Feather reed grass (Calamagrostis x acutiflora) is a dramatic ornamental grass used in many types of landscapes. Probably the most common culitivar is ‘Karl Foerster’. When the Perennial Plant Association named this as their Plant of the Year 2001 they called it “one of the most versatile, attractive, and low maintenance ornamental grasses.”
This is a cool season grass, hardy in zones 3-9, so the deep green, glossy foliage appears early in the spring. In cold climates the color lasts through late fall or early winter when it turns a golden tan color, but in mild climates the foliage may remain green. The plants grow erect, in a narrow clump 2-3 feet tall and less than 2 feet wide.
In early summer, flowers stems 5-6 feet tall appear. This cultivar blooms a few weeks earlier than common feather reed grass. The heads of the loose, feathery inflorescences emerge green, then open to airy, rosy-pink plumes. After a few weeks the color changes to dark maroon, then to bronze, and finally to golden tan. The plants flower stalks remain upright through the winter to provide winter interest.
C. x acutiflora is reported as a natural hybrid of C. epigejos (native to Europe, Asia and Africa) and C. arundinacea (native to Eurasia, China and India) that occurred in the Hamburg Botanical Garden. It was introduced to the industry as an ornamental in 1950 by German nurseryman Karl Foerster. It was brought into the United States from Denmark in 1964. It is almost identical to C. x acutiflora ‘Stricta’ (so identical that these plants are often confused by some nurseries) but ‘Karl Foerster’ does not self seed.
C. x acutiflora ‘Karl Foerster’ is excellent as a specimen plant, providing a vertical accent in the landscape or as a massed planting. The slightest breeze sets this grass in motion and the graceful movement is a highlight for any landscape. In heavy rain or wind, the stems may flop in all directions but quickly return to vertical when dried off.
Put it in a spot where the afternoon sun will shine on the seedheads, making them appear almost golden in color, for a dramatic effect. It is also useful in patio pot containers, as a backdrop fro roses or as a seasonal hedge or screen. ‘Karl Foerster’ feather reed grass combines well with other perennials, especially late summer and fall-blooming perennials such as Coreopsis, Echinacea, Liatris, and Rudbeckia.
This grass is also good for use in fresh or dried arrangements. Stems cut before the flowers mature will last for months in an arrangement, maintaining the golden tan color.
This long-lived perennial grass grows best in full sun to partial shade and prefers well-drained, fertile soils with sufficient moisture but is somewhat drought tolerant once established. Unlike many of the other ornamental grasses it does well in heavier clay soils. Fertilization may be required to produce maximum height in infertile soils. It has no serious disease or insect problems and is not favored by deer. It may flop over if grown in shade.
Little maintenance is required except to cut back the stems to about 6 inches annually. Since this plant starts it’s growth early in spring, the previous year’s growth needs to be cut back in late winter or very early spring to avoid damaging the new growth.
This grass is best propagated by division in the fall or spring. Large clump division may be done in the fall with a good show of flowers the following spring. Smaller clumps will require a second growing season to fully develop a mature flowering effect. This cultivar is sterile so there will never be seedlings in the garden.
– Susan Mahr, University of Wisconsin – Madison