On the beach at Poole, Dorset, England, the native lyme grass, Leymus arenarius, must cope with a combination of full sun, reflected heat from the sand, frequent drying winds and ultra-dry, continually shifting ground.
Design sets down the basic forms but soon the garden is in nature’s grip. Then, with careful nurturing, the garden’s performance will outshine your imagination.
—Wolfgang Oehme and James van Sweden
Bold Romantic Gardens
PLANTS ARE HAPPIEST, and therefore easiest to look after, when growing under conditions they enjoy or at least easily tolerate. A thoughtful look at the established plant communities in natural systems shows us that plants arrange themselves into areas that best suit their needs or to which they have become adapted. Over time, a process of natural selection matches the right plant to the right place.
In our gardens this natural process is interrupted and replaced with a variety of other considerations that can have very little, if anything at all, to do with matching plant with place. However, the more we can understand our gardens’ basic growing conditions, the better we will be able to match the most suitable plants with those conditions, and so the better our gardens will be.
Easy as they are, grasses have their likes and dislikes, their preferences as to position and soil—all based on where they come from in nature. Luckily for gardeners, a huge number of grasses are actually quite happy in a wide range of average garden conditions. However, in this chapter we will look at some of the more challenging environments that can be found in gardens, exploring which grasses might be best suited to these conditions.
By far the greatest number of grasses come from open and sunny, if not outrightly dry and drought-prone, natural areas—so there is a very large number of grasses from which to choose for varying degrees of dryness and drought.
Whether on a beach in the constantly shifting sand dunes of mild maritime climates or in the harsher conditions of more arid, desert-like areas, drought and sun-baked conditions involve a shortage of water for at least part of the year. Combined with high summer temperatures, drying winds and often gravelly well-drained soils, such conditions will literally ‘cook’ or ‘fry’ all but the most resilient of plants.
Under drought conditions most plants, especially those with large leaves such as hostas and ligularias, will show signs of short-term stress by visibly wilting. Grasses can be tough customers under such short-term stress, appearing hardly to notice the lack of moisture, though many will eventually roll or curl their leaves so that they present less surface area to the daytime sun until sufficient moisture returns. For grasses that have specialized in extreme conditions like the beach grasses—the marram, Ammophila, or wild rye, Leymus—adaptations such as tough waxy leaves and a questing root system allow them to survive and indeed thrive where few others can follow. Where prolonged summer droughts are a regular feature, such as in mediterranean areas, many grasses including Aristida, Bouteloua, Melica and Nassella in common with other regionally adapted plants will go into summer dormancy, shutting down active growth during the hottest and driest months of the year and then starting back into growth with the arrival of the autumn rains. In drier desert-like conditions where water is an unreliable and occasional luxury, grasses will remain in active growth only while there is sufficient moisture in the ground.
For the gardener, such drought-adapted qualities can also be marked out by the presence of grey or blue foliage. Elymus, Festuca, Helictotrichon, Leymus, Poa and Sesleria are all drought-tolerant grasses that have the signature blue-tinted foliage which has a very ornamental quality much prized by gardeners and can be grown easily in most sunny dry soils. For warmer climates Leymus condensatus, especially in its superb form L. condensatus ‘Canyon Prince’, is perhaps unrivalled for providing strong mounds of comparatively wide icy blue foliage especially when topped by its magnificent flowers, while for less favoured areas Leymus arenarius will contribute something similar though on a lesser scale.
On a smaller scale again, Helictotrichon sempervirens is a wonderful clump-forming ‘blue’ that forms a very attractive rounded outline composed of stiff leaves that make a distinctive contribution wherever it is used. Even smaller, Festuca is a very wide and adaptable family with almost-hair-like narrow leaves that offers perhaps the greatest number of different cultivars including those deriving from Festuca glauca. Of these, Festuca glauca ‘Elijah Blue’ is perhaps one of the most reliable performers. As all festucas seed readily it is important to choose cultivated selections from a reliable source as so often inferior seedlings have become mixed with the original cultivar material. The widespread and highly adaptable Festuca rubra has some wonderful offerings including the steely blue-grey of F. ‘Molate Blue’ and the lighter blue-grey of F. ‘Patrick’s Point’. Smaller still, and definitely underused, is Sesleria caerulea whose tight mounds of evergreen bicoloured green and blue-grey leaves are tough and durable even in some shade in warmer areas.
Garden conditions in urban areas can present a similar set of challenges, whether in small domestic gardens, on roof terraces or even in those areas that surround commercial buildings or public areas in our towns and cities. Growing conditions in these places can be just as trying for plants as in any natural environment. The combination of hard paved areas such as roads, parking areas, roofs and walls all contribute to the creation of heat islands; heat from the sun, from buildings and from vehicles is reflected and radiated by the hard surfaces which at the same time prevent much-needed water from reaching and replenishing the ground, redirecting it through storm drains away from where it is perhaps most needed. The result is a continually warm environment that is short on water (for all intents and purposes, a desert).
