Spleenworts
What are they?
Ferns are primitive plants that evolved before the flowering plants and reproduce sexually by means of spores rather than seeds. This page covers the spleenworts, a family of generally small species, which are most frequently to be found growing on walls in our region. Most of the spleenworts are rather different to the traditional idea of a fern and lack the multi-divided leaves that are so typical of larger, woodland or wetland ferns.
Where are they found?
The spleenworts are generally plants of rocky places, a habitat that is absent from East Anglia, so the plants are generally to be found growing from walls, especially the older walls of churches, churchyards, older town centres and stone or brick bridges. Plants generally grow better on the shadier, north facing sides.
Identification
This is an easy group to identify, based on overall leaf shape. All species are evergreen. For ease of describing the various parts, a couple of technical terms are used; the side arms that form the first division of a leaf are called pinnae (singular, pinna), while the secondary divisions of the pinnae are called pinnules, which make up the smallest parts of each leaf.
Hart's-tongue Asplenium scolopendrium
Native. Occasionally found in woodland especially along ditch sides and shady banks, but increasingly more common as a plant of dank corners, old walls, cemeteries and other human-influenced habitats. Commonly found beneath gratings in towns. A very distinctive fern, being our only species with highly glossy leaves that are entire and not at all divided. The spore-bearing sori on the underside of the leaves appear as a series of narrow, dark, parallel lines. This plant is evergreen and the old leaves can get browned and very tattered over winter before the new leaves emerge in spring. Plants may form large clumps with leaves up to 60cm long in shady woodland, but are much smaller when growing on walls.
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Black Spleenwort Asplenium adiantum-nigrum
Native. Widespread but rather local. Almost exclusively found on churches, bridges and other stone-built, man-made structures. Can be very common where it occurs, often forming colonies on stone walls and attaining great heights on church towers! A delicate fern, unusual in this group in having deeply divided leaves with long-tapered tips. Plants in sunnier places often turn golden-bronze in colour.
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Maidenhair Spleenwort Asplenium trichomanes
Native. Widespread but rather local. Almost exclusively found on churches, bridges and other stone-built, man-made structures. The long, narrow leaves with rounded pinnae and black midribs are distinctive.
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Maidenhair Fern Adiantum capillus-veneris
Native in the UK but only an escape from cultivation in East Anglia and occasionally found in urban habitats. The leaves bear fan-shaped pinnae, carried on fine, hair-like, blackish stems are very distinctive. This plant os probably much better known as a houseplant in the UK.
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Wall-rue Asplenium ruta-muraria
Native. Widespread but generally uncommon on walls, bridges and old buildings, becoming a little more common northward and westward in Norfolk. A very distinctive fern that has a blue-green colour to its leaves, whichresemble the leaves of garden rue (Ruta graveolens).
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Rustyback Fern Asplenium ceterach
Native. A rare species in East Anglia, recorded from fewer than 20 sites in the region on old walls, cemeteries and other human-influenced habitats. The leaves have distinctive pinnae that are broadest at the base and merge into the midrib without stalks. The underside of the leaves are covered in papery scales and turn rust-coloured as the spores ripen.
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