Blechnum penna Marina

Description

Blechnum penna-marina – alpine water fern

Botanical name: Blechnum penna-marina
Common names: Alpine water fern, little hard fern
Family: Blechnaceae
Plant type: Evergreen fern
Habit: Low, spreading, mat-forming
Pot size: 3 litre pot
Eventual size: Approx. 15–20cm tall × spreading indefinitely by rhizomes
Foliage: Narrow, ladder-like fronds, bronze when young maturing to green; evergreen
Flowers: None — ferns reproduce by spores, not flowers
Scent: Not scented
Aspect / light: Partial to full shade
Soil: Moist, humus-rich; acid to neutral; dislikes lime
Hardiness: RHS H5 (hardy, to about −15°C); USDA zones 6–9
Exposure: Sheltered
Native range: Southern hemisphere (South America, New Zealand and Australia)
Toxicity / pet & child safety: Generally considered non-toxic to people and pets

Blechnum penna-marina, alpine water fern, is a low, spreading evergreen with narrow, ladder-like fronds bronzed when young. Forming dense groundcover, it thrives in moist, acidic, shaded soil and woodland edges.

GardenAdvice notes

A low, creeping evergreen fern from the southern hemisphere, alpine water fern spreads by underground rhizomes to form a dense, weed-suppressing carpet of narrow, ladder-like fronds, attractively bronze-tinted when young. It is one of the best ferns for evergreen groundcover in a cool, moist, shaded, acid spot.

Growing & planting

Plant in spring or autumn in moist, humus-rich, acid to neutral soil in partial to full shade — it dislikes lime and drying out. It is ideal as groundcover in woodland borders, at the front of shady beds and around the moist edges of ponds. Work in leaf mould, and space about 25–30cm apart; it spreads to fill in.

Care & maintenance

Low-maintenance. Keep the soil reliably moist, and mulch with leaf mould in autumn. Trim off any tatty fronds in spring. It spreads steadily by rhizomes, so lift and reduce it if it exceeds its space. No feeding is usually needed beyond an annual mulch.

Propagation

• Division: Lift and divide the spreading rhizomes in spring — the easiest method.
• Spores: Can be raised from spores, though division is far quicker.

Pests & diseases

Generally trouble-free. Slugs may graze young fronds, and it browns if it dries out or is exposed to lime or drying winds. Moist, acid, shaded conditions keep it healthy.

Uses in the garden

Excellent as evergreen groundcover in woodland and shady borders, at the front of moist shaded beds, around pond margins and between other shade plants, forming a fine-textured carpet.

Wildlife value

The evergreen carpet provides year-round cover and shelter for small invertebrates.

Toxicity & safety

Alpine water fern is generally regarded as non-toxic to people and pets.

GardenAdvice tip

This little fern is a lovely evergreen groundcover for a moist, shady, lime-free spot, spreading gently to weave a fine-textured carpet studded with bronze new fronds. It won’t tolerate lime or drought, so give it humus-rich, acid soil that stays reliably moist, and it will quietly knit together to fill a difficult shady corner.

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