Dryopteris carthusiana

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Dryopteris carthusiana is a perennial fern native to damp forests across the Holarctic region (much of the northern parts of the world). In the UK it’s often called the narrow buckler-fern, and in North America it’s known as the spinulose woodfern. It is a tetraploid hybrid with two parent species: Dryopteris intermedia and an extinct species once named Dryopteris semicristata.

What it looks like
- It grows in upright clumps with a short rootstock and dark green fronds that are about 30–50 cm long.
- The leaf stalk is about as long as the blade and is light brown with scales.
- The leaf blade is narrow and divided into many small leaflets in a feathery, double-pinnate pattern; the leaflets are narrow and triangular.
- Spore cases (sori) hang on the underside of the leaves in round, kidney-shaped clusters.

How to tell it apart from similar ferns
- It’s easy to confuse with species like D. intermedia, D. campyloptera, and D. expansa.
- A key difference: the innermost leaflet on the bottom side of the bottom pinna is longer than nearby leaflets in D. carthusiana, while it’s shorter or about the same in D. intermedia.

Growth and habitat
- D. carthusiana is sub-evergreen: fronds can survive mild winters but may die back in harsher winters.
- It prefers acidic soil and avoids lime-rich soil and spring areas.
- It tolerates some direct sunlight better than many related ferns and can do well in disturbed sites like logging areas.

Typical habitats include moist forest depressions, nutural and nemoral forests, coastal scrub, rocky cliff faces, ditches, and coniferous or hardwood-spruce swamps.

Special note
- This fern can grow in places with little natural light, sometimes using artificial light (as in Niagara Cave).