<em>Calamagrostis</em>: planting, growing and care

Description and botany

Calamagrostis are perennial ornamental grasses that form clumps of decorative, linear foliage and bear panicles. There are between 260 and 300 species. They are mainly found in temperate regions of Northern Hemisphere, notably in Europe and Asia up to Russia, but 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 variety ‘Karl Foerster’.

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

Calamagrostis belongs to large family Poaceae, like grasses that make up lawn, cereals we eat (wheat, oats, etc.), or ornamental grasses in gardens (Stipa, Pennisetum…). It is a huge family, with over 11,000 species. These plants are sometimes confused with Cyperaceae (papyrus, Carex…) and Juncaceae (rushes). They can be quite discreet (small, rather uncoloured flowers), with simple linear foliage… yet of great 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, gathered 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 reed-like plant) and Agrostis (small meadow grass) are names of other plants. Species name acutiflora means “acute-flowered”, probably because its panicles are tighter and finer, narrower than in other species. Karl Foerster (1874–1970) was a German gardener, landscape designer and writer, who lent his name to the famous variety. Calamagrostis brachytricha has several synonyms: it is also called Calamagrostis arundinacea or Stipa brachytricha.

Calamagrostis are grasses that grow quickly and form upright, ample clumps. They have a fairly straight shape, a vertical habit that adds volume. They reach between 60 cm and 1.80 m in height (with 50–60 cm spread), most varieties exceeding 1 m. They gain height when in full flowering. Stems are unbranched, erect, straight or slightly arching. With its majestic silhouette, Calamagrostis brings verticality and provides a structuring element in a border.

Calamagrostis begin growth fairly early in spring. They are interesting year-round: even when entering dormancy in winter, they remain decorative, keeping a vertical, structuring form. Wait until late winter, around February, to cut foliage back close to ground, just before plant starts producing new leaves.

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

Calamagrostis offer a long flowering period, from early summer to autumn: depending on variety, flowering 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 gathered in airy panicles, borne at top of erect stems above foliage. These panicles measure up to 30 cm long and resemble plumes (even more so in Calamagrostis brachytricha!). They are beige, bronze or light brown, sometimes slightly purplish. In sun they take on beautiful golden or silvery tones. Generally, panicle colour evolves with time, starting bronze-pink, slightly purplish, then becoming light brown. In Calamagrostis brachytricha, inflorescences are first silvery with pink–purple tints, then turn golden in autumn. Panicle hues are soft, warm and very natural.

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

The Calamagrostis brachytricha, also called feather reed grass, stands out for its very feathery, lightweight inflorescences that shine in sunlight, taking on superb silvery reflections.

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

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

Calamagrostis inflorescences can be used successfully in bouquets of fresh or dried flowers.

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

Leaves are generally medium green, but some species have variegated leaves. For example, ‘Overdam’ has leaves streaked with cream, and Calamagrostis ‘Avalanche’ also offers variegated leaves, margined 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 sit 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 varieties of Calamagrostis

Most popular varieties

Our favourite varieties

Calamagrostis acutiflora Karl Foerster - Feather Reed Grass

This must-have variety, most widespread in gardens. It is very decorative, with large clumps of green foliage that turn golden in autumn, topped by 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 distinguished by truly feathery, light flowering, becoming shiny and silvery in sunlight, which earned it the nickname 'Diamond grass'. 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 distinctive trait of offering variegated foliage of cream-white–yellow, making it brighter than other varieties. It also bears light, silvery, slightly purplish panicles.

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

See the product sheet

Calamagrostis acutiflora Avalanche - Feather Reed Grass

This variety offers striking, original foliage, green, marginate with white, topped from early summer by brown-purple flower spikes that later turn blonde. It prefers moist, well-drained soils.

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

See the product sheet

Calamagrostis acutiflora Waldenbuch - Feather Reed Grass

This fairly compact variety is suitable for small gardens. It forms clumps of fine, supple green leaves that turn yellow later in the year. From June it also bears 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 sun, possibly in partial shade (for example if you live in Mediterranean region). 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 striking than when in shade.

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

Calamagrostis can be planted singly (for example on a short grass meadow), or in small group of three to five clumps, to bring a bit of structure and volume to a garden… You can even plant it in a large group to create a border or hedge, or to obtain a homogeneous, airy backdrop to a planting bed. As it is a fairly tall plant that remains decorative all year round, you can use it to hide a fence, low wall or barrier. Although it prefers to be planted in ground, it is possible to grow Calamagrostis in a large pot or container.

