<em>Calamagrostis</em>: planting, growing and caring for

Description and botany

Calamagrostis are ornamental grasses, perennials, forming clumps of decorative, linear foliage and bearing flowering panicles. They comprise between 260 and 300 species. They are mainly found in temperate regions of the Northern Hemisphere, notably in Europe and Asia, extending to Russia, and also in North America. Several species grow wild in France, such as Calamagrostis arundinacea, Calamagrostis canescens, or Calamagrostis epigejos. The most widely cultivated species are by far Calamagrostis acutiflora, notably cultivar ‘Karl Foerster’.

Calamagrostis, like many grasses, are robust and very hardy. They can withstand at least between −20 and −25 °C, and sometimes lower. These are easy, undemanding, long-lived plants.

Calamagrostis belong to the large family Poaceae, like grasses that form turf, cereals we eat (wheat, oats, etc.), and ornamental grasses in gardens (stipa, pennisetum…). It is a vast family, with more than 11,000 species. These plants are sometimes confused with Cyperaceae (papyrus, Carex…) and Juncaceae (rushes). They can be rather understated (small, little-coloured flowers), with simple linear foliage… yet are of major economic, food, landscape and ecological importance. Poaceae are generally herbaceous plants with linear leaves with parallel veins, bearing very small, reduced flowers organised in spikelets, grouped on panicles (large inflorescences).

Calamagrostis neglecta: botanical plate

Etymologically, name Calamagrostis comes from Greek Calamus, meaning reed, and Agrostis: grass. It is amusing that Calamus (a palm) and Agrostis (a small meadow or short grass meadow grass) are names of two other plants. Species name acutiflora means “acute-flowered”, likely because its panicles are tighter and finer, narrower than in other species. Karl Foerster (1874–1970) was a German gardener, landscaper and writer, who lent his name to the famous cultivar. Calamagrostis brachytricha has several synonyms: it is also called Calamagrostis arundinacea, or Stipa brachytricha.

Calamagrostis are grasses that grow quickly and form erect, open clumps. They have a fairly straight shape with an upright habit, adding volume. They measure between 60 cm and 1.80 m in height (about 50–60 cm wide), most cultivars exceeding 1 m in height. They gain height when in full flower. Stems are unbranched, erect, straight or slightly arching. With its majestic silhouette, Calamagrostis brings verticality and forms a structuring element in a border.

Calamagrostis begin growth fairly early in spring. They are interesting all year round: even when entering dormancy in winter, they remain decorative because they keep a strongly vertical, structuring form. Cut foliage back near ground level at the end of winter, around February, just before plant resumes producing new leaves.

Calamagrostis are cespitose, forming clumps. A few species (such as Calamagrostis epigejos) have running rhizomes, allowing them to spread.

Calamagrostis offer a long flowering period, from early summer to autumn: depending on cultivar, this occurs between June and October. Flowering of Calamagrostis brachytricha is later, appearing in late summer, around August, and remaining decorative until October–November.

Flowers are grouped in light panicles, carried at top of erect stems above foliage. These panicles reach up to 30 cm long and resemble plumes (even more so in Calamagrostis brachytricha!). They are beige, bronze or light brown, sometimes a little purplish. In sunshine they take on beautiful golden or silvery tones. Generally, panicle colour evolves over time, often bronze-pink or slightly purplish at first, then becoming light brown later. In Calamagrostis brachytricha, inflorescences are initially silvery with pink–purple tints, then turn golden in autumn. Panicle tones in Calamagrostis are soft and warm, very natural.

Panicles are made up of numerous spikelets, each bearing a single flower. These flowers are tiny, barely visible. They are bisexual and have three stamens (producing pollen) and two feathery stigmas (receiving pollen).

The Calamagrostis brachytricha, also called feather reed grass, stands out for its truly feathery inflorescences, very light, shining in sunlight with superb silvery reflections.

Flowering of Calamagrostis acutiflora ‘Karl Foerster’, Calamagrostis rubescens (photo Thayne Tuason) and Calamagrostis brachytricha (photo Dominicus Johannes Bergsma)

Inflorescences sit above foliage, crowning the clump. They are borne at ends of long vertical stems. Panicles are light and sway in wind, bringing movement to garden and animating it. They also create beautiful effects when catching sunlight, or under dew or frost. They remain decorative in winter, although snow can bend and collapse stems.

Calamagrostis inflorescences can be used in fresh or dried flower arrangements.

As with other grasses, Calamagrostis foliage is linear: very long and thin. Combined with plant height and light, feathery flowering, this makes a very graphic plant. Leaves are narrow, glabrous, glossy and nicely arching. They measure between 40 and 90 cm long.