In the relatively cool conditions of Arroyo Grande, California, a gravel pathway meanders through informal plantings including Carex testacea, Festuca and Helictotrichon, in the garden of Dave and Rainie Fross.
Well known for its hot, dry, desert location, Las Vegas, Nevada uses drought-adapted grasses to great effect. From the stunning pink muhly, Muhlenbergia capillaris, in the car park (parking lot) of the unique Springs Reserve to Pennisetum ‘Fairy Tails’ surrounding an upscale shopping mall, a simple but refined palette of grasses provide an effective, visually pleasing solution to hot, dry environments.
In this motel garden in Monterey, California, clearly rounded but spiky foliage of Helictotrichon sempervirens contrasts with rock, slab, bark and building. Blue-tinted foliage is mostly an adaptation for sunny drought-prone areas; the colouring becomes more pronounced the more extreme the conditions.
Other members of the beautiful muhly family include Muhlenbergia rigens with its immediately distinctive outline and M. rigida whose seductive pink flowers are especially vibrant in the form ‘Nashville’. Both tolerate hot dry conditions, as does M. lindheimeri and others such as the quite unique bamboo muhly, M. dumosa. Coming from warm desert-like areas, the bamboo muhly has insignificant tiny yellow flowers but its bamboo-like woody stems and leaves place it firmly in the top flight of all foliage plants. Revelling in hot mediterranean-type climates, the bamboo muhly’s adaptability allows it to grow successfully in much less favoured localities such as at RBG Kew, London, in the ground and also at Knoll Gardens in Dorset where in pots it survives temperatures colder than -8°C (18°F) in winter.
This simple but highly effective planting of palms and drought-resistant grasses in Las Vegas, Nevada clearly demonstrates that aesthetics and utility can be combined to create harmonious partnerships.
All fountain grasses, members of the Pennisetum family, revel in hot, high-sunshine areas to the extent that all demand excellent drainage and sun to grow successfully in gardens. Although the seeding potential of some such as Pennisetum setaceum is an issue in sensitive areas, there are some excellent gardenworthy forms for easy use in all other areas. Pinks and whites are the flower colours favoured by fountain grasses, and produced in such profusion it is difficult not to be impressed by them. With one or two exceptions, such as P. ×advena ‘Rubrum’ whose purple foliage and long arching flowers are exquisite but only hardy in warmer areas, the foliage of fountains is not very exciting. Pennisetum villosum has large, fluffy caterpillar-like white flowers that literally cascade down the light green foliage when in full flower, amply demonstrating how the common name arose. Although perhaps the least hardy of the commonly grown fountains, it will grow in most areas as long as it has excellent drainage. Pennisetum orientale has a little less vigour but produces a large number of delicate pink flowers in a noticeably rounded outline and is the parent of several different very worthwhile hybrids and cultivars such as the rather taller and upright P. o. ‘Karley Rose’, whose flowers are a comparatively strong pink, and P. o. ‘Shogun’ with slightly softer pink flowers set off perfectly by the grey-green leaves.
When used close to buildings, large, simple blocks of grasses offer lightness and movement in clear contrast to impassive solidity. At a shopping mall in Las Vegas, Pennisetum ‘Fairy Tails’ provides an almost perfect antidote to the overabundance of hard surfaces.
Urban conditions, with a high percentage of paving and other hard surfaces, create ‘heat islands’ that reflect light and heat while repelling water, and can be very harsh on plants, especially in warmer climates. Fountain grasses such as Pennisetum ×advena ‘Rubrum’ are better adapted to such extremes and make excellent practical choices under such conditions.
Pennisetum alopecuroides has given rise to many very worthwhile garden cultivars, so that while the species itself can produce poor levels of flower in cooler and more maritime climates the cultivars will perform admirably on sunny, well-drained soils. Pennisetum alopecuroides ‘Hameln’ is perhaps one of the oldest but very useful for its distinct rounded outline of foliage that is quite literally covered in smaller but generously produced flowers. Pennisetum alopecuroides ‘Red Head’ is a recent form that has large dark flowers that are initially quite red at first while Pennisetum ‘Dark Desire’ has amazingly large dark to almost-black cylindrical heads of flower that demand attention.
While aridity and dryness are major limiting factors in warm climates, those areas which have the benefit of higher rainfall and cooler summer temperatures may regard such limitations as advantages. Dry, well-drained soils that provide comparatively dry conditions for roots during an otherwise wet and cold winter period will frequently make the difference between success and failure for many plants, including sun-loving grasses that are accustomed to warmer, drier environments. Bouteloua, Bothriochloa, Eragrostis, Jarava, Muhlenbergia, Pennisetum and Stipa are just some of the grasses that revel in relatively hot dry and sunny conditions but can be grown successfully in cooler, more mild climates if given full sun exposure and well-drained soils.
These brown grasses are in fact sedges, Carex species, that have a relatively short life span, at least under garden conditions. At the frequently dry and windswept RHS Garden Hyde Hall in Essex, England, the originally planted Carex comans specimens have long since died, to be replaced by seedlings that have been allowed to gradually colonize, creating this satisfyingly natural-looking planting.
