Blechnum penna-marina

RHS Plant Profile

alpine water fern

Ferns

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An evergreen fern forming a mat of spreading, simply pinnate, dark green sterile fronds to 15cm in length, with narrower, erect fertile fronds, the young fronds often reddish

Position

Full shade, Partial shade

Soil Types

Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity: 5–10 years
Max Spread: 0.5-1 metres
Max Height: 0.1-0.5 metres

Growing Conditions

Loam Sand

Moisture: Moist but well–drained or Poorly–drained
pH: Acid or Neutral

Position

Full shade Partial shade

Aspect: East–facing or South–facing or West–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H4

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Blechnaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Matforming
Genus: Blechnum are mostly evergreen ferns with erect or creeping rhizomes and simply pinnate, leathery fronds, the fertile ones usually erect, the sterile often spreading
Name Status: Correct
Plant Range: South America, Australia, New Zealand

How to Grow

Cultivation

Easy to grow in most cool, moist, shaded sites. See how to grow ferns for further advice

Propagation

Propagate by sowing spores (may not come true) in mid to late summer or by division in spring

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Patio and container plants
Flower borders and beds
Banks and slopes
Underplanting of roses and shrubs

Pruning

Dead or damaged fronds may be removed as necessary

Pests

Generally pest-free outdoors

Diseases

Generally disease-free outdoors