Leaves are generally mid green, but some species have variegated leaves. For example, cream-striated leaves occur in cultivar ‘Overdam’. Calamagrostis ‘Avalanche’ also offers variegated leaves, marginate with white.

Variegated foliage of Calamagrostis ‘Overdam’ (photo Drew Avery) and green leaves of Calamagrostis acutiflora ‘Karl Foerster’

Calamagrostis take on light brown–yellow tones in autumn, soft warm colours that combine well with autumnal hues of some trees or bushes (Cornus, Nandina, Acer, Parrotia, Liquidambar…) and perennials.

Like other grasses, Calamagrostis produce fruits called caryopses. Seedheads remain decorative in winter.

Main Calamagrostis varieties

Most popular varieties

Our favourite varieties

Calamagrostis acutiflora Karl Foerster - Feather Reed Grass

This variety is a must-have, most widespread in gardens. Very decorative, with large clumps of green foliage turning golden in autumn, topped with panicles of light brown–bronze. It is also very hardy and easy to grow!

• Flowering time July to October
• Height at maturity 1,60 m

See the product sheet

Calamagrostis brachytricha - Feather Reed Grass

A species notable for its truly feathery, light flowering, becoming bright and silvery in sunlight, hence its nickname 'Diamond grass'. The inflorescences resemble very soft, airy plumes.

• Flowering time September to November
• Height at maturity 1 m

See the product sheet

Calamagrostis acutiflora Overdam - Feather Reed Grass

This calamagrostis has the particularity of offering variegated foliage of cream-white to yellow, making it brighter than other varieties. It also bears light, silvery panicles, slightly purplish.

• Flowering time July to October
• Height at maturity 1,20 m

See the product sheet

Calamagrostis acutiflora Avalanche - Feather Reed Grass

This variety offers graphic, distinctive foliage, green, marginate with white, topped from early summer by brown-purple flower spikes, later becoming blond. It prefers moist, well-draining soils.

• Flowering time July to October
• Height at maturity 1,20 m

See the product sheet

Calamagrostis acutiflora Waldenbuch - Feather Reed Grass

This is a fairly compact variety, suitable for small gardens. It forms clumps of fine, supple green leaves, turning yellow towards the end of the year. From June it also produces light panicles in light brown or bronze.

• Flowering time July to October
• Height at maturity 90 cm

See the product sheet

Planting

Where to plant?

Plant Calamagrostis preferably in full sun, optionally in partial shade (for example if you live around the Mediterranean). Calamagrostis brachytricha tolerates shade better than other species. However, in general, when Calamagrostis are in sun, their flowering is more generous and their habit more compact, dense and impressive than when they are in shade.

Ideally, Calamagrostis prefer humus-bearing, deep, cool or moist soils, but they are nonetheless undemanding plants that have the advantage of being able to grow almost anywhere: they tolerate clayey, heavy ground but also adapt to dry, poor soils. Calamagrostis brachytricha and epigejos, however, need cooler soil than other species. If substrate tends to dry quickly, plan to water them from time to time. You can also place these species near a pond.

Calamagrostis can be planted as a solitary specimen (for example on a short grass meadow), or in small groups of three to five clumps to bring some structure and volume to a garden. You can even install it in a large group to create a border or hedge, or to obtain a homogeneous, airy backdrop for a bed. As it is a fairly tall plant that remains decorative throughout the year, you can use it to hide a fence, low wall or barrier. Although it prefers to be planted in open ground, it is possible to grow Calamagrostis in a large pot or planter.

When to plant?

We recommend planting Calamagrostis in spring. However, it is also possible to plant at another time of year; most important is to avoid periods of frost or extreme heat.

How to plant?

We recommend a planting distance of about 60 cm, or a little less if you grow varieties smaller than ‘Karl Foerster’ (such as Calamagrostis ‘Waldenbuch’).

1. Place rootball in a basin filled with water. This allows it to rehydrate.
2. Dig a planting hole that ideally should be two to three times the size of the rootball.
3. Remove the rootball from its pot, loosen the roots slightly, then place it in the planting hole. Top of rootball should be level with soil surface.
4. Replace soil around and firm with the flat of your hand.
5. Water generously.

You can also plant Calamagrostis in a large pot or planter. Install a drainage layer at the bottom (gravel, clay pebbles, broken pot shards…), add a light, free-draining potting mix (for example potting compost mixed with a little sand) and place the plant. Water.

We recommend continuing to water regularly during the first weeks while the plant establishes. Afterwards, it will tolerate drought fairly well.

Discover also our advice sheet on planting grasses.

