FORKED SPLEENWORT

Asplenium septentrionale 

Asplenium septentrionale - Forked Spleen

A rare species of fern that has experienced a rapid decline and has a high risk of extinction in England.

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

  • Cause of decline: Over-collecting during the Victorian period, over or under shading, encroachment of competing vegetation, & potentially pressures from a warming climate

Background 

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.

Ecology and Conservation

Forked Spleenwort is epipetric (growing on rocks) and can be found in crevices of rocks, around boulders and on cliffs on a variety of substrates, including granitic rocks & limestone. In these situations it is generally found in areas with small cracks and crevices which are small enough to prevent larger vascular plants from colonising. 

This distinctive fern has long slender, almost grasslike leaves which can form dense clusters. The fronds are monomorphic and can grow up to 8cm, and often, but not always, have forked tips. Blades are green turning purple to brown at the base, and sori are linear and covered in pale indusia.

Forked Spleenwort is evergreen and long-lived, but does exhibit some dieback at the end of summer. Like other ferns it has a double generational lifecycle, but little is known about its gametophyte stage.

Our Work

We remain very concerned about the survival of this species in England, with both sites showing population decline in recent years. As well as annual monitoring, we liaise with land managers to ensure management is effective in removing over-shading & competing vegetation. 

Our future aims include re-surveying all Welsh sites to investigate its success, and hopefully provide insight into habitat preferences and requirements. This will advise whether an introduction in England is possible to augment the native populations.