Vascular Plants of North Carolina
Account for Rusty Cliff Fern - Woodsia ilvensis   (L.) R. Brown
Members of Woodsia with account distribution info or public map:
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Section 2 » Order Polypodiales » Family Woodsiaceae
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Author(L.) R. Brown
DistributionLimited just to the northernmost Mountains, known from just three counties -- Ashe, Alleghany, and Surry.

This is a Northern species, ranging from Canada south to New England, NY, and MN, south in the Appalachians just to extreme northwestern NC. KY and TN lack verified records.
AbundanceVery rare, known from just four sites, with only the two in Ashe County in good condition, according to the NCNHP database. This is a State Endangered species.
HabitatIn NC, this species is essentially limited to rather high elevation rock outcrops, dry and exposed (such as High Elevation Rocky Summits as well as cliffs), where the rocks are mafic, and thus the soil in the crevices is of rather high pH.
PhenologyFruits from June to September.
IdentificationThis is a very rare plant in the state, found readily at only one site on public conservation land. This is a somewhat smaller species than the similar W. appalachiana, another rare rock inhabitant of the mountain region. The stipe is brown and hairy, with a joint near the base. The blade is lanceolate, tapered to the apex and only slightly tapered near the base; the blade is only about 5 inches long and just 1.5 inches wide, being pinnate-pinnatifid cut. Thus, it is not as deeply dissected as is W. appalachiana, which has distinct and separated pinnules on each pinna, as opposed to pinnules barely cut to the midrib in this species. The habitats of the two differ, as this species grows at fairly high elevations (mainly over 3500 feet) and on mafic rock types, whereas the other grows in the lower mountains on more acidic soils in crevices of felsic rock types. Separation of the three Woodsia species, as well as the several Cystopteris species, can be quite difficult without a hand lens. Woodsia species have "the indusium divided into a series of scale-like or hair-like structures, attached below the sorus; Cystopteris has an undivided indusium, pocket-like or hood-like, attached around one side of the sorus. Woodsia has persistent dark petiole bases; in Cystopteris the petiole bases are deciduous. Woodsia has the final veinlets not reaching the margins; Cystopteris veins do reach the margin." (Weakley 2018). Within Woodsia, this species can be separated from the more widespread W. obtusa by having "Pinnae with numerous long whitish scales", versus W. obtusa having "Pinnae without scales, a few broad scales on the midrib" (Wofford 1989). W. ilvensis has the petioles "with a distinct joint about 1-3 cm above the base" (Weakley 2018), such that former blades leave a rather even stubble, as opposed to the other two that lack such a joint, and the former leaves having an uneven stubble of broken stipes.
Taxonomic CommentsNone

Other Common Name(s)Rusty Woodsia
State RankS1
Global RankG5
State StatusE
US Status
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B.A. SorriePhoto taken 1981, Mount Toby, MA. Photo_non_NCPhoto_non_NC
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