Crown Wood-Fern
Dryopteris crassirhizoma
Family: Dryopteridaceae
What it is like
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.
Height (m): 1
Where it is found
Mountains all over Japan. A terrestrial fern, growing on the humus-rich floor of temperate forests, often in colonies.
E. Asia - Japan, Korea, Manchuria.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 1
Young fronds. No further details, but we would advise caution. See the notes above on toxicity.
Medicine
Rating: 4
The root stalks are analgesic, antibacterial, anti-inflammatory, antiviral, astringent, febrifuge, haemostatic, vermifuge and vulnerary. A decoction of the dried root is depurative and resolvent. 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. 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 also taken internally in the treatment of internal haemorrhage, uterine bleeding, mumps and feverish illnesses. 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. Externally, the root is used in the treatment of abscesses, boils, carbuncles and sores.
Analgesic: Relieves pain.
Depurative: Eliminates toxins and purifies the system, especially the blood.
Haemostatic: Controls internal bleeding.
Resolvent: Breaks down tumors. This might be placed under antitumor.
Vermifuge: Expels and kills internal parasites.
Other
Rating:
How it is grown
Prefers an acid to neutral soil, succeeding in ordinary fertile soil in a shady position. Prefers a moist soil, but is drought tolerant when well established. Members of this genus are rarely if ever troubled by browsing deer.
Propagating it: 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.
Best place to grow: Woodland Garden Dappled Shade; Shady Edge;
Habit: Fern
Hardiness: 5-9
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade
Moisture: Moist
Things to keep in mind
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.