Green Spleenwort (Asplenium viride) is a distinctive small fern often found in specialized environments. This perennial fern typically reaches heights of 8 to 15 centimeters, characterized by its delicate appearance. It thrives in cool, often shaded, and rocky locations. Its name reflects its vibrant green coloration.
Identifying Green Spleenwort
Its fronds are long and narrow, typically 5 to 15 cm in length and up to 1.5 cm wide. These fronds are once-pinnate, meaning the main stalk has leaflets (pinnae) arranged along it. The pinnae are small, usually oval or rhombic, with bluntly lobed or toothed edges.
A distinguishing feature of Green Spleenwort is its stipe (stem) and rachis (the central axis of the frond). The stipe, the stalk connecting the frond to the rhizome, is typically 1-6 cm long and reddish-brown at its base, transitioning to green above. The rachis, or midrib, remains green along its entire length, which helps differentiate it from the similar Maidenhair Spleenwort (Asplenium trichomanes), which has a reddish-brown or nearly black rachis. On the underside of the fronds, the sori (spore-producing structures) appear as single, elongated lines, typically 0.5-1mm long, following the veins. These sori are covered by a thin, whitish indusium, a protective membrane that may be deciduous.
Natural Habitat and Range
Green Spleenwort primarily prefers cool, moist, and shaded rocky habitats. It is frequently found in crevices of calcareous rocks, such as limestone and dolomite, and on talus slopes. The fern shows a strong preference for base-rich or lime-tolerant conditions, often growing in association with moss-covered surfaces.
This fern is often found in mountainous regions or at higher altitudes. Its global distribution is circumboreal, meaning it is found across the northern temperate regions of the world. Its native range extends through Europe, Western and Central Asia, the Himalayas, and parts of North Africa. In North America, its distribution spans from Newfoundland to Alaska, reaching south into states like Maine, Vermont, New York, Wisconsin, Colorado, and California.
Ecological Role and Reproduction
The reproductive cycle of Green Spleenwort relies on spores, rather than seeds or flowers. Spores are produced in the sori located on the undersides of its fronds, typically ripening from August to November. When mature, these spores are dispersed, often by wind, and can germinate in suitable moist conditions to begin the next stage of the fern’s life cycle.
Green Spleenwort demonstrates adaptations that enable it to thrive in its challenging rocky environments. Its ability to grow in rock crevices allows it to utilize sheltered microclimates that retain moisture and offer protection. This fern is perennial and nearly evergreen, with fronds persisting before withering, contributing to its resilience in its preferred habitats. Green Spleenwort plays a role in stabilizing soil within rock crevices and can provide small microhabitats for invertebrates. While generally widespread, it can be rare in certain parts of its range, reflecting its specialized habitat requirements.