For example, although the garden at Knoll is in southern England it forms part of a local frost pocket, with poor air drainage—and at just 20 metres (60 ft.) above sea level, it will record temperatures at least as low as -12°C (10°F) each winter. However, as the garden consists almost exclusively of a very fine sandy soil, most of the soil and therefore the plants’ roots are comparatively dry during these low temperatures. A combination of moisture and low temperatures causes the majority of damage to plants, so having a soil that remains comparatively dry during the winter allows us to grow many plants including grasses that might not otherwise survive. We can therefore enjoy the bright pink flowers of Bothriochloa bladhii, the amazing cascade of narrow flower spikes from Muhlenbergia rigens, the gold, braid-like nodding flowers of the unequalled Miscanthus nepalensis and the simply stunning masses of white flowers produced by Jarava ichu (formerly Stipa ichu) with only the occasional losses in more exceptional circumstances.
At Knoll Gardens, the gravel garden is sited on dry sandy soil that is frequently short of moisture, allowing dry-loving grasses like Pennisetum macrourum (front left), Muhlenbergia rigens (centre) and Miscanthus nepalensis (far right) to thrive. Photograph courtesy of Dianna Jazwinski.
Gravel can be a practical, effective and longlasting substitute for lawn grass, especially useful in areas where the amount of water used to maintain such a sward would be considered environmentally unsound. The shaggy outline of groups of deer grass, Muhlenbergia rigens, provides a fine contrast in shape and form to the relative flatness of the surrounding surface, even before flowering begins.
In heavier soils the addition of grit and gravels is often recommended to open up and improve the drainage and to help dry out the soil. However, a far more satisfactory technique is to raise the planting area by adding soil and organic matter, or to reshape and re-grade, to provide a planting area that is at least 15 cm (6 in.) or so above the surrounding area. This will allow the moisture to drain away from the roots and crowns of the plants which will considerably enhance the chances of successful cultivation.
Gravel gardens are popular and practical in dry areas that are mostly open to full sun. On a basic level they consist of a decorative layer of gravel, or other similar natural stone material, extended to cover the surface of an area through which plants are grown. The depth can vary from 2.5 to 7.5 cm (1–3 in.) and it works well on relatively large areas as a cost-effective substitute for high-maintenence turf grass or other high-water-use plantings. Using an ornamental finish in this way can allow for greater spacing between individuals and groups of plants than would otherwise be acceptable.
Beth Chatto’s Gravel Garden in Essex, England combines aesthetics with horticultural experiment. In an already low-rainfall area, and on dry gravelly soils, this area is never irrigated; the chosen plants must survive whatever the prevailing weather conditions offer. Reed, hair, oat and silver spear grasses all appear to thrive in the testing conditions.
On another level, gravel gardens combine free-draining soils, full sun exposure and low rainfall with drought-tolerant plants, drawing inspiration from naturally occurring drought-prone communities. For example, Beth Chatto’s famous Gravel Garden in Essex, England is described as a horticultural experiment; based on dry, poor soils in an already dry, low-rainfall area, the plants have been chosen for their ability to withstand prolonged periods of drought as this part of the garden is never watered. Even in these very dry conditions, Achnatherum calamagrostis (formerly Stipa calamagrostis), Stipa gigantea, Nassella tenuissima and even Calamagrostis such as C. ×acutiflora ‘Karl Foerster’ all thrive—and are arguably at their best when conditions are driest.
Attention to the surface detail can add greatly to the aesthetic value of the mulch. While evenly sized gravel is most common, using different sizes of material, from small thimble sizes through to comparatively large boulders, creates an extra level of interest. The use of locally sourced materials can add significantly to the sense of place, helping to relate the garden to the surrounding wider environment. A further refinement of this style involves the use of reclaimed materials such as crushed brick or rubble, which provide an excellent foil for plants as well as serving as a practical mulch while also re-using existing materials.
Summer dormancy in arid climates is an entirely natural response to prevailing conditions, just as winter dormancy is in colder areas. While summer dormancy is perhaps something of an acquired taste for gardeners accustomed to greener summer landscapes, it is an acceptable aesthetic in its own right. Allowing grasses and other plants to follow their customary natural pattern under garden situations offers a more genuine approach to truly sustainable gardening that links the right plant with the right place. The Strybing Arboretum in San Francisco, and the Leaning Pine Arboretum in San Luis Obispo, both in California, maintain good summer-dormant gardens that are as aesthetically pleasing in the height of summer as they are during any other season.
Under controlled garden conditions water is frequently available through irrigation, though the indiscriminate use of this finite and precious resource is increasingly, and correctly, coming into question. Even under the most arid of conditions, using drought-adapted grasses can significantly reduce the quantity and regularity of additional water that is needed to keep the plants alive. Embracing summer dormancy as an acceptable, even desirable, aesthetic in areas where it is a natural occurrence seems a highly sensible way to conserve water in places where it is already most precious.
