Crown Wood-Fern

Dryopteris crassirhizoma

Physical Characteristics

Dryopteris crassirhizoma is a FERN growing to 1 m (3ft 3in). See above for USDA hardiness. It is hardy to UK zone 6. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid and neutral soils. It can grow in semi-shade (light woodland). It prefers moist soil and can tolerate drought.

Distribution

E. Asia - Japan, Korea, Manchuria.

Habitats

Woodland Garden Dappled Shade; Shady Edge;

Edible Uses

Edible Parts: Leaves Edible Uses: Young fronds[177]. No further details, but we would advise caution. See the notes above on toxicity.

Medicinal Uses

Analgesic Depurative Haemostatic Resolvent Vermifuge The root stalks are analgesic, antibacterial, anti-inflammatory, antiviral, astringent, febrifuge, haemostatic, vermifuge and vulnerary[238, 279]. A decoction of the dried root is depurative and resolvent[218]. The root contains ‘filicin’, a substance that paralyses tapeworms and other internal parasites and has been used as a worm expellent for humans and also in veterinary medicine[218, 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 also taken internally in the treatment of internal haemorrhage, uterine bleeding, mumps and feverish illnesses[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. Externally, the root is used in the treatment of abscesses, boils, carbuncles and sores[238].

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.