Plants are increasingly being recognized as a vital part of our urban and domestic environments, not just a luxury or an unnecessary – if pleasant – bit of decoration. It has long been established, for example, that the mere view of plants through a window has a beneficial effect on the human psyche, and that plants can play an important role in cleaning and purifying the air of buildings and built-up environments.
Gardening, whether on the most intimate private level or the most extensive and public, involves an appreciation of and involvement with the natural world. For many people, plants may be their only point of contact with nature apart from feeling the effects of the weather. Private gardens offer the opportunity for personal choices to be made about what plants to grow and how to manage them, while designers of civic landscapes have always had the responsibility of serving the wider public interest. There is, however, a new and additional agenda for gardeners, both private and public: sustainability and the support of biodiversity. Sustainability demands that we minimize irreplaceable inputs in gardening and reduce harmful outputs, while the support of biodiversity brings a demand for wildlife-friendly planting and practices.
The use of long-lived perennials in conjunction with woody plants – the approach Piet Oudolf and I, Noel Kingsbury, have always supported – genuinely offers improved sustainability and support for biodiversity. Reducing the amount of regularly mown lawn and the unnecessary trimming of woody plants for unclear motives is surely a step forward. Creating rich garden habitats offers natural beauty close at hand, provides resources and homes for wildlife, and improves the sustainability of management.
Deciding what plants to use and how to arrange them is covered by the field of planting design, which brings together a combination of technical knowledge and artistic vision. This book looks at some of the recent trends within planting design, and is aimed primarily at home gardeners, garden design and maintenance professionals, and landscape architects. It has important lessons for others, such as architects, who do not use plants directly but often have to situate their work in close proximity to them, or ecologists, whose profession does not involve much design but who increasingly have a role to play in the creation and management of designed plantings.
While the role of plants – and therefore planting design – is well established in the domestic garden, and is indeed absolutely crucial to its aesthetic and functional success, it has not been so well established in landscape design. Or perhaps more accurately, plants have often played a minor role in urban landscape design. Historically, for centuries the only plants used in cities were avenue trees; the nineteenth century saw the growth of urban parks, the late twentieth a much wider use of plants in urban areas – a practice to a large extent pioneered in the Netherlands. Now, however, the use of plants is increasing, particularly that of perennials and ornamental grasses, requiring greater access to technical information about plant establishment and management, and to ideas about the visual aspects of their use. It is perhaps worth looking at these new trends.
The former nursery at Piet and Anja Oudolf’s at Hummelo in the Netherlands. It is now a boldly experimental area where robust perennials grow amidst a sown mix of wild pasture grasses along with various spontaneously arriving species. Only time will tell how it will work out. The pale mauve-blue is Aster ‘Little Carlow’, the dark red Eupatorium maculatum ‘Riesenschirm’.
A randomized perennial mix designed by Nigel Dunnett at Sandvik Tools, Warwickshire (2007), designed to capture and hold water during periods of high rainfall and so prevent flooding. The dark purple is Aster novi-belgii ‘Purple Dome’.
While green roofs have captured the public imagination, the technology involved in their construction is also being used in many other situations, often not immediately recognisable as roofs. Increasingly, high-density urban environments are creating artificial growing situations which require soil or artificial soil-like substrates above impermeable surfaces. An example of such a green roof which is not a green roof might be Chicago’s Lurie Garden – built over a parking garage.
Green roofs are often categorized by the use to which they are put: extensive roofs are functional and usually have a shallow substrate; intensive are more likely to be roof gardens with conventional planting; semi-intensive ones are somewhere between and are developed for their visual appeal as well as functionality. Extensive and semi-intensive roofs tend to be planted up with plant ‘communities’ – combinations of plants selected for the conditions which coexist well and survive with minimal maintenance, often species from dry meadow habitats. In this sense there is a real distinction between these and conventional plantings, where plants are placed individually.
