Marginal Woodfern, Leather Wood Fern

Dryopteris marginalis

Physical Characteristics

Dryopteris marginalis is an evergreen Fern growing to 0.8 m (2ft 7in) by 0.3 m (1ft) at a medium rate. See above for USDA hardiness. It is hardy to UK zone 4. It is in leaf all year. 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

N. America - Canada to Georgia and westwards to the Rockies.

Habitats

Woodland Garden Dappled Shade; Shady Edge;

Edible Uses

None known

Medicinal Uses

Antirheumatic Odontalgic Vermifuge The root contains ‘filicin’, a substance that paralyses tapeworms and other internal parasites and has been used as a worm expellent[171, 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. An infusion of the root has been used in the treatment of rheumatism[257]. A warm infusion, held in the mouth, has been used to treat toothaches[257].

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.