Grasses In Containers

Grasses are generally tough plants which seem well able to cope with the stresses so often experienced by container plants. In the heat of summer, plants in outdoor pots may need watering more than once a day and, because of the confined space for their roots, they demand regular feeding.

The elegant forms and subtle leaf colors of grasses are highlighted when they are treated as specimen container plants, looking their best when grown singly. The distinctive shapes of containers and grasses may be combined in innumerable ways. Erect grasses in round pots look dramatic, whilst arching grasses may be seen to full advantage in tall containers with straight sides.

Even familiar garden grasses are elevated in importance when they are grown in a container. The details of the plant are emphasized through its isolation and its being brought closer to eye level. For the miniature gems of the grass world, which might otherwise be swamped by larger plants in the open garden, this treatment is ideal. As components of miniature landscapes they may be grown in sink gardens, on which the alpine enthusiast can lavish as much care as necessary to keep them in prime condition. An alpine gem from Spain is Alopecurus lanatus. It has spiky, blue-grey leaves that are covered in fine hairs, giving it a woolly appearance. To survive, this and its taller relative A. antarcticus need full sun and perfectly draining soil. In a container it is easy to supply the right growing medium and to bring the plants under cover in the winter to protect them from excess damp. Two more miniature grasses require similar treatment and will reward you by producing clumps of fine blue-green leaves. The smaller Poa tasmanica very slowly forms mats of ice-blue leaves no more than 2.5cm/1in high; Festuca glacialis is slightly taller and forms darker dense mounds of very fine foliage. There is also a sedge, Carex firma 'Variegata', which is seen to best advantage in a pot or sink garden. Its straight, rigid leaves form small prickly mounds no more than 2.5cm/1in across. This grass prefers damper growing conditions and tolerates partial shade.

Larger grasses with an arching form are shown to advantage when grown in containers. Of these, the most exciting example has to be Hakonechloa macra 'Aureola', its brilliant, yellow-variegated leaves remaining attractive throughout the summer. This is a relatively slow-growing grass which benefits from the absence of competition afforded by growing in a container. Carex siderosticha 'Variegata' is similarly slow-growing, its handsome broad arching leaves margined white with a pink flush at the base.

Grasses with a more upright form are another group which make excellent candidates for container growing. A subtly colored variety that looks outstanding in a pot is Chionochloa rubra. This is fairly large, reaching 75cm/30in in maturity, with fine, evergreen leaves suffused with a brassy shade of ochre on their upper surface. Stranger still are the colors found in some of the sedges. Carex buchananii, C. kaloides and C. petriei are rather similar species which have been regularly confused in nursery catalogues. Whilst each is distinct, all possess a stiff upright habit and leathery leaves in extraordinary shades of brown. Their strange unreal appearance sets them apart from other grasses, thus making them ideal candidates for isolating as container specimens. Similarly, the tight, spiky clumps of many of the blue-leaved fescues can look artificial. These plants adapt particularly well to container growing and are ideal for an exposed roof top or balcony.

Large grasses grown in containers make impressive specimen plants for: the patio or conservatory and can act as focal points or serve as moveable screens. Bamboos are the only large grasses regularly seen growing in containers, bringing a hint of the Orient to any corner in which they are placed. The problem with a number of bamboos is their propensity to spread aggressively in the garden but, once they are confined to a container, the danger is eliminated. A perfect candidate is the attractive, but invasive, yellow-variegated bamboo Pleioblastus viridistriatus. This is widely available and a tempting choice that has given many gardeners cause to regret planting it in the open garden. The smaller growing selections of Miscanthus sinensis, such as 'Morning Light; 'Sarabande' and 'Yakushima Dwarf', also adapt well to container growing as long as the soil is well drained and is not allowed to become too wet in the winter. Inevitably, all of these larger grasses become pot-bound, and need dividing and replanting in fresh compost every few years.

The range of garden grasses can be increased by growing tender species in pots and sheltering them indoors during the winter. Papyrus are popular house plants and yet they benefit greatly from a summer outdoors, perhaps gracing the margins of a pool. Their stiff stems, topped with leaves arranged like the spokes of an umbrella, introduce a unique and exotic atmosphere into any garden. Cyperus papyrus, a plant which can easily attain a height in excess of 2m/6 1/2 ft, and its cousin C. involucratus at around 1m/3 ft, are the most frequently encountered species. A similar situation also suits the frost-tender variegated version of the giant reed, Arundo donax 'Variegata'. This is one of the most spectacular of all grasses and may attain some 3m/10 ft in height when grown well. Lemon grass, Cymbopogon citratus cannot claim to be as attractive, but its increasing popularity with cooks may earn it a place on the summer patio. Its rather stiff upright leaves can exceed 1m/3 ft in length, and the plants can develop into quite imposing specimens. A number of the grasses grown as annuals in Europe are actually perennials in warmer climates. Species such as Pennisetum setaceum and P. villosum, for example, can be grown in pots to allow them to be moved inside during the winter. In this way they develop into large plants that flower earlier and more reliably than smaller seeded plants.

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