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How to Grow Chasmanthium — Wild Oats, Sea Oats

Sea Oats
Sea Oats (Chasmanthium latifolium)

Chasmanthium — commonly called wild oats, wood oats, or bamboo grass — is an ornamental clump-forming grass. Its broad, bamboo-like leaves are topped by arching flowering stems. The flowers are silvery green spikelets that resemble flattened clusters of oats.

Chasmanthium is a good choice for growing in a mixed or herbaceous border or in a woodland garden. The flowering stems dry to attractive greenish straw color and look good in dried arrangements.

Chasmanthium clumps broaden slowly and are not aggressive like bamboo, but the plants will self-sow and can become invasive when seeds are not cleared after they fall.

Chasmanthium is a genus of six species of perennial grasses, mostly from woodland eastern and central United States, Mexico, and Central America.

Sea Oats, Chasmanthium
Sea Oats, Chasmanthium

Get to Know Chasmanthium 

  • Plant type: Perennial 
  • Growing zones and range: Zones 4 to 8 
  • Hardiness: Hardy to Zone 4
  • Height and width: 30 inches to 48 inches in bloom x 18 inches (76.2cm to 122cm in bloom x 46.7cm)  
  • Growth rate: Slow 
  • Form and habit: Clump-forming grass 
  • Foliage: Linear to narrowly lance-shaped leaves that turn brown in winter 
  • Flowers: Arching flower stems, 2-5 feet (.6-1.5m) tall, carrying showers of silvery green flower spikelets that resemble flattened clusters of oats (or flattened armadillos); flowering stems dry to an attractive greenish straw color and look good in dried arrangements 
  • Bloom time: Summer
  • Uses: One of the best grasses for partial shade; flowers are lovely in dried arrangements, or as a focal point, ground cover, or herbaceous or mixed border 
  • Garden companions:  
  • Common name: Wild oats, sea oats, bamboo grass
  • Botanical name: Chasmanthium 
  • Family name: Poaceae 
  • Origin: North and Central America 

Where to Plant Chasmanthium 

  • Plant Chasmanthium in partial shade; plants will grow in full sun. 
  • Plant Chasmanthium in rich, moist, well-drained soil; plants will tolerate dry soil. 

When to Plant Chasmanthium 

  • Sow Chasmanthium seed in containers in a cold frame in spring.
Chasmanthium latifolium
Chasmanthium latifolium

Planting and Spacing Chasmanthium 

  • Space Chasmanthium 24 inches (61cm) apart.  

How to Water and Feed Chasmanthium 

  • Give Chasmanthium regular water. 
  • Feed Chasmanthium with an all-purpose organic fertilizer in spring. 

How to Care for Chasmanthium 

  • Cut Chasmanthium down to the ground in late winter to very early spring. 
  • Since Chasmanthium self-sow with enthusiasm, cut them back in fall before seed heads shatter to curtail this tendency.  
  • Stake Chasmanthium if flowering stems sprawl too far.  

Chasmanthium Pests and Diseases 

  • Pests and diseases are infrequent.

Chasmanthium Propagation 

  • Propagate Chasmanthium by dividing clumps in spring or early summer, sow seeds, or pot up self-sown seedlings.  
  • Divide Chasmanthium clumps when they become overgrown and flowering diminishes. 

Chasmanthium Varieties to Grow 

  • C. latifolium (formerly Uniola latifolia), Northern Sea Oats, native North American warm-season grass forming 2-3 foot (.6-.9m) tall, 2 foot (.6m) wide clumps. Has bamboolike leaves 4-10 inches (10-25cm) long, that turn yellow in winter, and showy, drooping green seed heads in midsummer that ripen to light brown. To 3 feet (1m) tall and 24 inches (60cm) wide. Zones 5 to 9.  

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