FORKED SPLEENWORT

Asplenium septentrionale 

Asplenium septentrionale - Forked Spleen

A rare species of fern that has experienced a rapid decline in the South of England.

  • Rarity: Known from only 2 sites in the South of England

  • Cause of decline: Overcollecting during the Victorian period, over or under shading, and the encroachment of competing vegetation.

Forked Spleenwort is a unique fern amongst rock-dwelling pteridophytes, with its almost grasslike delicate fronds, making it instantly recognisable.

Although never common in England, its current occupation of just two sites gives great cause for concern for its long-term survival. Our work is focussing on keeping these two populations extant, while collecting more data about its occurrence in Scotland and Wales; both to ensure its wider national survival, and learn more about its ecology.

Historically it has been threatened by sites becoming scrubbed over, and its reliance on newly created or maintained rock faces. In recent years the run of exceptionally hot summer periods and the detrimental impact this has had on plants in England have given cause for concern that climate change may also have a large impact on this and other species which occupy bare rock niches.

A distinctive fern with long slender, almost grasslike leaves. It can form dense clusters. The fronds are monomorphic, with no difference between fertile and sterile fronds. The leaf blades are narrow (<0.5cm), usually 4-8cm long and stiff, with a leathery texture. They can grow up to 8cm and often, but not always, have a forked tip. Blades are green turning to a purple/brown at the base. The sori are linear, covered with pale indusia with entire edges.

Forked Spleenwort is evergreen and long-lived, but does exhibit some dieback at the end of the summer growth season, especially in droughtprone situations. Like other ferns it has a double-generational lifecycle, but little is known or published about the precise ecological needs of the gametophyte. It is likely to develop in cracks in rock faces before the adult sporophyte emerges.