 (4): 925–934. ISSN 0040-0262. Retrieved 5 December 2012. 
  9. ^ Brodo, Irwin M.; Sylvia Duran Sharnoff; Stephen Sharnoff; Canadian Museum of Nature (2001). Lichens of North America. Yale University Press. pp. 57–58. ISBN 9780300082494. Retrieved 6 December 2012. 
  10. ^ Batty, Lesley C., & Hallberg, Kevin B., ed. (2010). Ecology of Industrial Pollution. Ecological Reviews. Cambridge University Press. p. 49. ISBN 9780521514460. Retrieved 4 December 2012. Usnea spp., at one time widespread and luxuriant, almost entirely disappeared from a major area of England and Wales covering at least 68 000 km² and at least 6 000 km² of lowland Scotland, mainly as a result of the increase in atmospheric pollution. 
  11. ^ "Safety Alerts for Human Medical Products > Lipokinetix". MedWatch: The FDA Safety Information and Adverse Event Reporting Program. U.S. Food and Drug Administration. November 20, 2001. Retrieved 5 December 2012. FDA has received multiple reports of persons who developed liver injury or liver failure while using Lipokinetix. The product contains norephedrine (also known as phenylpropanolamine or PPA), caffeine, yohimbine, diiodothyronine, and sodium usniate. 
  12. ^ Jellin, JM; Gregory P., Batz F., Hitchens, K., et al. (2000). "USNEA". Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database (3rd ed.). Stockton, CA: Therapeutic Research Facility. pp. 1048–1049. ISBN 0967613647. Adverse reactions are uncommon in appropriate amounts. Poisoning can be possible, although signs of poisoning have not yet been described. 
  13. ^ "Testing Status: Usnea lichen 09063". Testing Status of Agents at NTP. National Toxicology Program. Retrieved 5 December 2012. 
  14. ^ Bolton, Eileen M. (1991). Lichens for Vegetable Dying (2 ed.). Julia Bolton Holloway. p. 27. ISBN 9781566590013. 
  15. ^ Casselman, Karen Diadick (2001). Lichen Dyes: The New Source Book. Courier Dover Publications. pp. 33–36. ISBN 9780486412313. 
  16. ^ Ash, Michael; Irene Ash (2004). "Lichen (Usnea barbata) extract". Handbook of Preservatives. Synapse Info Resources. p. 437. ISBN 9781890595661. Retrieved 6 December 2012. 
  17. ^ "PLANTS profile for Usnea (beard lichen)". USDA PLANTS. United States Department of Agriculture, Natural Resources Conservation Service. Retrieved 4 December 2012. 
  18. ^ "Lichens of Wales". Retrieved 3 December 2014. 


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