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How to Grow Osmunda – Cinnamon Fern, Royal Fern

Osmunda japonica
Osmunda japonica

Osmunda genus includes the ferns commonly called cinnamon fern and royal fern. Osmunda is a genus of imposing ferns. All are large, coarse, deciduous ferns.

Osmunda has broadly lance-shaped to triangular-ovate pinnate fronds. The fronds arise from large erect rhizomes. Fronds turn yellow or golden brown in autumn. Fertile fronds produce clusters of spherical greenish sporangia which turn rust-brown or blackish.

Grow Osmunda in damp borders or at the margins of a pond or stream. Osmunda is a striking focal point near a waterside.

Osmunda rhizomes have a heavy growth of matted brown roots–these fibrous roots are used for potting orchids.

Osmunda is a genus of 12 species of deciduous ferns ground in damp places in all continents except Australasia.

Osmunda regalis, or royal fern, blooming in spring
Osmunda regalis, or royal fern, blooming in spring

Get to Know Osmunda 

  • Plant type: Ferns 
  • Growing zones and range: Zones 2 to 10 
  • Hardiness: Hardy to Zone 2
  • Height and width: Cinnamon ferns can grow 2 to 5 feet (0.6-1.5m) tall; royal fern can grow to 6 feet (2m) tall and 12 feet (4m) wide.
  • Growth rate: =Moderate
  • Form and habit: Erect fronds  
  • Foliage: Broadly lance-shaped to triangular-ovate or ovate, pinnate, 2-pinnate, or 2-pinnatifid sterile fronds arise from large, erect rhizomes and turn yellow or golden brown in autumn; distinctive, partially or wholly fertile fronds produce branched clusters of spherical greenish sporangia, which turn rust-brown or blackish on reduced pinnae; the fiddleheads and leaf stalks are densely covered with hair 
  • Fruits: Spores are produced either on separate, specialized, often cinnamon-colored or brown fronds; spore-bearing parts lack leafy tissue altogether 
  • Uses: Damp border, margins of a pond or stream, striking focal point near a waterside, naturalistic plantings 
  • Common name: Flowering fern 
  • Botanical name: Osmunda 
  • Family name: Osmundaceae 
  • Origin: In damp places on all continents, except Australasia 

Where to Plant Osmunda 

  • Plant Osmunda in light, dappled shade, although many are perfectly sited in full sun.  
  • Plant Osmunda in moist, fertile, humus-rich, preferably acidic soil. 

When to Plant Osmunda 

  • Sow Osmunda spores at 59-61°F (15-16°C) within 3 days of ripening in summer; they lose viability quickly.
  • Set container grown Osmunda in the garden in spring or autumn.

Planting and Spacing Osmunda 

  • Plant Osmunda 2 feet (.6m) apart.  
Osmunda
Osmunda

How to Water and Feed Osmunda 

  • Keep soil around Osmunda damp to wet. 
  • Feed Osmunda with an all-purpose organic fertilizer in spring. 

How to Care for Osmunda 

  • Osmunda grows best when the ground is kept damp.

Osmunda Pests and Diseases 

  • Osmunda are prone to rust.  

Osmunda Propagation 

  • Divide Osmunda clumps from established colonies in autumn or early spring.  

Osmunda Varieties to Grow 

  • Osmunda cinnamomea, Cinnamon fern, deciduous fern bearing shuttlecocks of ovate-lance-shaped, pinnate, pale green sterile fronds, 2-5 feet (.6-1.5m) long, with pinnatifid segments, surrounding much narrower, erect fertile fronds, to 3 feet (1m) long. The top of each fertile frond is a mass of cinnamon-brown sporangia in spring. To 36 inches (90cm) tall and 24 inches (60cm) wide. East North America. Zones 2 to 10. 
  • O. claytoniana, Interrupted fern, deciduous fern bearing shuttlecocks of ovate-lance-shaped, pinnate, pale green sterile fronds, to 36 inches (90cm) long, with pinnatifid segments; they surround taller fertile fronds, similar but with some of the middle pinnae reduced and, in late spring, covered in sporangia, which are initially blackish, later yellow-green, then rust-brown. To 36 inches (90cm) tall and 24 inches (60cm) wide. East North America. Zones 2 to 10.  
  • O. regalis, Flowering fern, Royal fern, deciduous fern producing dense clumps of broadly triangular-ovate, 2-pinnate, bright green sterile fronds, 3 feet (1m) or more long. In summer, partially fertile fronds, to 6 feet (2m) long, have tassel-like tips, with brown or rust-colored sporangia, covering the much smaller pinnae. The fibrous rootstock is the source of osmunda fiber, used as a potting mix for orchids. To 6 feet (2m) tall and 12 feet (4m) wide. Temperate and subtropical regions. Zones 2 to 10.  

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