The site analysis will have identified the ‘given’ masses (e. g. buildings and existing vegetation masses), as well as open spaces (e. g. paved surfaces, rock outcroppings, open water and zones of low vegetation). The use analysis will have identified currently open areas where vegetation masses are needed for enclosure, screening or spatial formation. It will also suggest the need for open spaces to accommodate specific activities.
From these two sources, a mass/space plan can be developed. The importance of this plan, as the framework within which more detailed design will occur, cannot be overemphasised. Without such an overall structure, the designer can easily be diverted into selecting and placing individual plants and other elements in the landscape, rather than creating a cohesive, flowing design. Ultimately, the masses in the proposed mass/space plan will be translated into forest and shrub groupings, as well as enclosing structural elements (e. g. walls, fences and arbours) on occasion. The spaces will be translated into plant groupings based on naturally evolving old fields and meadows, wetlands and rock outcrops, or, in some situations, into lawns, open-water areas, decked and paved areas.
One of the major challenges in utilising native plant community groupings as design elements is to maintain coherence whilst accommodating the proposed human uses within a site which has many disparate and fragmented elements. Doing a series of quick mass/space diagrams can be of great help in meeting this challenge. Whilst there can be no formula for determining the form of masses and spaces, a useful analogy and inspiration in many situations is the river. The path taken by a meandering river characteristically creates a changing sequence of spaces and views, as well as a sense of mystery, always enticing the observer to see what is around the next bend. Furthermore, as a river carves out its channel, it tends to cut away at the outside of curves, and to deposit sand and/or gravel on the inside of curves. The result of this process is to form a flowing space in the landscape, wider in some places than in others, with an everchanging view as one moves through it. Translated into a designed landscape, the river-like space may be interpreted as a pathway or zone of low-growing or periodically mown vegetation. Adjacent to the ‘river’ may be ‘banks’ of taller vegetation, for example grasses, sedges and wildflowers that grow to a height of two to six feet. This zone may vary in width, becoming broader at the inside of curves in the river-like space it encloses. It may grade into a zone of shrub drifts, which themselves may grade into a forest community, depending on the size of the area.
The width of river-like spaces obviously will vary from site to site, and with the need for enclosure or mass relative to openness or space. In some situations, it may emulate a broad, expansive river; in others, where space is more limited, it may more closely resemble a stream.