A major environmental problem in cities concerns the management of water, especially the control of excessive run-off during storms, which can cause flooding and associated pollution. Sustainable urban drainage schemes (SUDS) are designed to capture water, and either store it or release it slowly into the water table or streams or allow it to be evaporated back into the atmosphere. Domestic gardeners in some cities are encouraged to develop rain gardens where the same objectives are reached, with no drainage water leaving the property and the minimum amount of irrigation water brought in. Green roofs, with their capacity to store rain as it lands, often play a role in integrated SUDS. SUDS often involve swales – detention basins where water can be held temporarily before slow release into natural drainage systems. Often these are planted up with a carefully selected vegetation, usually locally native species which can survive periodic inundation but dry conditions too. More ornamental planting combinations are, however, also possible. Again, the emphasis is on mixtures of species.
This swale, designed by Nigel Dunnett for London’s Olympic Park, illustrates well a basic concept of sustainable drainage schemes. Drainage water is collected in the lowest part of the site and allowed to drain slowly into the water table, with only the excess being taken off site. A diverse community of British native plant species are used; clearly visible are white Leucanthemum vulgare and pink Lythrum salicaria.
Biofiltration is the reduction of polluting chemicals in the environment through the use of plants. Street trees, green roofs and living walls are all examples of plant life which can be effective at trapping dust, and breaking down complex hydrocarbons (often known as Volatile Organic Compounds – VOCs) into harmless CO2 and water. Plants differ in their ability to break down specific VOCs, so combinations are often more effective than just one species.
A more targeted biofiltration technique is in the idea of the natural swimming pool, developed in Germany, where plants act in conjunction with beneficial bacteria to break down or trap nitrogen and phosphorus compounds, so denying nutrients to disease-causing bacteria. The plants used are often grown as a mixed community, as different species have different roles to play in a complex set of biochemical reactions.
Post-industrial societies often leave behind large areas of wasteland: abandoned industrial facilities, railways, mines, military training grounds and the like. These are often overrun with plants with remarkable speed, bringing home to us very forcefully how rapidly and thoroughly nature can recover lost ground and heal polluted and damaged environments. Such places often develop a fascinating and unique flora, a combination of locally native species, weeds and escaped garden plants. So often ‘redevelopment’ means the destruction of these unique plant communities. Recent years have seen a more positive interpretation of these places; led by Germany, areas of post-industrial wasteland are being managed more respectfully and creatively to preserve something of their special character.
One of the most famous examples of such plant conquest of abandoned land is the New York City High Line, an elevated freight railway line last used in the 1960s. The last part of the line was closed in 1980. Its redevelopment as a park had to involve complete rebuilding so the flora was lost, but Piet Oudolf’s collaboration with landscape architects James Corner Field Operations is intended to evoke the wild feeling of the old High Line. The remarkable success of the project is now inspiring other projects in the USA, and highlighting the importance of post-industrial landscapes.
What is striking about many of these new and distinctly technological and engineering approaches to planting is that communities of multiple species are being used – relatively stable groups of plants which can be managed altogether as a unit. This is part of the zeitgeist of contemporary planting design – a slow move away from precise individual plant placement to combinations of species, designing and planting something which is greater than the sum of the parts, developing a vegetation rather than planting a mass of individuals.
Key to the idea of combinations of plants is the intermingling, mixing or blending of species, as opposed to the use of blocks or groups. This creates an effect which is visually more complex and naturalistic. This also means that there is more interaction between plants, and so more competition – as a consequence there is a need for a greater knowledge of ecological issues or at least a greater awareness of long-term performance.
This book aims to explore the new emerging planting design based on intermingling combinations. It is centered around the work of Piet Oudolf, a Dutch landscape designer who works on private and public commissions in northern Europe and North America. It also includes some material about other practitioners working with plant combinations in several different countries: landscape architects, academic researchers and public space managers. I – Noel Kingsbury – have written the text, but this has been very much a joint project between Piet and myself, so for most of this book I am writing on behalf of both of us. Chapter four, ‘Long-term Plant Performance’, however, has been the result of research as part of a doctoral thesis with the Department of Landscape at Sheffield University followed by some further formal research work; consequently, I have written this with my voice.