In a meadow setting at the San Francisco Botanical Society’s Garden in the Strybing Arboretum, a collection of native grasses clearly demonstrates the beauty and utility of summer dormancy in mediterranean climates. Photograph courtesy of Dave Fross.
Truly summer-dormant grasses, such as the needle grasses, Nassella, can find it hard to adapt to conditions where a plentiful supply of water avoids the necessity of a summer closedown. Nassella cernua, N. lepida and N. pulchra are all exceptionally beautiful when in green and active growth but offer just as much, if in a more restrained way, in their dried state. For such highly adapted grasses, excessive summer moisture can indeed have deadly consequences. Contrastingly plants like the alkali sacaton, Sporobolus airoides, are quite beautiful if allowed to go into summer dormancy but can also tolerate summer water quite easily, so that they can be used along with other plants that require some summer water.
Nassella tenuissima (formerly Stipa tenuissima) is a quick-growing, easy-to-please evergreen producing dense heads of beige flowers and revelling in dry sunny conditions. Moving in the slightest breeze, especially when in full flower, it is perfect for this public park planting in frequently windy San Francisco.
Shade is not the natural setting for most true grasses. Yet shade is found in just about every garden, with dry shade in particular widely regarded as the most difficult of the cultural conditions under which to plant successfully.
True grasses, which mostly have their origins in open sunlit areas, are generally least able to cope with the shady conditions found in gardens, though there are a few notable exceptions such as the wild oat or spangle grass, Chasmanthium latifolium. Occurring naturally in shady woodland areas, it translates easily into a wide range of shady garden situations, making it a valuable exception to the general rule. It is also a really first-class garden plant whose wiry upright stems support thin green leaves that are in turn topped by very flat spangle-shaped heads of flower. Wild oat has real character and is a great addition to any shady planting area.
What will actually grow where depends very much on how much light is available. While it is fairly certain that confirmed sun-worshippers such as Pennisetum and Eragrostis are unlikely to approve of anything but full sun, the light levels encountered in, say, mediterranean areas will allow a greater tolerance from a larger number of grasses than would be possible in colder and less sunny climates. For example in the comparatively warm and dry climate of Arroyo Grande, California, in the garden of Dave and Rainie Fross, sun-loving Helictotrichon sempervirens along with other blue-foliaged grasses can be found happily ensconced in still very dry, but also far more shady, conditions than it could possibly tolerate in areas of lower light and heat.
As a general rule shade is very much the province of the grass allies, those plants that are not botanically grasses but have a superficial resemblance in one way or another to the grass family. Generally characterized by comparatively compact evergreen foliage, as well as flowers that are outshone by this foliage, examples include Carex, Luzula, Ophiopogon and Juncus. The turf lilies (Ophiopogon) provide understated elegance wherever they are used, their neat evergreen foliage seemingly impervious to the amount of shade or the dryness of the soil.
Wild oat, Chasmanthium latifolium, is one of relatively few true grasses that come from woodland conditions. With wide light green leaves and an upright habit, producing masses of distinctive flattened flowers, it is much underused in gardens.
Sun-loving, drought-tolerant blue-foliaged grasses such as Helictotrichon sempervirens (below, in back on the left), festuca (below, middle left) and sesleria (below, front right) grow happily under the very dry and comparatively shady conditions found in the mediterranean-climate garden of Dave and Rainie Fross in Arroyo Grande, California.
In fairly dense shade the dwarf mondo grass, Ophiopogon japnicus ‘Minor’, gradually makes reliably close carpets of dark green foliage in effective contrast to the more solid stones, paving blocks and surrounding large-leaved hostas at Chanticleer Gardens in Pennsylvania.
Among the most popular of these grass-like plants is the black mondo grass, Ophiopogon planiscapus ‘Nigrescens’, which seems equally happy in sun or shade. Its foliage is about the closest to pure black you can get in the plant world and it has tiny bluish white flowers and occasional fruits nearly the same colour as the foliage. The best performer for shade is the more infrequently seen green form, Ophiopogon planiscapus, which has tighter clumps of foliage that hardly if ever need attention so that it comes as close to being maintenance-free as any plant can. Nearly ten years ago at Knoll, we planted narrow drifts of O. planiscapus at what was the edge of a large silver maple’s leaf canopy; the plants have grown and flourished in the dry rooty shade, and have yet to require any maintenance other than occasional raking of fallen leaves from the maple.
The gradually spreading, rather than mounding, habit of Carex morrowii ‘Ice Dance’ makes for practical and durable ground cover as part of a public planting in New York.
Carex, the sedges, are a particularly large and adaptable group. Some can be found growing successfully in most levels of shade, and in very wet to almost-dust-dry soils. Sedges have given rise to many different cultivars, especially variegated-leaved forms which along with the species have become almost indispensable to successful shade planting. Again at Knoll, in the dry shade under large established shrubs, Carex morrowii ‘Ice Dance’ has created a most satisfying cover of creamy-white-striped green leaves that appear entirely indifferent to the dryness and lack of sun. Other first-class selections include the long-established almost-white C. oshimensis ‘Evergold’ or the slightly finer leaved C. ‘Silver Sceptre’. In contrast, Carex divulsa has a plain green leaf but its neat rounded habit and ability to perform in a wide variety of environments places it firmly in the front rank.
