How to grow calamagrostis

What are calamagrostis?

These striking ornamental grasses have tall, upright, feathery plumes that stand above clumps of gently arching leaves. They are deciduous perennials, meaning they live for many years, with the leaves and seedheads dying in autumn, then sprouting afresh from the base in spring.

They are easy to grow, preferring full sun and rich, moist soil, but they will tolerate semi-shade and most soil types. They dislike deep shade and overly dry soil.

Choosing calamagrostis

There is a limited range of species and cultivars to choose from, but the variations between them give each a different look. The usually feathery flower plumes, which stand on strongly upright stems, range in colour from silvery to pink to purplish-brown, fading to beige by autumn and through winter.

Some have variegated leaves with fine white or golden-yellow stripes.

To browse photos and descriptions of calamagrostis cultivars, go to RHS Find a Plant.

Calamagrostis are versatile grasses that suit a wide range of garden styles, from prairie plantings to perennial borders or contemporary settings, where their upright form makes a bold statement.

They can be used in various ways in borders:

• These tall grasses are usually positioned at the back of borders, although they can also work nearer the front to provide variation in height and texture

• They can be woven through borders in a narrow ribbon or wider swathe

• They can provide a backdrop for other perennials, allowing their colourful flowers to stand out 

• They work well planted in groups with other grasses, using contrasting shapes, leaf colours and flower types

• They can be planted as an informal screen

For further planting ideas and information on how best to work with calamagrostis, see our guide to ornamental grasses.

As calamagrostis tend to be tall, do check the height and spread before buying, to make sure you have space to accommodate them.

Ornamental grasses: selection

Ornamental grasses: selection

How and what to buy

Calamagrostis are usually available in garden centres from spring to autumn, although the choice may be limited to the most popular cultivars, such as ‘Karl Foerster’ and ‘Overdam’.

For a wider selection, try nurseries and online suppliers specialising in ornamental grasses, such as Knoll Gardens and Beth Chatto’s Plants.

The plants are sold in containers, usually 1–2 litres, for immediate planting.

Use RHS Find a Plant to track down stockists of specific cultivars.

Buying: mail order plants

Buying: mail order plants

RHS guide to buying healthy plants

RHS guide to buying healthy plants

When to plant calamagrostis

For best results, plant in autumn while the ground is still relatively warm and the roots will begin to grow and establish into the surrounding soil.

You can, however, plant at any time of year, as long as the ground is not frozen or waterlogged.

If you plant in summer, be prepared to water regularly, as plants are particularly vulnerable to drying out when their roots have not yet spread out into the soil.

Where to plant calamagrostis

• Calamagrostis thrive in full sun. They will tolerate partial shade, but will probably grow lopsided, leaning towards the light 

• They prefer soil that stays moist during summer. If your soil tends to dry out, dig in plenty of organic matter before planting, and be prepared to water regularly, especially in summer

How to plant calamagrostis

Calamagrostis are easy to plant, in a similar way to most perennials and other ornamental grasses.

Spacing will vary though, depending on the cultivar's ultimate width (see plant label) and the effect you want to create:

• To grow as an eye-catching individual specimen, space 1m (3⅓ft) from any other plants

• To create a bold block or swathe of grasses for maximum impact, space plants 45cm (18in) apart 

• To form a ribbon (or continuous wavy line) of grasses weaving through a border among other perennials, space plants 45cm (18in) apart

Perennials: planting

Perennials: planting

Watering

• Water newly planted calamagrostis regularly for at least the first year, especially in warm weather and dry spells

• Once established, if the site is naturally damp, calamagrostis should need little or no watering

• In free-draining soil that dries out, you will need to water regularly for at least the first two to three years, aiming to keep the soil moist but not soggy

• During long spells without rain, check regularly to see if the soil is dry. Also look for rolled-up leaves, which indicate the plant needs water

• When watering, give a good soak to thoroughly wet the top 15cm (6in) of soil

Water: collecting, storing and re-using

Water: collecting, storing and re-using

RHS video guide to watering efficiently

RHS video guide to watering efficiently

Feeding and mulching

Grasses do not generally require feeding.

Instead, you can enrich the soil and increase moisture retention by:

• digging in plenty of organic matter before planting – ideally one bucketful of well-rotted manure or garden compost per sq m (sq yd)

• apply mulch to the surrounding soil, in a layer about a 5cm (2in) thick, annually in late winter or early spring

Deadheading

• The feathery flower plumes and seedheads are the main attribute, so leave them in place for as long as possible, through autumn and winter. They look particularly ornamental in the low winter sun or when laced with frost

• Finally remove them in late winter, along with the dead foliage, to make way for new shoots in spring

• Flower plumes that get broken or flattened by the weather can be removed at any time

Overwintering

Calamagrostis are hardy, so can be left in place in borders all winter. However, they are deciduous, so the top growth will die back from autumn onwards, then re-sprout from the base in spring. 

Caring for older plants

• Cut back the whole plant to the base annually in late winter to prevent the old dead material clogging up the clump

• Mature, overgrown clumps can be refreshed by dividing in spring (see Propagating below)

• The whole clump should be cut down at the end of winter (late Jan/Feb) to allow the new shoots to grow unimpeded

• Use sharp shears or secateurs, and cut about 2cm (1in) above ground level

• Make sure you prune before fresh green shoots start to appear at the base, to avoid damaging the new growth when you cut

• All the dead material can be chopped up and composted

By division

The easiest way to make new plants is by dividing a mature clump in early spring. This will produce several new, smaller plants, each identical to the parent. The new plants should settle in quickly and may even flower the same year.

It's a great way to extend your current plantings or you can share spare plants with friends. 

It has the added benefit of helping to revive overgrown or congested clumps.

See our step-by-step guides below.

Perennials: dividing

Perennials: dividing

RHS video guide to dividing perennials

RHS video guide to dividing perennials

By seed

The seeds of calamagrostis are mainly sterile, which means they won’t self-seed around the garden. However, that also means you are unlikely to have much success if you collect seeds to grow new plants.

Calamagrostis are fairly robust grasses and enjoy good health when given the growing conditions they enjoy.

• Avoid rust diseases by dividing overcrowded clumps to improve air circulation and reduce the humidity that this fungal disease needs

• A lack of flowers can be caused by too much shade. Move the plant to a more open location or trim back surrounding shrubs to reduce the shade

• In rural settings, tunnelling voles and nibbling rabbits may be troublesome

More advice

If you're a member of the RHS, you can use our online Gardening Advice Service, via MyRHS, for any gardening problems or queries.