What unites the two of us is our passion for and close involvement with plants. Just as the best potters have an intuitive understanding of clays and glazes and master cabinet makers a deep feeling for every type of wood they use, skilled planting designers have a knowledge of the plants that make up their repertoire. Piet’s work as a designer is based on 35 years of not just using plants in designs but growing them himself and, from 1982 to 2010, running a nursery with his wife, Anja. I have a background in nursery work myself (albeit for a very much shorter period) – there is nothing like it for gaining an intimate knowledge of how plants behave, what they do and when they do it, and – crucially – what goes on underground: how roots behave. The knowledge needed to propagate plants and then grow them on is that of plant performance – such experience is then invaluable for understanding how they will perform over many years. This surely is a major part of the Oudolf success story.
It is helpful to think about the material in this book as covering two gradients: from macro to micro and from order to spontaneity. The first chapter, ‘Planting – The Big Picture’, looks at the context of plantings and the gradient from order to spontaneity. The second chapter, ‘Grouping Plants’, considers the middle level: how plants can be put together in different ways. This is very much about Piet’s work, for he is a true designer, in contrast to many professionals whose work is also featured in the book, who could perhaps be better described as ecological engineers. Piet’s plants are precisely placed, and indeed much of this chapter is given over to a study of his planting plans. Over time, his plants may move about – which is fine – but the intention is that such changes will only very slowly degrade the original design concept.
Chapter three, ‘Combining Plants’, comes down to a lower level, looking at combination and juxtaposition: why one plant looks good next to another, how combinations can be made to look good at particular times of year, why one grouping may change with time faster than another. I pay particular attention to plant ‘architecture’ – their shape and structure. This chapter will be of most interest and use to the new gardener or designer and to those with only small spaces. Chapter four on performance looks at issues crucial to the long-term survival and spread of perennial plants, but also at death and disappearance. Such issues are vital to understand, not just for the ongoing management of plantings but also at the planning stage.
A fifth chapter covers the work of others who are at the naturalistic cutting-edge in planting design. Whereas Piet’s work can be seen as an artistically stylised version of natural habitats, most other practitioners in the field are more concerned with a randomizing of individual plants from a carefully researched selection. The term ‘ecological engineers’ describes their approach, which combines a technical knowledge of plant performance with visual appeal to create relatively stable and highly decorative plant communities.
Garden and landscape making is increasingly becoming a globalized business. There was a time when the vast majority of ornamental or amenity plant growing happened in the cool temperate climates of north-west Europe, North America, their southerly Mediterranean climate fringes and Japan. Anything done beyond these areas tended to be quite ‘colonial’ and derivative in character. This is now changing. As the so-called emerging markets generate more resources for public and private garden making, immense new possibilities are opening up. One is for the ongoing development of garden traditions which became stalled – either through cultural decline or the impact of imperialism – notably Islamic, Chinese and Thai. Another is working with plant palettes which have never before been utilized in design.
This latter approach, the use of novel plants, is tremendously exciting. Much garden design in non-industrial or emerging economies in the past has used a limited flora, repeated all over the world across appropriate climate zones; the monotony of endlessly meeting bougainvilleas, yuccas and Ficus benjamina wherever you travel in the tropics is deeply disappointing. The garden, landscape and nursery professions are now increasingly turning to their own floras rather than this global lowest common denominator mix. The reasons are many: a desire to celebrate regional diversity, patriotism, a wish to support biodiversity, and a need for species which are guaranteed to survive the onslaught of difficult local climates.
One example illustrates how this process can work. Amalia Robredo is a garden designer who practices on the coast of Uruguay, an area with a number of interesting plant communities, now seriously endangered by development. Over the last few years she has systematically made herbarium specimens, got them identified by botanists at the University of Montevideo, collected seed, grown and trialled plants in her garden, persuaded local nurseries to start growing them, and then used them in projects. For a coastal climate, with frequent high-velocity and desiccating winds and sandy soils, the use of such plants makes sense, as well as replacing lost habitat and encouraging people locally to value their environment. For us there will be further advantages, as new species adaptable to other climates make their way into global commerce – not as in the past as species introduced directly from the wild, but already tried and tested by local nurseries and gardeners. Piet’s work in the United States and his collaboration with native plant specialists such as Roy Diblik of Northwind Perennials in Wisconsin have already contributed to a growing interest in North American perennials among garden and landscape professionals in central and northern Europe.
