Dryopteris erythrosora aka Autumn Fern

Dryopteris erythrosora is a perennial fern from eastern Asia. Its native range includes China, Japan, and Taiwan. It grows on wooded hills and mountain slopes. Gardeners call it autumn fern or Japanese shield fern. Copper shield fern is another name for the species. It keeps its leaves in mild climates. Cold winters may cause it to lose some foliage.

The plant forms a clump with arching, vase-like fronds. Most garden accounts place its height around 1.5–2.5 feet [0.46–0.76 metres]. Its spread ranges from 1–3 feet [0.30–0.91 metres]. RHS gives upper size limits near 3.3 feet [1 metre]. Short, creeping rhizomes let the clump spread at a slow pace. Plants may take five to ten years to reach full size. Broad, triangular fronds can reach 2 feet [0.61 metres] long. Their fine divisions give the plant a light texture.

New fronds open in copper, pink, or orange-red shades. They turn a glossy dark green as they age. Each bipinnate frond has two levels of leaf divisions. The small segments have curved teeth along their edges. Tiny scales occur beneath the midvein and leaf stalk branches. Young sori have bright red covers called indusia. Sori are clusters of structures that produce spores. This fern has no flowers or true fruit. Gardeners can raise plants from spores or divide clumps in spring.

Cool, moist sites with some shade suit this fern well. It also grows in deep shade beneath trees or shrubs. Give it soil rich in organic matter and good drainage. Acid soil suits it, though RHS lists other pH levels. It grows in clay, loam, and sand. Keep young plants watered while their roots settle in. Established plants can cope with brief droughts in shade. Sun requires more soil moisture, and drying winds can harm fronds. RHS rates it H4 for UK gardens. US sources give different ranges, from zones 5–8 to 5–11.

Use it in woodland beds, shaded borders, or containers. Groups can form ground cover beneath shrubs and trees. Deer seldom damage it, and rabbits tend to leave it alone. Dead or damaged fronds need only occasional removal. Sources report few serious pests or diseases outdoors. Salt tolerance is poor. NC State warns that it can naturalize and may become invasive. Florida's account does not identify it as invasive.