Grasses have always been an integral part of nearly every nature scene – fields, roadsides, sand dunes, even the shadowy depths of woodlands. But grasses are just now experiencing a rise in popularity as gardeners discover the striking array of textures, forms, sizes and colors they offer. The multi-season interest of ornamental grasses is unsurpassed, and their luminous quality and fluttering response to even the slightest breeze only adds to their appeal.
Calamagrostis acutiflora ‘Karl Foerster’ is one ornamental grass reaping the benefits of this new-found fame. Recently named Perennial Plant of 2001 by the Perennial Plant Association, Karl Foerster is a versatile and maintenance-free ornamental commonly known as feather reed grass.
Named by German plant breeder, Karl Foerster, the variety is native to moist woodlands and alpine meadows. Suitable for mass plantings or containers, Karl Foerster tolerates full sun or partial shade.
The grass has deep green upright foliage that appears in early spring and matures to four feet in height with a 20-inch base. Foliage and blooms are soft to the touch and resemble wheat with its fluffy flower plumes.
Blooms first appear on 6 foot plumes in late spring (May through June). Green foliage gives way to slightly purplish, loosely feathered plumes that change to gold late in the season. Inflorescences are commonly used for fresh or dried arrangements. In shady conditions (less than six hours of sunlight), blooms may droop, creating an arching effect. In colder climates, blooms appear two to three weeks earlier on more compact clumps; in warmer climates, foliage will be taller with narrow seed heads.
Because Karl Foerster does not produce viable seed, vegetative propagation is necessary. To propagate large numbers (thousands) of seed, cell packs in 50s or 72s should be used. One to two eyes for each division make new roots in one to two weeks. The best time to propagate is early fall (September through October) or very early spring (February through March). Cut root shoots to 1/2 inch for easy plugging. Liners can be potted in late spring into one quart or one gallon containers.
Temperature: Warm greenhouse temperatures ranging from 55° to 75° F are needed for at least eight weeks to establish a healthy root system.
Media: A slow release fertilizer (18-6-12) can be incorporated into the soil with a soluble liquid feed of 20-20-20 one to two times a week for maximum growth. Most grasses will tolerate a wide range of soil types but prefer a pH between 5 and 7. Karl Foerster will tolerate various soil conditions including heavy clay soils. For maximum growth, soil should be porous enough to allow good drainage.
Pruning: Pruning of the foliage isn’t necessary but can be used to increase the plant’s girth at the crown.
Once finished, plants can be placed in the landscape on 2-foot centers for mass plantings or singularly for specimen plantings.
Media: Soil should be richly organic and retain some moisture. Irrigation with fertilizer is essential under poor soil conditions for the first year of establishment.
Transplant: Grass shouldn’t be transplanted during its summer dormancy.
Potential problems: Karl Foerster is the most heat tolerant of the cool season grasses. It will also tolerate dryer conditions. Few pests or diseases plague this variety although foliar rust may discolor the leaves during wet summers.
Growing season: A cool season grass, Karl Foerster’s growth occurs between 40° and 75° F. It has two growing seasons, late winter and late summer. Blooms appear in late spring as daylight and temperature increase. With increased temperatures, 12 or more hours of daylight and a reduction of rainfall, plants enter a summer dormancy.
In late summer, as day length shortens and temperatures decrease, growth resumes. In late fall, freezing temperatures halt growth and winter dormancy begins. Life cycles are repeated again in late winter.
Culture Tips for Feather Reed Grass