Ornamental grasses

Cultivation notes

Ornamental grasses tolerate a wide range of conditions, but most like a sunny position in light, moist but well-drained, moderately fertile soil.

They do not need much feeding; this can encourage lush foliage at the expense of flowers. One application of a balanced fertiliser in spring is adequate.

Planting

It is important to plant grasses at the correct time.

• Grasses from cool climates such as Deschampsia, Festuca, Helictotrichon and Stipa come into growth in late winter and flower before mid-summer and so should be planted in autumn for the best establishment
• Grasses from warm climates such as Miscanthus, Panicum, Pennisetum and Spartina come into growth in late spring, flower after mid-summer and are usually cut back in late winter. They are best planted in late spring

Container cultivation

Grasses are good plants for containers. Use loam-based compost such as John Innes No 2 with 20 percent loam-free compost to lighten the mix. Evergreen grasses such as Carex combine well with winter bedding to give height and a contrast in texture.

Pruning and training

The foliage on deciduous grasses can be left until February for its structure and movement in the depths of winter when any contribution to interest in the garden is welcome.

For advice on when to cut back evergreen and deciduous grasses, see our page ornamental grasses: cutting back.

Propagation

Division is one of the main ways to increase your stock of grasses. Carrying this out at the right time of year is important.

Some grasses such as Carex pendula or Stipa arundinacea seed themselves prolifically to the point of being invasive. For less easy to germinate grasses, collect well-developed flower heads just before the seeds are fully ripe, and ripen them in brown paper bags indoors.

Sow the seeds fresh at a temperature of 10°C (50°F), or store them and sow them in spring.

Cultivar Selection

There are some super grass or grass-like plants to choose from on the RHS Plant Selector. Here are a few top performers;

• Cortaderia selloana ‘Pumila’ AGM – pampas grasses have been much maligned, but this smaller cultivar is elegant and mixes well with other perennials and shrubs. Height: 1.5m (5ft)
• Festuca glauca ‘Elijah Blue’ – one of the bluest of fescues, ‘Elijah Blue’ forms a spiky dome. Trim back every few years in March to get rid of dead leaves. Height: 40cm (16in)
• Miscanthus sinensis ‘Morning Light’ AGM – a compact cultivar with slim cream margins to its leaves, this miscanthus is ideal for small gardens and even containers. Height: 1.5m (5ft)
• Pennisetum villosum AGM – the fluffy rabbits-tail-like seedheads of this grass are an instant attraction. Not the hardiest: needs sun and free drainage for the best results. Height: 60cm (2ft)
• Stipa tenuissima – the fine blades of this grass dance even in light winds. Cut back in spring for fresh green growth, which ages to soft gold by late summer. Height: 60cm (2ft)
• Deschampsia cespitosa 'Goldtau’ (syn. 'Golden Dew') – compact and graceful, this grass has spikes of airy, reddish-brown flowers. Tolerant of shade and damp conditions, it is can be grown in gardens unsuited to many other ornamental grasses. Height: 75cm (30in)

Links

RHS Plant Finder
AGM plants
Miscanthus trials bulletin (Adobe Acrobat pdf)

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Cortaderia selloana 'Pumila'

Carex elata 'Aurea'

Pennisetum flowers

Problems

Ornamental grasses generally suffer from few problems if they are planted in an appropriate position for their needs.

Occasionally, rabbits and voles may be troublesome.