Spiny Wood Fern, Spreading woodfern

Dryopteris expansa

Physical Characteristics

Dryopteris expansa is a FERN growing to 0.4 m (1ft 4in) by 0.5 m (1ft 8in). See above for USDA hardiness. It is hardy to UK zone 3. The seeds ripen from July to September. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid and neutral soils. It can grow in full shade (deep woodland) or semi-shade (light woodland). It prefers moist soil.

Distribution

Northern Temperate Zone, including Britain.

Habitats

Woodland Garden Dappled Shade; Shady Edge; not Deep Shade;

Edible Uses

Edible Parts: Leaves Root Shoots Edible Uses: Root - raw or cooked[256]. Baked and then peeled before being eaten[257]. The raw root is rather bitter but they develop a sweet taste when cooked and are said by some people to develop a flavour rather like sweet potatoes[256]. The root is best harvested in early autumn. At this time the rhizomes are surrounded by scaly, finger-like projections - if the projections are flat and dark inside then the rhizomes are not good to eat but if they are round, fleshy and light-coloured then they can be eaten[256]. The young shoots, harvested in spring before they have fully unfurled, can be cooked and eaten[257]. They can be added to soups[257].

Medicinal Uses

Anthelmintic Poultice A poultice of the pounded roots has been applied to cuts[257]. We have no other reports for this species, but the following uses apply to many members of this genus and quite probably also to this species[K]. The root contains ‘filicin’, a substance that paralyses tapeworms and other internal parasites and has been used as a worm expellent[4, 172, 238]. It is one of the most effective treatments known for tapeworms - its use should be immediately followed by a non-oily purgative such as magnesium sulphate in order to expel the worms from the body[238]. An oily purge, such as caster oil, increases the absorption of the fern root and can be dangerous[238]. The root is harvested in the autumn and can be dried for later use, it should not be stored for longer than 12 months[238]. This remedy should be used with caution and only under the supervision of a qualified practitioner[238]. The root is toxic and the dosage is critical[238]. See also the notes above on toxicity. The root is also used in the treatment of dandruff[4, 172].

Known Hazards

Although we have found no reports for this species, a number of ferns contain carcinogens so some caution is advisable[200]. The fresh plant contains thiaminase, an enzyme that robs the body of its vitamin B complex. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase[172]. However, there have been reports for other species of ferns suggesting that even cooked fronds can have a long term harmful effect. Some caution is therefore advised.