Herb: Interrupted Fern

Latin name: Osmunda claytoniana

Synonyms: Osmunda claytonia, Osmunda interrupta

Family: Osmundaceae

Medicinal use of Interrupted Fern:

The roots are used as an adulterant for Dryopteris felix-mas in the treatment of internal worms.

Description of the plant:


50 cm
(1 foot)

Habitat of the herb:

Wet places in C. Japan. Open slopes, rarely in forests, 2800 - 3300 metres in Kashmir.

Edible parts of Interrupted Fern:

The young fronds are eaten. Cooked as a vegetable. The centre of the clump, below ground level, is the source of a small edible pith called "fern butter".

Propagation of the herb:

Spores - they very quickly lose their viability (within 3 days) and are best sown as soon as they are ripe on the surface of a humus-rich sterilized soil in a lightly shaded place in a greenhouse. Keep the compost moist, preferably by putting a plastic bag over the pot. Plants develop very rapidly, pot on small clumps of plantlets as soon as they are large enough to handle and keep humid until they are well established. Do not plant outside until the ferns are at least 2 years old. Cultivars usually come true to type. Division of the rootstock in the dormant season. This is a very strenuous exercise due to the mass of wiry roots.

Cultivation of Interrupted Fern:

Wet places in C. Japan. Open slopes, rarely in forests, 2800 - 3300 metres in Kashmir.

Known hazards of Osmunda claytoniana:

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

Plant information taken from the Plants For A Future.