The damp, shady floor of deciduous woodland is an ideal habitat for many ferns. Hard to spot in winter, their fronds uncurl in spring to form a feathery summer carpet.
Woodland ferns die back in the winter, their dead fronds protecting the crown (or growing point) of each plant during the most severe weather. In late spring, the curled young fronds – known as crosiers – begin to appear. Different species unfurling at different times.
Typical woodland species include the buckler, shield and male ferns, and the delicate lady fern. They are seen at their best in midsummer, when their fronds are fully expanded. Looking rather like large green shuttlecocks, the plants form a feathery carpet on the woodland floor. It is at this time of year that the contrast is most apparent between the abundance of these ferns in woodland – where they may form a lush, almost tropical, cover – and their scarcity in the surrounding fields and moorland. However, although typical of woods, these ferns are also found in similar, favourable conditions elsewhere-in damp, shady hedgerows for example, or on open, rocky hillsides or even on the coast. Bracken is a marked exception. A very invasive species, it is found not only along woodland edges and in clearings, but also spreading over the surrounding pastureland as well.
Young plantations of conifers or broad-leaved trees are rarely carpeted with ferns, the conditions of light and moisture under the tree canopy being more suitable for grasses and other. Mature conifer woods generally have only scanty undergrowth-or none at ail-but where the trees are some distance apart, ferns are able to establish themselves.
The fronds of such woodland ferns as the male, scaly male, broad buckler, hard shield and soft shield ferns are arranged in a whorl on an erect stem. The lady fern also has an erect stem which may grow quite tall and look like a miniature tree trunk. It is the native species that comes close to the tropical tree ferns in appearance. In contrast, the stem of the narrow buckler fern is horizontal and only a few fronds arise from it at intervals.
The size and appearance of the fronds can vary considerably between one individual and another within any one species. About 50 varieties of the soft shield fern, 70 of the lady fern and as many as 150 of the hart’s-tongue fern have been identified. The varieties cover a remarkable range of form. The proportions of the pinnae or of the whole frond may be different, for example, and sometimes this produces a very feathery, dissected appearance. The fronds may even be branched and their margins incised or wavy. The lady fern exhibits a particularly striking variation in the colour of the frond stalk, which may be anything from pale green to dark brown, or even a bright reddish-brown.
Names and identification
The indusium of a fern is the papery material that normally covers the groups of spore capsules (sori) seen on the underside of fern fronds. Its shape and location is important not only in the classification and identification of ferns, but also in the origin of common names. The indusium’s resemblance to a shield inspecies has led to the name ‘shield ferns’, while the buckler ferns are also named from the shield-shaped indusium, a buckler being a small parrying shield. This name has been used as part of the common name for most Dryopteris species since about I860. However, the two largest Dryopteris species in the British Isles are known as the male fern and scaly male fern. This allusion to masculinity conveys the way in which their robust appearance contrasts with the relatively delicate lady fern.
Differences in shape and texture are also indicated by common names, as seen, for ex-ample, in the soft shield and broad buckler ferns. Both shape and frond texture are reflected in the name of the evergreen hart’s-tongue fern. Local folk names are given to ferns in different parts of the country, and so hart’s tongue is also known as buttonholes (from the appearance of the young sori), sea-weed fern, burntweed, Christ’s hair, long leaf, horse-tongue and lamb-tongue.
Although woodland ferns are found throughout the British Isles, they may be locally rare or very abundant. For example, the hard shield fern is generally more common than the soft shield fern, but in the south of England the soft shield fern is the more abundant of the two. The hart’s-tongue is less common in parts of Scotland where the winter temperature is very low, and where there is no suitably alkaline substrate for it to grow on. The narrow buckler and the lady fern are found mainly in wetter places.
A rare species of Dryopteris, the hay-scented buckler fern (Dryopteris aemula), also grows in deciduous woodland. It is distinguished by the scent of hay it exudes when rubbed, and by the frond stalk which is dark brownish-purple at the base and lighter above. Found mainly in the south-east and south-west of England, and in the west of Wales, Scotland and Ireland, it grows only in broad-leaved deciduous woodland where the tree canopy is high enough to keep the level of humidity high.