Asplenium viride Huds.
Habitat: Crevices and talus of calcareous rock. [Conifer forest (forest, upland)]
Range: Circumboreal, southern Greenland, Eurasia. In North America, Newfoundland to Alaska south to Cape Breton, Maine, Vermont, New York, Ontario, Wisconsin, Colorado, and California.
Aids to Identification: Green spleenwort is a small, delicate fern with linear fronds, 2-15 cm long, 1-2 cm wide. It is once pinnate, the pinnae about twice as long as wide and irregularly toothed. In general, it is smaller, greener, and more fragile than the more common maidenhair spleenwort (Asplenium trichomanes). It can be distinguished from other Asplenium species by its green rachis with dark base, and stipe about 1/3 the length of the narrow, once-pinnate frond.
Ecological characteristics: The ecology of this species, other than its apparent preference for calcareous rocks in cool, moist areas, is largely unknown. Though it is rare throughout its range, occurring often in widely separated locations, it may be very locally abundant. It appears vigorous and thriving at its one known Maine site; here it is growing on a serpentine outcrop where a small amount of calcium is leaching out of associated rocks and precipitating on some cliff surfaces.
Phenology: Fruits June - September. Nearly evergreen, the frond persisting long before withering.
Synonyms: Asplenium trichomanes-ramosum L.
Known Distribution in Maine: This rare plant has been documented from a total of 2 town(s) in the following county(ies): Somerset.
Reason(s) for rarity: Southern limit of range, restricted habitat.
Conservation considerations: Without detailed information on this species' response to openings, the prudent course would be to avoid harvesting in the immediate vicinity of its ledge habitat.