How to grow ornamental grasses
Grasses are easy to grow, versatile and beautiful. With their fountains of elegant foliage and plumes of feathery seedheads, they bring drama and movement as they sway in the breeze. They're a great asset in any setting, from traditional to contemporary, formal to relaxed, mingling well among other plants or as stand-alone features. Every garden should have plenty!
- Easy to grow
- Flowers in summer and autumn, with seedheads into winter
- Plant in autumn or spring, depending on the type
- Cut back deciduous types in late winter to spring
- They need very little ongoing care
- Make new plants by dividing clumps or sowing seeds
- Most like a sunny, open site, but there are grasses to suit most locations
All you need to know
Ornamental grasses come in all shapes and sizes, and thrive in a wide range of conditions, so it’s important to choose one that suits your planting site. Check plant labels carefully before buying to ensure the plant's habit will suit your planting site, as well as whether it will thrive in the conditions your garden provides. For more information, read our advice on assessing the microclimate of your garden.
Getting the right look
Consider what you want from your plant, such as:
- Size – do you have a large space to fill, a small gap in a border, or do you want some low ground cover? Heights and spreads range from 25cm (10in) or less to 3m (10ft) or more.
- Style of growth – do you want a bold, vertical plant, or a soft mound of arching leaves and cascading seedheads?
- Evergreen or deciduous – do you want an all-year-round feature or one that is cut to the ground in late winter and sprouts afresh every spring?
- Colour – choose from foliage in all shades of green, as well as acid yellows, coppery tones, steely blues and flashes of red.
- Vigour – do you want a neat, non-spreading clump or do you want to fill a large area quickly (although beware that some spreaders can become invasive).
- Best features – do you want striking ornamental seedheads or primarily just beautiful foliage?
How and what to buy
Where to get ideas and advice
To explore and narrow down your potential planting choices, you can:
- Visit gardens that feature lots of ornamental grasses and see which ones you like best. Late summer and autumn are good times to view them in their prime. All the RHS Gardens feature ornamental grasses, and all the plants are labelled, so you can note down your favourites.
- Ask at local garden centres, which should offer a range of grasses that do well in your local conditions.
- Go to RHS Find a Plant – search for ‘grasses’ to browse the photographs and plant descriptions, and find out where to buy them.
- Visit a specialist nursery, in person or online.
When to plant
it is important to plant certain grasses at the correct time:
- Autumn is the best time to plant grasses from cool climates, such as deschampsia, festuca, helictotrichon and stipa. These come into growth in late winter and flower before mid-summer.
- Late spring is ideal for planting grasses from warm climates, such as miscanthus, panicum and pennisetum. These come into growth in late spring, flower after mid-summer and are usually cut back in late winter.
Where to plant
Ornamental grasses tolerate a wide range of conditions, but most like an open, sunny position in light, moist but free-draining, moderately fertile soil.
Grasses also thrive in large containers. You can either plant one variety of grass for a striking effect, or use a smaller grass alongside bedding or flowering perennials. Grasses add height and a contrast in texture to a mixed container display. Grass-like evergreen sedges, such as carex, can be used in a winter container planting.
How to plant
In the garden border
Read our advice on planting perennials, such as grasses.
Use loam-based compost such as John Innes No 2, combined a loam-free multi-purpose compost to lighten the mix, at a ratio of about four parts to one.
For more information, read our advice on planting up containers.
Keep new grasses well watered
Water newly planted grasses regularly for at least their first growing season, especially during hot weather. After that, most grasses will be fairly drought tolerant.
Ornamental grasses growing in the ground require very little routine care.
Those in containers need some extra watering and feeding. For more information, read our advice on maintenance for plants in containers.
To keep plants looking neat, you could occasionally remove any damaged foliage or broken flower stems. Combing out any dead leaves and decris from the clump benefits evergreen grasses when tidying them.
Newly planted grasses should be watered regularly during their first summer. After that, most grasses growing in the ground are fairly drought tolerant and shouldn’t need additional watering except during prolonged hot or dry periods.
Grasses in containers can dry out quickly, so should be watered regularly during the summer.
In the wild, grasses often grow in quite poor soil, so in the garden, one application of fertiliser in spring is usually sufficient. Generous applications of fertiliser tends to encourage lush foliage at the expense of flowers.
Grasses in containers have less access to nutrients, so can benefit from a general-purpose liquid feed through the growing season: March to October
A few grasses may need to be kept in check themselves, including:
- Spreading types that are often used as ground cover, such as gardener's garters (Phalaris arundinacea var. picta).
- Enthusiastic self-seeders, such as annual greater quaking grass (Briza maxima) and Carex pendula. These can either be deadheaded before the seeds fall or grown in an informal meadow-style planting. Many other grasses will self-seed, but not usually excessively – simply remove any seedlings that you don’t want, or move them to your preferred spot.
See Pruning and Training below.
Caring for older plants
Over time, some grasses can grow into very large, overcrowded clumps, so it is best to lift and divide clumps every five years or so. This helps to keep the plant healthy and vigorous, and also gives you new plants to add to your garden or give to friends.
For more information, read our advice on dividing ornamental grasses.
When cutting back grasses that have sharp edges to the leaves, be sure to wear protective gloves.
The pruning requirements of deciduous ornamental grasses, which have foliage that dies off in autumn, are different to those of evergreen types, which have foliage that stays alive all year.
The foliage and seedheads of deciduous grasses turn straw-coloured in autumn, but should be left in place over winter to provide structure and movement. They look particularly spectacular laced with frost.
The seedheads also provide food for seed-eating birds such as finches, while the foliage gives winter shelter to insects and other small creatures.
However, the wind-battered old growth does need to be removed before new shoots sprout from the base in spring. Simply shear it all off close to the ground – see our guide to pruning grasses.
You can neaten these up in early spring by removing any faded seedheads. Any dead or damaged foliage, can be combed out with the fingers, leaving the living, healthy leaves in place. For more information, read our advice on cutting back ornamental grasses.
The easiest way to propagate grasses is by lifting the clump and dividing it into several smaller sections, then replanting these. Digging up large, heavy clumps may be a two-person job.
Division must be carried out at the right time of year:
- Late winter or early spring for cool-season grasses, which come into growth early in the year. These include carex, calamagrstis, chasmanthium, deschampsia, festuca, hakonechloa, molinea and stipa.
- Late spring for warm-season grasses, once they are in active growth, which happens later in the year. These include arundo, cortaderia, imperata, miscanthus, panicum, pennisetum and phalaris.
For more information, read our advice on dividing grasses.
Many grasses can be grown from seed, but some germinate more easily than others.
Prolific self-seeders, such as Carex pendula, grow readily from seed, but can become invasive.
For grasses that germinate less readily:
- Cut well-developed flowerheads just before the seeds are fully ripe.
- Put the whole seeedhead in a large paper bag, bring indoors and allow the seeds to ripen naturally.
- Sow the seeds in autumn at a temperature of 10°C (50°F), or store them cool and dry over winter and sow in spring.
For more information, read our advice on collecting and storing seed.
Ornamental grasses generally suffer from few problems if they are planted in a position that suits their needs. However, they may occasionally have difficulties with:
- Rust – this fungal disease appears as rusty-coloured patches on the leaves. It can be largely avoided by dividing overcrowded clumps and allowing better air circulation around plants.
- Lack of flowers – this is usually caused by insufficient light. So reduce the shade from neighbouring shrubs or move the grass to a more open position. Overfeeding can also promote leaves at the expense of flowers
- Rabbits and voles – these will eat some types of grasses.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.