Polystichum setiferum (Forssk.) T. Moore ex Woyn., Soft Shield-fern
Account Summary
Native, common, very widespread and locally abundant. Submediterranean-subatlantic.
1860; Smith, Rev Prof R.W.; Co Fermanagh.
Throughout the year.
Growth form and recognition
This large, common rhizomatous fern develops dense shuttlecocks of many fronds. In the middle part of the frond the base of every pinnule has a larger lobe, ie the ultimate segments are highly asymmetrical at their base (Webb et al. 1996; Rich & Jermy 1998, p. 29). This feature, plus the soft texture (always best appreciated by touching the plant), and the grass-green colour of mature fronds make this an easily recognised species, although some individual plants whose texture is less soft will need to be examined more closely to distinguish them from P. aculeatum (Hard Shield-fern) (Page 1997).
The fronds expand in late April or early May and are generally wintergreen with us in Ireland, the old fronds only dying off as the new fronds begin to unfurl. (In colder parts of Britain the fern is regarded as semi-evergreen, fronds dying off after the first hard frost.) Sporing is copious and begins in July or early August. It may continue until the fronds wilt and collapse in the following spring.
Preferred habitats
Soft Shield-fern occurs on a variety of moderately acidic to neutral, damp but not wet soils of medium base-status. The species is sometimes described as a moderate calcicole (T.D. Dines, In: Preston et al. 2002). It is very common and widespread, and under suitable conditions it can dominate the ground layer in humid woods at low altitude. P. setiferum is generally absent from upland areas above c 200 m, and also from strongly acidic peaty ground. Apart from damp mixed deciduous woods, the most frequent habitats of P. setiferum in Fermanagh as elsewhere in Britain and Ireland are on slopes in scrub, along hedgerows, riverbanks and in similar sheltered, shady, damp, but well-drained places.
Fermanagh occurrence
In Fermanagh, this large, rhizomatous fern is common and very widespread having been recorded in 344 tetrads, 64.6% of those in the VC. In terms of tetrad frequency this makes it the eighth most widespread fern in our survey area.
Irish occurrence
Soft Shield-fern is very common throughout most of Ireland except in the more exposed, strongly acidic, constantly wet peatlands of the W & C where it becomes decidedly rare or absent (Jermy et al. 1978; An Irish Flora 1996; New Atlas).
British occurrence
Soft Shield-fern is abundant in suitable sites in SW England and SW Wales, but as one moves either east or northwards it becomes steadily rarer, until in Scotland it is virtually confined to western coasts. The most northerly point P. setiferum reaches anywhere in the world is near Ullapool on the west coast of Scotland (Jermy et al. 1978; New Atlas).
European and world occurrence
Overall P. setiferum is very definitely an Atlantic or oceanic species, most abundant along the Atlantic coastline, but occurring inland throughout W and S Europe and along the northern shore of the Mediterranean, becoming more discontinuous further east but reaching the Caspian Sea area. It occurs on all the islands in the Azores, and further south reaches Madeira and the Canary Islands (Jalas & Suominen 1972, Map 121; Hultén & Fries 1986, Map 62; Page 1997; Vertag 2002).
Hybrids
P. setiferum hybridizes with P. aculeatum to form P. × bicknelli, which has been recorded once in Fermanagh (see our account of this hybrid).
Names
The genus name 'Polystichum' is derived from two Greek words 'polus', 'many', and 'sticos' or 'stichos', 'row' or 'file'. The genus name thus translates as 'many rows', a reference to the regular rows of sori on the fertile frond (Gilbert-Carter 1964). The specific epithet 'setiferum' means 'bristle-bearing' and is derived from the Latin words 'seta' or 'saeta' meaning 'a bristle' or 'a stiff hair', and 'fero' meaning 'to bear' or 'to carry' (Gilbert-Carter 1964).
In past years, the general population did not distinguish any species of Polystichum other than P. lonchitis (Holly-fern), so there are no folk uses, nor any English common names other than obvious, invented 'book names' (Step & Jackson 1945). The name 'Shield fern' is given because the circular, centrally stalked (peltate) indusium that protects the young sorus is considered reminiscent of the Medieval circular Buckler shield.
Threats
None.