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Common Name: Spiny Wood Fern

General Information

Dryopteris expansa is a Fern up to 0.40 metres tall.
It is harvested from the wild for local use as a food, medicine and source of materials.

Known Hazards

Although we have found no reports for this species, a number of ferns contain carcinogens so some caution is advisable[].
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[]. 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.

Botanical References

Range

Northern Temperate Zone, including Britain.

Habitat

Cool moist woods, often on rotting logs and tree stumps[].

Properties

Edibility Rating
Medicinal Rating
Habit	Fern
Height	0.40 m
Cultivation Status	Wild

Cultivation Details

An easily grown plant[], it prefers an acid to neutral soil, succeeding in ordinary fertile soil in a shady position[, ]. Prefers a moist soil[].
Closely related to D. dilatata and hybridising where their ranges meet to produce D. x ambroseae.
Members of this genus are rarely if ever troubled by browsing deer[].

Edible Uses

Root - raw or cooked[]. Baked and then peeled before being eaten[]. 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[]. 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[].
The young shoots, harvested in spring before they have fully unfurled, can be cooked and eaten[]. They can be added to soups[].

Medicinal

A poultice of the pounded roots has been applied to cuts[].
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[].

The root contains ‘filicin’, a substance that paralyses tapeworms and other internal parasites and has been used as a worm expellent[, , ]. 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[]. An oily purge, such as caster oil, increases the absorption of the fern root and can be dangerous[]. The root is harvested in the autumn and can be dried for later use, it should not be stored for longer than 12 months[]. This remedy should be used with caution and only under the supervision of a qualified practitioner[]. The root is toxic and the dosage is critical[]. See also the notes above on toxicity.
The root is also used in the treatment of dandruff[, ].

Other Uses

An infusion of the leaves has been used as a hair wash[].

Propagation

Spores - can be sown at any time of the year in a greenhouse. Surface sow on a sterilised compost and keep moist, possibly by placing the pot in a plastic bag. Germinates in 1 - 3 months at 20°c. Pot up small clumps of the plants when they are large enough to handle and grow on in a shady part of the greenhouse until large enough to plant out.
Division in spring. Larger clumps can be replanted direct into their permanent positions, though it is best to pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the spring.