Shade itself can come in many different forms. It ranges from the light, open shade of a fenceline or single-storey building, through more serious levels of shade and rain shadow in the lee of larger buildings and distant woody plants, to the severely limiting dry shade to be found under the canopies and within reach of the questing root systems of established trees.
The comparatively open shade cast by fences, buildings and other non-living objects is often easier to accommodate, as there are no root systems from large established trees or shrubs with which new plants have to contend. What’s more, while direct access to the sun may be physically denied, the surrounding area can still be relatively open so that light levels are frequently sufficient to sustain a wide range of plant growth. In such situations, not only will the shade-tolerant grasses and sedges such as Deschampsia, Molinia and Carex do well, but some of the main groups of grasses such as Miscanthus and Panicum may also find enough sunlight to thrive.
In fact, certain miscanthus may appear to be quite happy in a reasonable amount of shade. Miscanthus sinensis ‘Abundance’, for example, well-named for its enthusiastically produced masses of flower, grows well at Knoll in the shade of larger shrubs, and while not cut off entirely from any direct sunshine it contends successfully with dry soils and other established root systems. Miscanthus chosen for their foliage rather than flower also seem to cope pretty well with noticeable amounts of shade. Elsewhere in the garden Miscanthus sinensis var. condensatus ‘Cosmopolitan’, with its wide healthy green-and-white leaves, has been growing in the shade of trees and bamboo for some years and while perhaps not as large or exhuberant as when grown in easier conditions appears quite tolerant of these challenges. Miscanthus sinensis ‘Dixieland’, M. s. ‘Variegatus’ and even the striking M. s. var. condensatus ‘Cabaret’ seem to cope remarkably well in various degrees of shade.
This restful waterside planting of Carex oshimensis ‘Evergold’ at the RHS Garden Wisley in England makes full use of the cultivar’s mounding habit. The surrounding woody plants will gradually create more shade. Black mondo grass, Ophiopogon planiscapus ‘Nigrescens’, and Tanorange Carex testacea complete the ground pattern.
Heavy shade cast by established trees and shrubs is the most difficult in which to plant successfully, whether with grasses or any other group of plants. This is because the lack of light is combined with extreme dryness at the root, usually at a time when moisture is needed during the active growing period.
Under deciduous trees and shrubs there can often be adequate moisture in the spring period, after the winter rains occur and before the trees leaf out. Spring-flowering bulbs take advantage of this period to flower and then close down as the tree wakes up and the soil starts to dry out. Several grasses have copied this strategy, including the wood melics (Melica) and the wood millets (Milium), which are at their best before the dry summer period when they close down until the return of wetter winter conditions. Among the most useful spring-flowerers is the snowy woodrush, Luzula nivea, whose tight mounds of green leaves, covered in soft white hairs, are topped by the most subtly beautiful spikes of white or off-white flowers, at their best before soils become too dry. Amazingly adaptable, this woodrush will grow in most types of shade from almost-boggy to fairly dry.
Most miscanthus flower best when sunlight levels are sufficient to stimulate effective blooming, but foliage forms, which are not grown primarily for their flowers, can tolerate more shade. Miscanthus sinensis ‘Abundance’ produces masses of flowers but appears tolerant of this semi-shady position at Knoll Gardens.
Where tree roots have not entirely taken over the soil, or under younger, less established trees or shrubs, the hakone grasses, Hakonechloa macra and its cultivars, can make wonderful longlasting mounds of delicate-looking foliage—a constant delight. Initially somewhat slow-growing, they are very long lived and durable once established. At Knoll one of the most satisfying of all combinations has resulted from planting Hakonechloa macra ‘Aureola’ (‘Alboaurea’) in a 3–4-metre (9–12-ft.) circle around the base of a paperbark mulberry. While not in the deepest of shade, the sandy soil and roots of the mulberry ensure frequent dryness during the summer months, which the hakone grass simply shrugs off. The combination of the grass’ and bark’s textural qualities with the tree’s leaves is as immensely satisfying as it is undemanding to maintain.
Luzula nivea, or snowy woodrush, is a rosette-forming plant producing masses of white flowers early in the season. Happiest where soil is not too dry, the common name refers to the silvery hair that can be seen on younger leaves.
For conditions ranging from full sun to the driest of shade, the pheasant grass, Anemanthele lessoniana (formerly Stipa arundinacea), is perhaps the most adaptable and successful of grasses—being not only very tough but also very beautiful and quick growing. Even close to large evergreens such as conifers, which offer perhaps the harshest and most unrelenting of dry shade, the pheasant grass is among the likeliest of candidates to survive and prosper.
