Polypodium vulgare L. s.s., Polypody

Account Summary

Growth form and identification

Some of the earlier Fermanagh records of this rhizomatous species were determined from herbarium vouchers in BEL by Paul Hackney. Typically P. vulgare s.s. has narrow, rather leathery, evergreen, parallel-sided fronds with the lowest pair of pinnae not bent forward (ie not inflexed) like those of P. interjectum (Intermediate Polypody) (the allohexaploid derivative of its hybrid with P. cambricum (Southern Polypody)).

New fronds of P. vulgare s.s. are produced in early summer and the species, which is a tetraploid, has numerous pairs of naked sori in the upper portion of the frond which ripen their spores in mid-summer (Jermy & Camus 1991).

Preferred habitats

In contrast to the two other species of the genus in our survey area, P. vulgare s.s. is a definite calcifuge. It typically grows on cliff ledges and in rock crevices on steep, peaty banks, in between the rocks in old, dry-stone walls or along the tops of such walls, and it also occurs as an epiphyte on the bark of mature deciduous trees in damp woods.

A study of the preferences of a number of ferns with respect to soil reaction carried out in W Europe by Koedam et al. (1992) found that soil taken from the root mass of P. vulgare s.s. had a median pH of 4.13, and consequently the plant was regarded by these workers as 'acidiphilous' (ie acid loving, or acid tolerant). Such species are adapted to soils with high levels of exchangeable aluminium and hydrogen, and relatively low levels of exchangeable calcium.

British and Irish occurrence

P. vulgare s.s. is the most common form of Polypody recorded in both Britain & Ireland, and in N Ireland it is recorded in almost every hectad.

Fermanagh occurrence

In Fermanagh, this is the most common and widespread species of polypody, having been recorded so far in 94 tetrads, 17.8% of those in the VC. Nevertheless, since many field recorders work at the species aggregate level and do not distinguish the separate Polypodium species, we regard it as definitely under-recorded. As the tetrad distribution map indicates, this form is widely scattered throughout Fermanagh, but more prevalent in the wetter, more acid, rocky upland environments of the Western Plateau.

Threats

None.

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