Care

Calamagrostis tolerate dry soils fairly well and do not need much watering. You can water only during weeks following planting, then possibly during dry spells. However, if grown in pot or container, watering will need to be more regular. Likewise, Calamagrostis brachytricha and Calamagrostis epigejos will need slightly fresher soil than others and will therefore require more frequent watering. You can use mulch to help retain soil freshness.

Calamagrostis remain decorative in autumn and winter, but must be pruned at end of winter (February–March), just before they resume growth. Prune hard by cutting clump to 10 cm above soil.

You can also carry out a light tidy-up in autumn, removing damaged stems or leaves.

If growing calamagrostis in pot or container, remember to repot from time to time, preferably in early spring.

Feel free to cut inflorescences to use in bouquets or to make fresh or dried flower arrangements.

Like most grasses, calamagrostis is not susceptible to diseases or pests. In all respects (hardiness, soil, diseases, maintenance…), it is a resilient plant that rarely presents cultivation problems.

Propagation

Like most grasses, Calamagrostis spreads by division of clumps.

Division of clumps

Division is carried out in early spring, when plant is just starting to resume growth.

1. Lift a clump by digging wide enough and gently lifting it from soil so as not to damage roots.
2. Divide it into several pieces. Ensure each has roots. Preferably use pieces taken from the outer edge of the clump.
3. Prepare ground and replant each new clump.
4. Water generously afterwards to encourage their establishment.

Monitor new clumps and continue watering them in following weeks.

If fragments taken are small, they may take two years to flower.

See also our video tips on dividing grasses:

Combining Calamagrostis in the garden

Calamagrostis fit very easily into naturalistic gardens. Use them to create a wild-style garden with an untidy appearance, teeming with life. Create a superb scene by combining Calamagrostis ‘Karl Foerster’ with Verbena bonariensis and Echinacea purpurea. Also make use of the flower spikes of persicarias or knotweeds! Design a wild meadow with many herbs, grasses, punctate with small colourful flowers (scabious, mallows, poppies, poppies, Dierama…). Also discover Salvia nemorosa ‘Caradonna’, with violet flower spikes. You can also create a very natural area near a pond, notably for Calamagrostis brachytricha, which likes fresh soils.

An idea for a natural scene combination: Calamagrostis ‘Karl Foerster’, Echinacea purpurea and Verbena bonariensis (photo GWI – Jenny Lilly – MAP)

With their upright, airy appearance, les calamagrostis also allow creation of a graphic, modern garden. These large grasses will help structure a border. They form tall, upright clumps, adding verticality; use them to play with textures and shapes. Plant a few clumps of Calamagrostis alongside lower plants such as Alchemilla, heucheras, Ajuga reptans, hardy geraniums, bergenias, carex… Calamagrostis is ideal for lightening a somewhat flat border and restoring volume. Scatter a few clumps among other structural plants such as Eremurus, Agapanthus and Veronicastrum.

Calamagrostis softens more rigid forms and strict lines.

You can also use Calamagrostis to design a very light border, with other feathery, airy flowerings! Choose, for example, to accompany them with Verbena hastata, Gaura lindheimeri, scabious, Sanguisorba and Perovskia. Enjoy the superb flower spikes of Pennisetum orientale ‘Tall Tails’. Also discover the wispy flowering of Thalictrum delavayi, gypsophila and Dierama.

Create a superb late-season scene, in autumn–winter, with plants in purplish, beige, brown, bronze or orangey tones. Choose, for example, Asters, Dahlias, Echinacea ‘Tangerine Dream’, Sedum ‘Autumn Joy’, evergreen grasses… Favour plants with an open, transparent habit, whose flowers and foliage catch sun rays, frost or raindrops… Plants you can leave in place, whose structure, infrutescences (seedheads) or berries remain decorative in autumn–winter. Choose Echinops, Eryngiums, Dipsacus fullonum, Perovskia, Phlomis… Regarding decorative berries, choose Callicarpa, Symphorines or Euonymus. Also take advantage of foliage and decorative bark, notably with dogwoods, Nandina domestica or Acer palmatum…

A rather natural autumn scene in soft tones, featuring Calamagrostis ‘Karl Foerster’, Miscanthus, Aconitum carmichaelii ‘Arendsii’, kniphofias and Aster ‘Violet Queen’ (photo MAP – Clive Nichols – Pettifers Garden Oxfordshire)

Finally, use calamagrostis to design a low-maintenance garden! They are ideal for planting in parts of garden that are seldom tended, because, apart from pruning them once a year at the end of winter, calamagrostis require very little attention. Create a natural area: ecological, water- and labour-saving. Choose other grasses, plants that tolerate drought, groundcovers, and plants that naturalise, returning each year.