Hakone grasses do well in or a reasonable amount of shade. At the base of a paperback mulberry, Hakonechloa macra ‘Aureola’ makes graceful, weed-proof and longlasting cover in dry, light shade at Knoll Gardens. Photograph courtesy of Dianna Jazwinski.
Pheasant grass may be the most adaptable grass for all levels of shade (except in combination with wet soils). Anemanthele lessoniana is fast growing, with wider-than-high mounds of of evergreen leaves that continuously change from reds and oranges to greens and yellows. In the Fross garden in California, these well-spaced plants cope admirably with very dry, shady conditions.
For rather wetter conditions in shade, the purple moor grass and tufted hair grass, Molinia and Deschampsia respectively, both occur naturally in wetter soils, and even at the water’s edge, in open conditions or where shade is not too dense. Tolerant of even more shade along with wetter soils are a large number of sedges, such as the architectural Carex muskingumensis, and woodrushes which thrive in the seasonal variations of flood and drought that these particular areas frequently face. By and large the woodrushes are not the most attention-grabbing of plants, but their ability to tolerate damp, wet conditions in shade makes them most useful for covering areas that other plants might find testing. Luzula sylvatica, for example, creates rosettes of green leaves that are truthfully not very exciting, and the variegated form L. s. ‘Marginata’ is scarcely better, but their ability to cover ground in tough conditions is almost unmatched. The golden form L. s. ‘Aurea’ is perhaps the exception; in spring, its bright golden yellow foliage can light up the darkest of corners. (This form should not be sited in full sun as it is inclined to scorch if too hot.)
Most true grasses do not appreciate wet, boggy, watery conditions.
The very demanding nature of some of the more watery environments has given rise to a specialized group of plants whose specific qualities have not always been appreciated by gardeners. In nature the area where the land meets the water, also known as the transition zone, is in many ways a unique habitat. A brief look at any estuary or river mouth will show a mix of habitat from sandy beaches to boggy soils, along with marshland and plants that have adapted to cope with these conditions as well as a whole ecosystem of associated wildlife that has evolved to thrive there. Often in a state of permanent flux with the regular and sometimes rapid changing of water levels in times of flood or drought, the plants that have adapted to these marginal areas are mostly grass allies such as sedges, rushes and reeds.
Comparatively few true grasses have adapted to really wet environments, though the so-called common reed, Phragmites australis, is one very notable exception, covering vast areas of land and water’s edge with equal facility. Like the common reed, all such truly adapted grasses, and some grass-like plants such as Glyceria, Juncus and Schoenoplectus, have a running rootstock that can move swiftly in order to survive in the constantly changing conditions of their natural homes. However this strategy can make them less than welcome in the more controlled conditions of the average garden unless they are used in very wet conditions such as stream sides, boggy areas or lakes and ponds.
For practical purposes, grasses that can tolerate wet soils, which are usually around or in proximity to water, could be placed in one of two broad categories: those that prefer to paddle and those that don’t mind swimming. Paddlers are those grasses that are able to thrive with a fair amount of moisture in the ground for extended periods. While they will tolerate heavy clays that are often waterlogged, on the whole they prefer solid ground. Swimmers, on the other hand, will be happy in permanently wet to open water conditions. By definition most swimmers also make happy, if enthusiastic, paddlers.
Most sedges such as Carex muskingumensis, cotton grasses such as Eriophorum angustifolium, woodrushes such as Luzula sylvatica, and the purple moor grass, Molinia caerulea, are paddlers. They are at home in a range of soil conditions from sometimes-dry to damp to wet to water-logged, but still grow primarily in soil rather than water.
Vast areas of river mouth, wetlands, lakes, open water and estuary play host to a relatively small number of species, such as reeds and rushes, which thrive in wet, stagnant to fast-flowing conditions that are permanently in limbo, somewhere between solid ground and open water.
Given the wide range of tolerance and adaptability that many grasses display, it is also quite possible to find specimens of the main groups of true grasses such as Miscanthus and Panicum growing in very wet soils, including heavy clay, even right up to the edge of open water. However, a grass is usually most tolerant in its native area and may consequently be less forgiving when used as an exotic in a garden or designed space. For example, the prairie switch grass, Panicum virgatum, is tolerant of wet conditions, and can even be found growing with its feet in water in the New Jersey Pine Barrens where it is locally native, but is unlikely to be as tolerant in the maritime conditions of the U.K.
Common cotton grass, Eriophorum angustifolium, thrives in the open yet boggy conditions of a nature reserve a short distance across open water from the busy urban centre of Poole, Dorset, England.
In the inspirational gardens of Beth Chatto at Elmstead Market in England, the waterside plantings include not only Carex elata ‘Aurea’ and Molinia caerulea subsp. caerulea ‘Variegata’, which are native and happy alongside or even in the water, but also Miscanthus sinensis ‘Zebrinus’. Planted just a little further away from the water’s edge, the miscanthus will no doubt be able to draw on the relatively high water table and also cope perhaps with an occasional flooding, but nonetheless remains for the most part on comparatively solid ground.
