Karl Foerster Grass, botanically called Calamagrostis x acutiflora ‘Karl Foerster’ (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 win 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’
The common names of Karl Foerster grass are the following:
- Karl foerster feather reed grass
- Karl foerster
- Reed grass
- Feather reed grass
In this article, we’ll share everything you need to know about proper Karl Foerster feather reed grass care.
Karl Foerster Grass Care
How to plant Karl Foerster grass correctly is essential for its successful growth. Here are the tips to take into account:
Karl Foerster Grass Height, Size, and Growth
So, how fast does karl foerster grass grow?
Karl foerster grass growth rate is fast-growing, reaching 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, shiny, arching green leaves and 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.
Moreover, does Karl Foerster grass spread is a common question among gardeners considering planting this grass.
While it may spread slightly over time through rhizomes, it is not considered invasive and does not self-seed. After seven to 10 years, you may need to divide the grass to control its expansion.
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 feathery flower spikes usually grow upright 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 also does well in winter, so it is often considered a winter interest plant.
The hardy plant grows happily in cold temperatures during the fall season.
In spring, make sure to plant the grass at a temperature below 75° degrees (24° C).
Watering and Fertilizer
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 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 also tolerates dry conditions.
Unlike many ornamental varieties, feather reed grass performs equally well in heavy clay soil types.
The winter-hardy plant is usually transplanted in early fall, soon after the hot summer is over.
When to plant Karl Foerster grass is an important consideration for the successful growth and establishment of this grass.
Before transplanting, water thoroughly for about an hour or so to help soften the ground.
Cut the foliage up to 6” inches deep with a sharp spade and transfer the entire clump into 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 your hands.
In addition, ensure to add a layer of organic mulch around the plant to maintain soil moisture.
Grooming and Maintenance
When to trim Karl Foerster grass is an important maintenance consideration for its health and appearance.
So when to cut back karl foerster grass?
The reed grass is a low-maintenance plant and requires yearly pruning only.
With pruning shears, 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:
- Maiden Grass – Miscanthus sinensis gracimillus
- Purple Fountain Grass – Pennisetum setaceum “Rubrum”
- Pampas Grass care – Cortaderia selloana
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 or shovel.
- 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
You might ask, what are some karl foerster grass problems?
Fortunately, Karl Foerster is pest and disease-free. However, watch out for rust, 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 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 and specimen plantings.