Practitioners in this field tend to be very collegiate. We swap ideas, images and plants. We may produce very different results but share many of the fundamental beliefs, which are also being increasingly shared by others beyond our field, both amateur and professional. We are all passionate about wild plants and wild plant communities, and about the need for gardeners and landscape professionals to create environments which support biodiversity as well as nourishing the human spirit. This book will inspire, encourage and enable others to join us.
We live in interesting times for planting design. There are a great many areas where the integration of plants with architecture and the wider urban fabric is taking plants beyond their merely ornamental or amenity use. Planting design has long been something of a ‘Cinderella’ within landscape design, and even in the booming profession of garden design it enjoys surprisingly little discussion. Now landscape architects and designers are paying it more attention, and with a growing acceptance of the need for plants to be woven more deeply into the fabric of our lives, I hope this book will make its contribution.
A spontaneous meadow garden at Carrie Furnace, Pittsburgh, Pennsylvania, with spikes of Echium vulgare particularly prominent. Post-industrial landscapes can be remarkably biodiverse and even beautiful. Landscape consultant Rick Darke is involved with managing this abandoned industrial area, describing his role as ‘to identify the useful components of the existing spontaneous vegetation on the site and ways of integrating this in the eventual designs . . . which will have the historic ironworks at the core of mixed-used residential, professional, retail and trailways development.’
The Salvia and Achillea planting at Hermannshof, Weinheim, in Germany’s Rhine Valley, is an example of a naturalistic planting designed for color and structure and to thrive on dry alkaline soils. The blue-purples are seedlings of Salvia nemorosa and S. ×superba cultivars, the blue a hybrid of Veronica longifolia. The tall yellow is Verbascum speciosum, a self-seeding biennial. In the foreground is grass Festuca mairei from the Atlas Mountains in north-west Africa, where the climate is similar to regions with steppe or short-grass prairie habitats.
Amalia Robredo in Uruguay is one of the pioneering plant-oriented designers using locally native species for the first time in their regions. The wild flora of the Uruguayan coast has many attractive plant species. Here the grass Andropogon lindmanii grows alongside silver Achyroline satureoides.
A green roof on the Uruguayan coast designed by Karina Hogg, with planting by Amalia Robredo uses a mix of native (recently introduced into cultivation) and non-native species. Conditions are extreme with salt spray and exposure; the substrate is 5–7 centimeters. The silver is a native sand dune species, Senecio crassiflorus; the yellow daisy is a rare local endemic, Grindelia orientalis; the blue is Plectranthus neochilus. The grass in the foreground is locally native Stipa filifolia.
With the High Line now so popular, many other communities are looking at abandoned rail lines as potential public spaces. Like many former industrial sites, their poor and sometimes polluted substrate, which hardly earns the name of ‘soil’, is actually very good for encouraging a wide range of plants; it is a counter-intuitive fact of ecology that stressful environments often support more species diversity than fertile ones. Here, in Reading, Pennsylvania, garden escapes Macleaya cordata and a species of Verbascum are prominent. In other locations rare natives may find a niche.
The design for New York City’s High Line was intended to evoke the spontaneous vegetation of the old abandoned railway line. Here, in October, are seedheads of the grass Sporobolus heterolepis and Eupatorium maculatum ‘Gateway’ alongside the yellow flowers of Rudbeckia subtomentosa.
Chicago’s Lurie Garden, part of the Millenium Park project, opened in 2004, is an example of a new kind of urban public garden. It is in fact a giant green roof, as it is built over a parking garage, yet reads as part of a ground-level landscape. Offering a stylized version of the Midwest prairie, its combination of native and introduced perennials and grasses is symbolic of a blend of nature and culture. Such a blend is easily understood by city dwellers, some of whom will be tempted to find out more about wildflowers and so be drawn into wider issues of conservation and biodiversity.
