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How to Grow Blechnum

Hard fern, Blechnum spicant
Hard fern, Blechnum spicant

Blechnum is a woodland fern with leathery, usually once-pinnate or deeply lobed, ladder-like fronds. Blechnum is sometimes known as hard fern or deer fern.

Blechnum is a genus of 150 to 200 species of usually evergreen, rhizomatous, terrestrial ferns found mostly in moist, sheltered, acidic soils in temperate or tropical regions.

Grow Blechnum in a shady border or woodland garden. Blechnum can be grown indoors in regions where it is not hardy.

Get to Know Blechnum

  • Plant Type: Fern
  • Growing Zones And Range: Zones 8-11
  • Hardiness: Hardy to Zone 8
  • Height And Width: 9 inches (22cm) to 6 feet (1.8m) tall and 9 inches to 3 feet (1m) wide depending on the variety
  • Foliage: Pinnate usually leathery fronds
  • Uses: Grow in woodland, in shady herbaceous border, or in rock garden
  • Common Name: Hard fern, deer fern
  • Botanical Name: Blechnum
  • Family Name: Blechnaceae
  • Origin: Temperate and tropical regions worldwide
Hard Fern - Blechnum spicant
Hard Fern – Blechnum spicant

Where to Plant Blechnum

  • Light outdoors: Grow Blechnum in deep shade outdoors.
  • Soil outdoors: Grow in moist, humus-rich, acidic soil.
  • Light indoors: Provide bright filtered or indirect light.
  • Soil indoors: Grow Blechnum indoors in a mix of 1 part each acidic loam, medium-grade bark, and charcoal; 2 parts sharp sand; and 3 parts coarse leaf mold.
  • Where not hardy, grow Blechnum in a greenhouse or conservatory.

When to Plant Blechnum

  • Set Blechnum outdoors after all danger of frost is past.

Planting and Spacing Blechnum

  • Space Blechnum 9 inches to 3 feet (1m) apart depending on the variety.

How to Water and Feed Blechnum

  • Water Blechnum freely to keep the soil evenly moist during the growth period; water moderately in winter.
  • Fertilize Blechnum with an organic fertilizer formulated for ferns.

Blechnum Care

  • Frond discolor if air circulation is poor, and in a dry atmosphere.
  • Blechnum fronds may scorch in full sun.

Growing Blechnum as a Houseplant

  • Grow Blechnum indoors in a mix of 1 part each acidic loam, medium-grade bark, and charcoal; 2 parts sharp sand; and 3 parts coarse leaf mold.
  • Provide bright filtered light indoor and moderate to high humidity and good ventilation.

Blechnum Pests and Diseases

  • Blechum is prone to leaf spot and rust.
  • Scaled insects, mealybugs, and caterpillar can be a problem.

Blechnum Propagation

  • Sow spores in late summer.
  • Divide in spring; divisions can take time to re-establish.

Blechnum Varieties to Grow

  • Blechnum alpinum, see B. pennamarina.
  • B. appendiculatum. Slightly arching; lance-shaped pinnate dark green fronds; grows to 15 inches tall; Zone 10-11.
  • B. australe. Slightly arching fern; linnear pinnate midgreen fronds; grows to 15 inches tall; Zones 10-11.
  • B. brasiliense. Evergreen, upright, trunk-like rhizones; oblong-lance-shaped pinnate mid to dark green fronds; grows 3 to 5 feet; Zone 11.
  • B. chilense. Evergreen, creeping rhizomes; ovate to lance-shaped pinnate, dark green fronds; grows 3 to 6 feet; Zone 10-11.
  • B. gibbum. Evergreen with upright trunk-like rhizome; black-scaled, bright green fronds grows to 3 feet tall and wide; Zones 12-15.
  • B, nudum. Evergreen, ovate-lance-shaped fronds; grows to 3 feet tall and wide; Zones 8-10.
  • B. occidentale, hammock fern. Evergreen with erect or ascending rhizomes; lance-shaped, mid-green fronds, grows 9 to 18 inches tall and wide; Zones 9-11.
  • B. penna-marina, syn. B. alpinum. Evergren with linear, pinnate fronds, grow 4 to 8 inches tall and wide; Zones 10-15.
  • B. spicant, deer fern. Evergrene with creeping rhizoes; narrow lance-shaped , pinnate, dark green fronds; grows 8 to 10 inches tall and 24 inches wide; cultivars include ‘Crispum’, ‘Cristatum’, and ‘Richard’s Serrate’; Zones 10-11.
  • B. wattsii. Arching, braodly ovate pinnate dark green blades with bronzy red new growth; grows to 12 inches tall; Zones 9-11.

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