When to plant?

We recommend planting Calamagrostis in spring. However, it can also be planted at other times of year; most important is to avoid periods of frost or extreme heat.

How to plant?

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

1. Place rootball in a tub filled with water. This rehydrates it.
2. Dig a planting hole, which ideally should be two to three times size of rootball.
3. Take rootball out of its pot, loosen roots slightly, then place it in the planting hole. Top of rootball should be level with soil.
4. Backfill soil all around and firm down with flat of hand.
5. Water generously.

You can also grow Calamagrostis in a large pot or container. Lay a drainage layer at bottom (gravel, clay beads, pottery shards…), add a light, free-draining substrate (for example potting compost mixed with a little sand) and plant. Water.

We recommend continuing to water regularly during first weeks, until plant is well established. Afterwards, it will tolerate drought fairly well.

Discover also our advice sheet on planting grasses.

Care

Calamagrostis tolerate fairly dry soils and do not need much watering. You can water only in the weeks following planting, then perhaps during dry spells. However, if you grow them in pots or containers, watering will need to be more frequent. Similarly, Calamagrostis brachytricha and Calamagrostis epigejos will prefer slightly cooler soil than other species and will therefore require more frequent watering. You can use mulch to help keep soil cool.

Calamagrostis remain decorative in autumn and winter, but they should be pruned at end of winter (February–March), just before they restart their growth. Prune severely by cutting the clump back to 10 cm above soil level.

You can also do a light tidy-up in autumn by removing damaged stems or leaves.

If you grow Calamagrostis in pots or containers, remember to repot them from time to time, preferably in early spring.

Feel free to cut the inflorescences for 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, care…), it is a resilient plant that rarely encounters cultivation problems!

Propagation

Like most grasses, Calamagrostis is propagated by division of clumps.

Clump division

Division is carried out in early spring, when the plant is just beginning to resume its growth.

1. Dig up a clump by digging wide enough around it and gently lifting it from the soil to avoid damaging the roots.
2. Divide it into several pieces. Ensure each piece has roots. Preferably use pieces taken from the outer edge of the clump.
3. Prepare the soil and replant each new clump.
4. Water generously afterwards to encourage their regrowth.

Monitor the new clumps and continue watering them over the following weeks.

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

Discover 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 informal, abundant look full of life. Create a superb scene by pairing Calamagrostis ‘Karl Foerster’ with Verbena bonariensis and Echinacea purpurea. Also make use of the flower spikes of persicarias or knotweeds! Establish a wild meadow with many herbs and grasses, punctuated by small colourful flowers (scabious, mallows, corn 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 moist soils.

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

With their vertical, airy appearance, calamagrostis are also ideal for creating a graphic, modern garden. These large grasses will help structure the border. They form upright, tall clumps, adding verticality; use them to play with textures and shapes. Place a few clumps of Calamagrostis alongside lower-growing plants such as lady’s mantle, heucheras, Ajuga reptans, hardy geraniums, bergenias, carex… Calamagrostis is perfect for lightening a somewhat flat border and restoring volume. Scatter a few clumps among other structural plants such as Eremurus, Agapanthus and Veronicastrum.

Calamagrostis soften straighter shapes and strict lines.

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

Create a superb late-season scene in autumn–winter with plants in purple, beige, brown, bronze or orange tones. Choose, for example, Asters, Dahlias, Echinacea ‘Tangerine Dream’, Sedum ‘Autumn Joy’, evergreen grasses… Prefer plants with a loose, transparent habit whose flowers and foliage catch sun rays, frost or raindrops… Plants you can leave in place, whose structure, infructescences (seedheads) or berries remain decorative in autumn–winter. Choose Echinops, Eryngiums, Dipsacus fullonum, Perovskia, Phlomis… For decorative berries, choose Callicarpa, Symphorines or Euonymus. Also enjoy decorative foliage and bark, notably from 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 create a no‑maintenance garden! They are perfect for planting in parts of the garden that receive little attention because, apart from cutting them back once a year at the end of winter, calamagrostis require very little care. Create a natural area that is ecological, water‑wise and low‑effort. Choose other grasses, drought-tolerant plants, groundcovers and plants that naturalise and return each year.