(1) chemotype with fatty acids (of the murolic acid complex) (K–, Pd–) is widely distributed both in Europe and North America, presence of norstictic acid (K+ red, Pd+ orange) as an accessory substance has been reported in Great Britain and East Fennoscandia (Purvis et al. 1992, Halonen & Puolasmaa 1995); (2) chemotype without any medullary substances is known from North America (Halonen et al. 1998).
In Estonia both chemotypes are known (n=8 and n=6, respectively) (Tõrra & Randlane 2007).

Shrubby thallus and presence of numerous isidiomorphs are similar to U. subfloridana. Slightly deformed main branches and lack of any papillae are the diagnostic features of U. hirta. Medullary chemistry – presence of fatty acids as main compounds – is of help to verify the identification.
Clerc (2007) declared recently that U. hirta lacks isidiomorphs, and young fibrils can be mistakenly treated as isidiomorphs.

Europe (map legend)
Corticolous and lignicolous, prefers acid bark (Fos & Clerc 2000). Reported in Europe: Albania, Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, Germany, Great Britain, Hungary, Island, Italy, Latvia, Lithuania, Luxembourg, Norway, Poland, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine.

Estonia
Mainly grows on conifers (on Pinus 36% of examined specimens, on Picea 34%, on other 10%) and lignum (9%); deciduous trees are seldomly inhabited by this species. Very frequent in Estonia, found in all regions both in forests, open landscapes (wooded meadows, bogs, alvars, seashore areas) and in areas of human activities (Tõrra & Randlane 2007).