Interrupted Fern
Osmunda claytoniana

Family: Osmundaceae

What it is like

Osmunda claytoniana is a FERN growing to 0.5 m (1ft 8in) by 0.3 m (1ft). See above for USDA hardiness. It is hardy to UK zone 3. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very acid soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil.

Height (m): 0.5

Where it is found

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

E. Asia - China, Japan, Himalayas. Eastern N. America.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 2

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'.

Stem: this often intergrades into leaves.

Medicine

Rating: 1

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

Vermifuge: Expels and kills internal parasites.

Other

Rating:

How it is grown

Likes a soil of swamp mud and loamy or fibrous peat, sand and loam. Succeeds in most moist soils, preferring acid conditions. Requires a constant supply of water, doing well by ponds, streams etc. Plants thrive in full sun so long as there is no shortage of moisture in the soil and also in shady situations beneath shrubs etc. Requires a shady position. Plants are hardy to at least -20°c, they are evergreen in warm winter areas but deciduous elsewhere. Members of this genus are rarely if ever troubled by browsing deer. A very ornamental plant.

Propagating it: 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.

Best place to grow: Woodland Garden Dappled Shade; Shady Edge; Bog Garden;

Habit: Fern

Hardiness: 3-7

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist, wet

Things to keep in mind

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.

Its other names

Local names

Synonyms

O. interrupta.