Calamagrostis

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Found in Europe, Northern Asia, and Central and North America, the genus Calamagrostis includes roughly 250 species. They grow in a range of habitats, such as low-density forests, fields, and the edges of lakes and streams. Many individual species withstand a wide range of conditions, from wet to average and sun to shade. Calamagrostis holds one of the most widely used and valued ornamental grasses, C. x acutiflora ‘Karl Foerster’.

DIGGING DEEPER

Calamagrostis comes from the Greek kalamos (reed) and agrostis (a kind of grass), hence the common name “reed grass.”

Other grasses share the common name of “reed” grass. For example, Arundo donax is called Giant Reed and is used for making reeds in musical instruments, Phalaris arundinacea, known as Reed Canary Grass, is a marsh plant that spreads by rhizomes. Grasses within Calamagrostis are sometimes referred to as “small reed.”

The most famous member of Calamagrostis is C. x acutiflora ‘Karl Foerster’. When it was discovered in the Hamburg Botanical Garden in the 1930s, this lovely grass was believed to be a variation of C. epigejos (C. epigejos ‘Hortorum’).

German plantsman Karl Foerster (1874-1970) was not convinced. His studies concluded it was a naturally occurring hybrid of C. epigejos and C. arundinacea. For a short time it was known as C. x acutiflora ‘Stricta’. However, because Latinized cultivar names are considered unacceptable in botanic nomenclature, it was rechristened C. x acutiflora ‘Karl Foerster’.

Introduced to the U.S. in 1964, ‘Karl Foerster’ is now one of the most popular grasses in the nursery trade. It is the first grass to receive the Perennial Plant of the Year Award® (2001), which awards plants for their good looks, long-lasting beauty, and undemanding growing requirements. From ‘Karl Foerster’ came colorful variations, such as white-green variegated C. x acutiflora  ‘Avalanche’ and  ‘Overdam’, and the gold-green variegated ‘Eldorado’. All these selections are cool season grasses, blooming in spring and slowing their growth as temperatures climb in early summer.   

Karl Foerster’s legacy lives on in the Foerster Stauden Perennial Garden in Potsdam, Germany. These grounds have been awarded landmark status and act as a memorial to this gifted horticulturalist.

Other Calamagrostis

Winner of the Royal Horticultural Society's Award of Garden Merit (RHS AGM) in 2006, Calamagrostis brachytricha forms graceful clumps of green foliage, which are graced with airy pink-tinged flowers. Under preferred conditions, these blooms are numerous and highly ornamental. Blooms arrive mid-late summer and persist into fall. Called Korean Feather Reed Grass, it is one of the few commercially available grasses that can bloom and do well in partial shade. And unlike the other better-known Calamagrostis, Korean Feather Reed Grass is a warm season grass.

Of the more than twenty Calamagrostis species found in North America, Canada Bluejoint (C. canadensis) is the most widespread. It’s found from the subarctic lands of Alaska and Quebec throughout most of the U.S. It stops short of the southernmost states. It’s a versatile plant. According to the U.S. Forest Service, Canada Bluejoint occurs as an understory plant in riparian and cool, moist forest communities.  It’s a long-lived, sod-forming grass that helps provide stream bank stability and recovers rapidly after oil spills. This adaptability makes C. canadensis a noteworthy candidate for green infrastructure projects.

Genus Debate

Calamagrostis, Agrostis, and Deyeuxia share many characteristics, and the differences among them are often subtle. This makes classifying species into these genera difficult. When interspecific hybridization and asexual reproduction occur naturally, the task is even harder. According to the Flora of North America, Calamagrostis is sometimes confused with Agrostis. However, there is no one single character that distinguishes all species of Calamagrostis from those of Agrostis. To add to the confusion, using the criteria proposed by some taxnomists to distinguish between Calamagrostis and Deyeuxia would put most North American species of Calamagrostis into Deyeuxia. Additional study and extensive DNA testing are needed to shed more light on the subject.