Asplenium trichomanes L. subsp. pachyrachis (Christ) Lovis & Reichstein
(Syn.: Asplenium csikii Kümmerle & Andras.) [Aspleniaceae, Pteridophyta]

The Maidenhair Spleenwort (Asplenium trichomanes L.) is present throughout Luxembourg and quite frequent in natural rock habitats, as well as on walls of all types. Generally two subspecies of Asplenium trichomanes are distinguished: the rare subsp. trichomanes, growing on silicious rocks, and the common, rather calcicole subsp. quadrivalens. A third subspecies, Asplenium trichomanes subsp. pachyrachis (Lobed Maidenhair Spleenwort) - found in Europe at scattered locations - is known for Luxembourg since the early 1990-ties. Until 2001 only a few sites where known in Luxembourg, almost exclusively in the 'Petite Suisse' area.

The plants of Asplenium trichomanes subsp. pachyrachis [Photo 1] are usually smaller and of paler coloration than those of subsp. quadrivalens. They always form a flat rosette of fronds which spread closely over the rock face, in a 'starfish' manner. The pinnae, usually subtriangular or even hastate are often overlapping, which gives each frond a congested overall appearance [Photo2]. Generally longer and more distinctly lobed than in the other subspecies, the pinnae are characterised by an often deeply crenately toothed margin with a conspicuous hyaline border.

Asplenium trichomanes subsp. pachyrachis can hybridise with subsp. quadrivalens, forming a vigorous plant with a more upright habit than subsp. pachyrachis and distinctly intermediate between the parents. It is known as Asplenium trichomanes L. nothossp. staufferi Lovis & Reichstein [Photo 3]. This hybrid is easily found in areas where the two parents are present and grows on natural rocks as well as on man-made walls. 

A rapid investigation of natural sandstone outcrops, buildings, walls, … showed, that Asplenium trichomanes subsp. pachyrachis is rather common in the sandstone area. Here it occurs on natural, often vertical rock surfaces, in crevices on steep rocks, as well as on sandstone walls. At present date, more than 70 sites in 52 square kilometres are known. Most of the sites occur in the 'Petite Suisse' area, but the Lobed Maidenhair Spleenwort is present in the whole sandstone area as far as Luxembourg-City. The results of the investigation, with a description of the taxon, the distribution and status in Luxembourg can be found in: Krippel, Y., 2003. - Aire de répartition et statut d'Asplenium trichomanes L. subsp. pachyrachis (Christ) Lovis & Reichstein (Aspleniaceae, Pteridophyta) au Luxembourg. - Bull. Soc. Nat. luxemb. 104: 3-12.