The swimmers include reeds and rushes such as Juncus, Phragmites, Typha and Schoenoplectus whose strong, mobile root systems are equally at home in solid ground but have evolved to deal successfully with the shifting ground, or lack of it, in a watery environment. Their ability to travel over such a variety of conditions gives many coastal and lake-side areas their characteristic look and feel and is the prime reason for their successful and increasing use in stabilization and erosion control projects. While some such as Phragmites, even in its comparatively restrained variegated form P. australis subsp. australis ‘Variegatus’, may not be suitable for the smallest garden areas, several make the perfect accent in ponds and smaller water features, including those with comparatively restrained ornamental forms such as Schoenoplectus lacustris subsp. tabernaemontani ‘Albescens’ with its unique light green and cream longitudinal stripes on brittle rounded stems. For a more bulky but still controllable plant, the attractively variegated Spartina pectinata ‘Aureomarginata’ is a good choice to associate with other moisture-loving perennials such as Eupatorium, Lythrum and Filipendula.
Panicum virgatum, the prairie switch grass, tolerates wide-ranging conditions from drought to water’s edge where its stout root system can help to prevent erosion, as seen on the lake edge at Chicago Botanic Garden.
This masterful planting in Beth Chatto’s renowned gardens in Essex, England uses Miscanthus sinensis ‘Zebrinus’ (centre left), Carex elata ‘Aurea’ (centre) and Molinia caerulea subsp. caerulea ‘Variegata’ (far right) in successful association with larger-leaved plants such as the giant rhubarb, Gunnera tinctoria, which are happy in the usually damp soils at the water’s edge.
Several moisture-lovers such as Juncus, Luzula and various species and cultivars of Carex are recommended for being able to cope with rather dry and shady conditions, which initially appears as something of a contradiction considering their native habitats. But most wet soils, whether by open water, pure heavy soils or open boggy moorland, can become drier (and sometimes even dry out completely) as part of an annual cycle, and as a result many damp-loving plants have had to adapt to deal with such periods of relative drought. Sedges in particular are very adept at this; many species such as Carex divulsa, C. remota, C. praegracilis, C. elata and C. obnupta can tolerate relatively dry soils provided they receive the occasional long drink from rainfall or irrigation.
Used historically for matting and thatching, the common club rush, Schoenoplectus lacustris subsp. tabernaemontani, makes dense colonies in rivers and open water, providing cover and forage for wildlife as well as an ornamental feature for the local human population in Wimborne, Dorset, England.
Carex secta, a graceful sedge from New Zealand, grows happily in the boggy water-logged soil introduced into a man-made pond at Knoll Gardens.
Where no natural water exists, introducing it into the designed space can result in a hard and frequently unsympathetic margin between the water and the rest of the garden. Swimming pools and formal ponds are common culprits, so often appearing as afterthoughts that are almost completely disconnected from the rest of the garden design.
Planting grasses close to such features, at least on one side, helps to soften the demarcation between water and ground, linking the water feature with the rest of the garden. Where the soil conditions are not affected by the water’s proximity, choose any grasses that can cope with the prevailing soil conditions, which may be quite ordinary to dry. Sun-loving grasses such as the fountain grasses or Pennisetum species, for example, can be superb at gracing the surrounding areas of a garden pool, where their rounded outline and bottlebrush-like flowers contrast with, and are often mirrored in, the flatness of the water’s surface. Miscanthus sinensis ‘Morning Light’ is another excellent choice, with a clear vase-like outline that stands out particularly effectively against a background of open water.
One simple but highly effective water feature for gardens with no natural water is a ‘low-tech’ sloping-sided pond. With no clear division between the water and the surrounding soil, this type of pool allows for the development of a transition zone in which many of the more gardenworthy moisture-lovers such as star sedge, Rhynchospora, and cotton grass, Eriophorum, can be grown. Sited in a lower part of the garden, lined if desired, not necessarily too deep and requiring no special attention in the form of filtering or cleaning, such ponds always seem to attract wildlife. They are easy to maintain and constantly interesting.
Where a steep-sided, more formal pond is already in existence, it can be quite easily converted to make a whole new planting habitat in an otherwise dry garden. For example, at Knoll we had a formal rectangular pond only about 45 cm (18 in.) deep, with brick sides and a base of butyl liner. Hard paving surrounded more than half of its perimeter, the rest being border, and there was no filtration. With water that turned green in warm weather, the feature left much to be desired—in fact, it seemed rather pointless.
But as the garden consisted almost entirely of dry sand with very little moisture, this outdated water feature offered a perfect opportunity to create a self-sustaining watery habitat that was otherwise absent from the garden. Sandy soil, not too rich in nutrients, was simply barrowed directly into the pond in sufficient quantities to make small islands of soil that appeared just above the usual level of the water after settling, leaving about half of the pond as open water.
