Description: Known only from the Killarney area of County Kerry P. horrescens is a small (to 4cm diam.), rosette-forming, foliose species. The frequently overlapping lobes have a grey-white upper surface sprinkled with coral-like or flattened isidia mixed with black, hair-like cilia which make it unmistakable in the field. The medulla is C-. It does best on acid-barked broadleaved trees and shrubs such as oak, alder and leggy gorse near humid woodland sites and along river valleys. In Ireland, it has spread to lakeside boulders.

Key Identification Features:

• The mixture of isidia and cilia on the lobes distinguishes it immediately from P. minarum (which is also medulla C+ red) and the much larger Parmotrema crinitum which lacks isidia altogether
• Acidic bark near old, humid woodland habitats are the conditions most favoured.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Hypotrachyna horrescens at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Hypotrachyna horrescens at iNaturalist World Species Observations database.