Easily confused with : Parsley Fern but that has only one groove on the upper-surface of the mid-rib rather than the two of Black Spleenwort.
Western Black Spleenwort (Asplenium onopteris) grows only in Ireland, again on limestone ricks. It has more delicate and narrower yellowish-green leaves with the secondary leaflets narrowly pointed throughout their length. It has longer stalks with the reddish-brown coloration extending to the mid-ribs.
Occupies niches in walls, rocks, and hedge-banks. Most common in the West of the UK.
There seems to be a quite pronounced variation in the fronds of Black Spleenwort, even on other websites, many looking un-like the drawings in Blamey, Fitter and Fitters 'Wildflowers of Britain and Ireland' book, and this includes the specimen shown here. These differences reflect real variations in appearance, perhaps because the brighter green ones with broader and rounder pinnae are growing in a more open place, whereas the darker green ones with narrower pinnae are growing in the semi-shade? Or maybe it reflects differences in time, the brighter green might be older and the duller green newer?
However, the numerous recorded hybrids of Black Spleenwort cannot account for this apparent variability because they are all very rare and none occur anywhere near the North West of England, and nearly all of the once few locations are now devoid of any hybrids.
Hybridizes with :
Forked Spleenwort (Asplenium septentrionale) to produce Asplenium × contrei only ever found in one hectad in North Wales, not been seen since 1999.
Hart's-tongue (Asplenium scolopendrium) to produce Asplenium × jacksonii only found in one or two hectads in Cornwall and an island SW of Penzance.
Irish Spleenwort (Asplenium onopteris) to produce Asplenium × ticinense only found in one or two hectads in Southern Ireland.
Lanceolate Spleenwort (Asplenium obovatum) to produce Asplenium × sarniense which has once to be found in Ireland in one hectad , but now only in one or two islands south west of Penzance.
FERNS ALTER THE SOIL CHEMISTRY
This fern, and others like it such as Rusty-back Fern (Asplenium ceterach) and Maidenhair Spleenwort (Asplenium trichomanes), have a propensity to generate phenolic and phenolic acid compounds in the soil in which they grow. compounds such as
p-Hydroxy Benzoic Acid,
Syringic Acid. In concentration terms, roughly a quarter to three-quarters of the amount of these compounds are bound to other compounds in the soil, whilst the remainder, in much smaller amounts (between 10 to 280 times smaller), is free, (un-bound). Thus ferns (or at least these ferns) alter the soil chemistry to suit themselves and to dissuade other plants from colonising the soil.
Likewise, the soil beneath Bracken (Pteridium aquilinum) is altered to include
p-Hydroxy Benzoic Acid,
p-Hydroxy Cinnamic Acid and
The ferns accomplish this by returning secondary metabolites produced within themselves to the soil to cause high concentrations of phenolic compounds in soil humus. They acidify the soil, lowering its pH.