Moisture-lovers that now excel in the boggy soils include the lesser bulrush, Typha angustifolia, while Molinia caerulea subsp. arundinacea and even Arundo donax ‘Macrophylla’ rub shoulders with Eupatorium lindleyanum and Eupatorium maculatum Atropurpureum Group. Juncus effusus has seeded in the shady corners next to the distinctive foliage of Carex muskingumensis, and the delicate and longlasting star sedge, Rhynchospora latifolia, displays its incredible white flowers close to the paving. Carex elata ‘Aurea’, always distinctive in ordinary soils with its golden yellow leaves topped with yellow and black flowers in late spring, is even more robust and obviously very happy. Carex secta, a subtly beautiful evergreen sedge from New Zealand, has meanwhile developed into a huge ball-shaped specimen that simply demands admiration the moment it is seen. Apart from some annual tidying, this area has required virtually no attention—at least, not from the gardener; it gets much attention from myriad forms of life including frogs, toads, dragon flies and damsel flies, grass snakes and slow worms.
Easy to grow on the whole, grasses are no less obliging when grown in containers provided their basic needs such as water, light and adequate root run are met. Indeed, for many gardeners some of the slower-to-establish grasses perform better in pots than in open ground, at least in their early years. One example is the Japanese blood grass, Imperata cylindrica ‘Rubra’, which can be very slow to establish in the open ground; in its native Japan it has been grown for many decades in shallow dishes as a companion to bonsai.
In many respects, container-grown grasses demand the same considerations as other container-grown plants. Drought-loving grasses will (unsurprisingly) tolerate less water than moisture-lovers, and those slower growers like the hakone grass, Hakonechloa macra and its forms, will survive happily for longer without being re-potted. However, attention to irrigation, pot size and growing medium is necessary for successful container growing.
Some grasses that are grown primarily for their foliage are especially effective in taller containers, as this allows the foliage to gradually trail downwards and develop a more pendulous habit than the grasses would manage when planted in the ground. For example, the purple-tinged foliage of Eragrostis curvula ‘Totnes Burgundy’ deepens in colour as the season progresses and if grown in a sufficiently tall container it gradually develops a distinct weeping habit that is quite special. The flowers of this wonderful form, especially when grown in pots, can distract from the foliage and are often best removed for maximum impact.
Certain evergreen sedges can also develop this habit. For instance, the tan-coloured leaves of Carex testacea seem to extend much further than their normal length when given the opportunity. And while in open ground the flowers of C. testacea and of other species such as C. dipsacea are usually insignificant, passing virtually unnoticed, in a tall container they appear to adopt the same extended weeping habit as the leaves; at Knoll we have seen them extend to well over 1 metre (3 ft.) long, making a quite spectacular display.
A collection of plants in containers, whether entirely grasses or a mix of plants in differing shapes and sizes, can make for a very satisfying display in a relatively limited space over a long period of time. Individual containers can be rearranged or replaced, allowing for a constantly changing matrix of flower and form to delight and refresh the senses.
Grasses which are borderline, or distinctly non-hardy for the area where they are being grown, can be more easily protected from frost when grown in containers that can be moved at short notice so that plants are kept warm and/or dry as required during the colder months. For example, Pennisetum ×advena ‘Rubrum’ and Cyperus papyrus are two architectural but non-hardy grasses that can be grown successfully in cooler climates using containers.
On hard surfaces like terraces close to the house, or where soil or space is lacking such as on roof gardens or balconies, the thoughtful use of containers is a successful way of providing a home for plants. And with a little ingenuity, as much interest can be gained from the containers as from the plants themselves. Whether of horticultural origin or not, any suitable receptacle can be pressed into service as long as it will hold the growing medium (compost) and allows water to drain. However, it is genuinely true that the more capacious the container, the longer and better the plant will grow.
Grasses need not always be planted in the pots to make an effective association with containers. The clever placing of a single empty pot at Chanticleer in Pennsylvania uses the relatively solid shape of the container in effective contrast to the effervescent outline of nearby groups of Panicum virgatum.
The strong linear outline of most grasses contrasts effectively with more solid objects, especially when made of natural materials such as terracotta and wood. The association is no less effective during the quieter winter period.
Containers made of wood, stone or other natural material usually make the most satisfying associations with plants, and this is particularly so with the strong linear outline of grasses. The simpler geometric outlines of circles and squares combined with finishes that develop an ever-changing patina with increasing age, such as rusty metal, may provide the greatest satisfaction in terms of contrast between plant and container.
A tall, elegant container allows Carex testacea to display bronzed evergreen foliage that appears to gradually creep ever downwards—a trait that would be lost were it planted at ground level.
Most grasses with fibrous root systems are happy in containers, provided they are watered when dry and re-potted when necessary. Containers also allow you to grow plants that would be considered at risk if grown in the open ground in certain areas, such as Jarava ichu which forms part of the entrance container display at Knoll Gardens.
Magnificent stone urns at the end of the famous canal at the RHS Garden Wisley in Surrey, England provide a perfect traditional setting for the distinctive outline of Miscanthus sinensis ‘Morning Light’.
