Dryopteris crassirhizoma aka Shield Fern

Dryopteris crassirhizoma is a perennial fern from temperate eastern Asia. Its names include thick-stemmed wood fern and crown wood fern. Its range covers parts of China and the Russian Far East. It also grows in Korea, Japan, and Taiwan. In Japan, it grows in mountain forests across the country. It lives on forest floors rich in humus, sometimes forming colonies. This woodland setting gives context for its shade needs in gardens.

The plant forms a vase-shaped clump with an upright outline. Garden plants reach about 3–3.3 feet [0.9–1 metre] tall and wide. A thick brown crown holds the upright and gently arching fronds. Each frond has narrow, lance-shaped pinnae with lobed edges. The RHS classes its leaves as semi-evergreen. Chicago Botanic Garden notes that the leaves stay through winter. They fall flat over the crown and roots during cold weather. This fern does not flower, so it has no bloom season.

Choose a cool, moist site with light or deep shade. Moist, well-mulched soil suits it well. The RHS lists chalk, clay, loam, and sand as suitable soils. It also accepts acid, neutral, and alkaline conditions. It can grow in sun when it gets plenty of moisture. It tolerates dry shade, but new plants need regular watering. Mulch helps during the first growing season. The RHS accepts both moist, drained soil and poorly drained soil. It rates this fern H6 for UK winter hardiness. Other sources list USDA zones 5–8. Plants take about five to ten years to reach full size.

Its clear shape suits woodland gardens and shaded beds. It can serve as a focal plant or ground cover. It also fits borders and planting beneath roses or shrubs. The RHS includes it in courtyard and informal garden schemes. Deer resistance adds value where browsing causes trouble. Missouri Botanical Garden also lists resistance to rabbits and deep shade. Care needs are low, with no serious pest or disease issues reported. Remove dead or damaged fronds when needed. Chicago recommends cutting old fronds back in spring for fresh growth. Divide plants in spring to make new plants.

Plants For A Future lists young fronds as an edible part. Its low food rating comes with a clear warning. Fresh tissue contains thiaminase, which can reduce available B vitamins. Large amounts may cause serious harm. Heat or thorough drying destroys this enzyme. That does not establish that the fern is safe to eat. The same source records medicinal uses of the root stalks. These include pain relief, wound care, and treatment of internal worms. It links the worm treatment to a compound called filicin. These are reported uses, not evidence for safe home treatment.