A methodology for ecological landscape. and planting design—site planning and. spatial design

Darrel Morrison

The native landscape of the United States is richly diverse, both botanically and aesthetically. Tall-grass prairies with billowing waves of grasses and colourful wildflowers once covered millions of acres of the Midwest. Longleaf pine savannas with an incredibly rich ground layer of grasses, ferns and flowers blanketed some 92 million acres of the southeastern coastal plain. Majestic mixed forests of hardwoods and conifers covered much of the northeast; diverse desert vegetation grew in the arid southwest. Today, just tiny remnants of the presettlement landscape that have been protected by public agencies and private non-profit organisations, such as The Nature Conservancy, remain. These remnants remind us of our rich botanical heritage.

There has been, early in the twentieth century, and again for the last 25 years, an undercurrent within landscape design in the US which draws on these diverse natural plant communities for both inspiration and information. In the early twentieth century there was a movement to develop a landscape approach based on the native plant communities of the region. Jens Jensen was perhaps the most widely recognised practitioner of this approach. Born in Denmark in 1861, he emigrated to the US in his twenties, and practiced extensively in the Midwest from 1890 until his death in 1951. In the Chicago park system, and in a wide range of other public and private commissions, he became well known both for his masterful spatial designs and for his increasing reliance on the Midwestern prairies, savannas and forests as models for design. He was careful to clarify that his work was not copied from nature, but was inspired by it.

In 1929, Dr Edith Roberts and Elsa Rehmann co-authored a book entitled, American Plants for American Gardens. Dr Roberts, a plant ecologist, and Ms Rehmann, a landscape architect, taught at Vassar College, and in their book discussed how a variety of eastern US plant communities could be used as a basis for designing gardens and landscapes that would be distinctively ‘of the place’ and also ecologically sound.

Other landscape architects pursued similar approaches during the first three decades of the twentieth century. Then the economic depression of the 1930s, followed closely by the Second World War, contributed to a decline in this approach.

It was only after the first Earth Day celebration in 1970 that the concept of using native plant communities as a basis for design re-emerged as a sizeable undercurrent in American landscape architecture. That undercurrent has been strengthened, at least in parts of the country, as a response to environmental concerns, such as water shortages and the excessive use of chemicals and energy in maintaining mowed and manicured

landscapes. It is also reinforced by a desire to depart from predictable, generic landscapes that have destroyed regional uniqueness, and which are often aesthically dull.

Clearly, because of the presence—or dominance—of humans and human activities in the designed and managed landscape, it is unrealistic to believe that we can recreate a pre-settlement landscape over extensive areas. What we can do is to reconnect our designed landscapes with the natural heritage of the region and thereby begin to reinforce or restore regional landscape character. Further, the cumulative effect of many designed landscapes being based on the naturally evolved landscapes of the region can be a more ‘sustainable’ environment, less consumptive of water and energy resources than traditional ones; with the additional benefit of reintroducing many native species which have been eliminated from traditionally designed landscapes. Further, if a number of individual sites which are designed in this way are interconnected, they can begin to provide a network of ‘corridors’ through which wildlife can move.

In this chapter, we will discuss, first, traditional approaches to American landscape design as a basis for comparison with this alternative approach. Then, we will look at different degrees of departure from those current practices, in an effort to design more ecologically sound landscapes; and then we will look at a process that might be followed. Finally, a case study design project in the southeastern US Piedmont region will be presented. It should be noted that the emphasis in this chapter is on the use of native plant communities in landscape design, building upon the incredibly rich and underexploited resources that the US possesses in terms of its regionally distinct vegetation. This approach can be readily adapted for use elsewhere in the world, again drawing inspiration from appropriate native plant communities.

The use of native plant communities as a basis for a locally appropriate and distinctive landscape design provides a very strong underlying philosophy for plant selection. However, as discussed in Chapter 1, and in other chapters, naturalistic vegetation may, in certain contexts, include non-native species as well as native. This is perhaps most relevant in those regions where the native flora is limited (e. g. the UK, which has a much reduced native flora compared to continental Europe), or where cultural modification of the landscape has a far longer history than in the US. In these instances there may simply not be an appropriate native plant community type to provide for, say, a colourful flowering display in late summer in a prominent position in an urban park. The use of non-native species in ecological settings has been contentious (Chapter 1 discusses the issue in some depth), but in urban contexts the use of non-invasive exotic species in naturalistic vegetation can go some way to promoting a less resource-intensive public landscape whilst at the same time satisfying public demand for attractive plantings. The site-planning process described later in this chapter can be applied equally to native-only or to mixed plantings.