Love them or hate them, ornamental grasses are here to stay. To critics, their value is incomprehensible: to them, even the most ornamental miscanthus is the same thing as the coarse rye grass found in the farmer’s field.
I disagree. What else gives you such contrast in shape and texture compared to other plants — such as the vertical line posed by a calamagrostis and loved by designers, for instance? What else sways in the lightest of breezes like deschampsias and stipas, bringing movement and rhythm to borders? On top of these graces, grasses are easy to maintain, with few diseases.
You do need to choose them carefully, however. Some are too flimsy and get pushed about by the slightest wind; other coarse-textured varieties only belong in the savannah. Some bury their flower heads in their leaves and look short-necked; some don’t flower at all, and others are just plain messy with no body, little texture and a short season.
They must also be used with care. Whole gardens have been devoted to grasses, with little thought given to other plants, but it is difficult to carry off this sort of planting.
Varieties can be combined as long as there are other plants to provide a break. Large cannas, Verbena bonariensis, Michaelmas daisies, monkshoods, rudbeckias, sedums and echinaceas are all suitable companions for the finer-textured grasses, which can then stand free of their neighbours. Visually, space is important: clutter grasses, and you will lose the effect of those solitary fountains punching the air like exclamation marks.
Cortaderia selloana, the pampas grass of Argentina, is one of the most common grasses. It makes an impressive landscape plant: its large, creamy, ostrich-plumed flowers top stiff 8ft stems, rising from a tussock of grey-green (and razor-sharp) leaves. Flowering starts in September and lasts for several months. The form ‘Monstrosa’ is even bigger — some 10ft high. These grasses aren’t suited to the smaller garden, although you do occasionally see one dramatic pampas filling a front yard.
The dwarf version, C selloana ‘Pumila’, with flowers 6ft high, is more manageable. It has a neat, tidy habit and all the good qualities of the parent. At Great Dixter in East Sussex, where I garden, it is planted near the dusky- orange, red-hot poker, Kniphofia linearifolia, which flowers in October.
Perhaps the most spectacular flowering grass is the statuesque Spanish oat grass, Stipa gigantea. This flowers early to mid-summer and still looks impressive in late autumn. Upright, 6ft-high stems, with loose clusters of oat-like flowers, rise from dense clumps of thin, evergreen leaves, and the golden-brown blooms glow in the evening sun. It is light and diaphanous, so despite its height it can be placed at the front of a border, and is also useful in small gardens.
Also high on my list of favourites is Calamagrostris brachytrica, the upright stems of which carry ash-brown, foxtail-like flowers in late summer. At 6ft high and 3ft across, this makes a neat clump and is useful in narrow borders. It goes particularly well with the rich blue Aconitum x carmichaelii ‘Kelmscott’ and the annual ‘Kiss Me Over the Garden Gate’ (Persicaria orientalis), which has bright pink tassels dangling from slender, 6ft tall stems.
Undoubtedly, the miscanthus are the most widely used grasses in gardens today; they range from compact varieties such as ‘Yakushima Dwarf’ (3ft), to architectural monsters such as Miscanthus x giganteus (10ft). With arching leaves and silky, pink-brown flowers shaped like shuttlecocks, miscanthus can play a vital role in the late-summer garden. Some develop rich autumn colour and then bleach brown, remaining highly ornamental well into winter.
Some hardly flower at all in our British climate, but make handsome foliage plants. Two variegated forms stand out. The first is Miscanthus sinensis ‘Strictus’ (6ft 6in), an erect, almost spiky plant with yellow horizontal banding on its stems and leaves. I think it has more impact than Miscanthus sinensis ‘Zebrinus’, which is similar, though with a looser habit. Used among bun-shaped perennials and shrubs, ‘Strictus’ gives a contrasting, upright shape.
There are plenty of flowering miscanthus to choose from. ‘Hercules’ (6ft-plus) has silvery- brown flowers with a touch of pink. These are held well above the foliage and gracefully presented on arching stems.
Smaller, at 5ft, well proportioned and full of flower is ‘Kleine Fontane’, which has an upright habit with pinky-brown tassels, again held above the leaves. ‘Ferner Osten’ is another favourite. About 6ft tall, it forms a well-balanced plant; its abundant flowers are rich red in bud, and turn beige when open. ‘Flamingo’ is the same height but has a slightly more arching habit with pink flowers, followed by beautiful autumn colours turning from green to bright orange to gold. ‘Malepartus’ (also with terrific autumn colour) is one of the best and is well known for its large, wine-red flowers in late summer. It has a neat, upright habit and a sturdy frame, flowering profusely from late August onwards.
The switch grasses, Panicum virgatum, and its cultivars are also useful. These are 5ft-6ft 6in high and dainty: an abundance of small flowers gives a misty effect, and can contrast well with other, heavier border plants. The varieties ‘Rubrum’, ‘Shenandoah’ and ‘Hanse Herms’ are well known for their reddish autumn colour. ‘Heavy Metal’ has a grey-green appearance, but is nonetheless valuable for its graceful structure.
No matter how delicate these panicums look, don’t be deceived. They are resilient and hardy in extreme temperatures (both hot and cold), tolerate wind, bounce back into shape after snowfall and keep their handsome appearance well into February.
The pennisetums, with their bottlebrush-shaped flowers and arching habit, offer a marked contrast to many of the other grasses. Particularly striking is Pennisetum alopecuroides var purpurascens, which rises 2ft and has blackish flowers. The clone ‘Black Beauty’ is new on the scene, and is taller and even darker. Pennisetum macrourum is tall and upright, with long, pale-cream flowers resembling pipe cleaners. The tender P setaceum ‘Rubrum’ is mouthwatering, with chocolate-coloured foliage and flowers. All are full of character and worth having.
Molinia caerulea subsp ‘Transparent’ has wonderful long arching stems and loose panicles of bead-like flowers sitting on the branches — they look like water droplets, and the overall effect is like a delicate fountain spray. The stems rise from a clump of rich-green leaves, so the plant has body but is elegant. In autumn, the whole thing turns brilliant golden-orange before collapsing.
From ampelodesmos to chasmanthium and oryzopsis to sesleria, there are many more to discover. A word of advice: grasses generally hate being divided in the autumn. Cut them down, split and replant in the spring. Do this only when the plant develops a bald patch in its centre. There’s no reason to set fire to them as is traditional, as this can do more harm than good.
