How To Grow Karl Foerster Grass

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Karl Foerster Grass, botanically called Calamagrostis x acutiflora (ka-la-mo-GROSS-tis, ak-yoo-tih-FLOR-uh), is a hybrid of two plant species – C. epigejos and C. arundinacea, both indigenous to Asia and Europe. 

It is believed a famous German nurseryman – Karl Foerster – found the plant in the Hamburg Botanical Garden in the 1930s. 

The plant grower also mentioned the unique species in his garden book – The Use of Grasses and Ferns in the Garden. 

It is also the first ornamental grass to won the Perennial Plant of the Year Award in 2001.

Owing to the plant’s popularity, the perennial has more than one botanical name; the hybrid cultivar is widely known as:

  • Acutiflora ‘karl foerster’
  • Calamagrostis x acutiflora ‘karl foerster’
  • Calamagrostis acutiflora ‘karl foerster’

A few common names of Karl foerster grass are:

  • Karl foerster feather reed grass
  • Karl foerster
  • Reed grass
  • Feather reed grass

Karl Foerster Grass Care

Size and Growth

Feather reed grass is a fast growing growth rate perennial plant, reaching up to a mature height of 5’ – 6’ feet and a spread of 2’ – 3’ feet. 

With a fast growth habit, the plant produces 2’ – 3’ feet long and shiny green leaf blades along with 5’ feet stems topped with feathery flowers.

The most prominent feature of Karl Foerster is its lean, erect growth. 

The grass stalks tend to grow in a rigid upward direction with large, dense leaves and colorful flowers.

Flowering and Fragrance

The reed grass features feathery plumes with a flower color ranging from light pink to deep purple to golden tan. 

The flower seed heads of the cool season grasses persist in late winter and turn from golden to tan. 

The early bloomers keep changing their color throughout the season.

The flower stems usually grow up to 5’ feet tall, in early or late spring or early summer, and bear rough flower spikes. 

The bloom time of these lovely flowers is from early spring to late summer.

The flowering species does not evoke any prominent fragrance.

Light and Temperature

Karl Foerster prefers full sun to partial shade for the proper development of showy, green foliage. 

The USDA hardiness zone of the hybrid grass is from 5 to 9.  

The plant does well in winter as well and therefore it is often considered a winter interest plant. 

The hardy plant grows happily in cold temperatures of the fall season. 

In spring, make sure to plant the grass at a temperature below 75° degrees (24° C).

Watering and Feeding

Feather reed grass has normal water needs. 

Ideally, the grassy plant should be watered once a month. 

The flowering benefits from 17” – 24” inches of supplemental watering in the summertime and approximately 15” inches of supplemental watering in the winter season.  

In extreme weather conditions, make sure to water the plant more frequently (regularly or weekly).

Organic slow-release fertilizers are the preferred choice for feeding the ornamental grass. 

However, avoid feeding the cool season grasses in hot weather conditions.

Soil and Transplanting

Karl Forester grass thrives in well-moist soil, yet tolerates dry conditions as well. 

Unlike many ornamental varieties, feather reed grass performs equally well in heavy clay soil type.

The winter-hardy plant is usually transplanted in early fall, soon after the hot summer is over. 

Before transplanting, water thoroughly about an hour or so to help soften the ground. 

Cut the foliage for up to 6” inches deep with a sharp spade and transfer the entire clump in a new hole. 

Make sure the depth of the soil should be the same as the previous one. 

Fill the surrounding hole with wet soil and firm it gently with the hands.

Grooming and Maintenance

The reed grass is a low-maintenance plant and requires yearly pruning only. 

Trim the plant in early spring or early fall to stimulate new growth. 

Prune at least 6” inches of the stem from the base of the plant.

Other Ornamental Grasses You May Like:

How to Propagate Calamagrostis Feather Reed Grass

  • Karl Foerster grass is propagated from divisions. 
  • Divide a mature plant into more than two sections, using a spade. 
  • Make sure the clump contains healthy roots. 
  • Dig up a new large hole and place the divisions in the new hole. 
  • Provide an adequate amount of watering to stabilize the root system. 
  • Generally, propagation is done during the fall.

Calamagrostis Feather Reed Grass Pests and Diseases

Generally, karl foerster is pest and diseases free. 

However, watch out for rusts, especially after a long rainy season.

Karl Foerster Uses

Karl Foersters are popular ornamental grasses, highly valued for their vertical accents. 

In cool summer, the tall, slender plums move gently with the slightest breeze. 

Owing to their aesthetic appeal, the ornamental grass has a great landscape value. 

The light, fluffy plant also makes great cut flowers and dried flower bouquets. 

They are also deer-resistant and ideal for mass planting.

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