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Scotland's Native Trees and Shrubs
Design and build
Most new trunk roads are now constructed in accordance with the Design and Build form of contract. Design and Build is a generic term that refers to various forms of contract where the contractor takes responsibility for the detailed design, construction and maintenance of the works for a defined period within a quality management framework. In this form of contract, no longer is it necessary for the client to detail the landscape planting design in the form of specifications and detailed drawings. Wherever possible, the planting design is expressed in a non-specific way. A specimen design drawing is prepared by the client indicating the absolute commitments made during the planning and consultation stages, scheme-specific landscape design objectives and the minimum standard of planting design that would be acceptable. Absolute commitments could be details of a particular landowner's requirement for a specific form of hedging or tree planting along a boundary. Landscape design objectives could include providing a screen to obscure a view of the road or could indicate an area where a drainage filtration pond is to be designed to include planting that will maximise ecological value.
A new technique of 'rock architecture' is evolving within the Design and Build form of contracts to ensure that rock cuttings look as natural as is practicable. This cutting is only six months old. Carefully designed natural arrangements of native trees and shrubs of local provenance have subsequently been planted to complete the design.
This is a relatively new and developing form of contract for landscape work and not without teething problems. The main issues have been that some landscape designers have succumbed to the temptation to select cheap species and poor quality stock at the behest of their paymasters to reduce the costs of the works.
The quality of landscape planting design of early Design and Build schemes consequently suffered dramatically. The small percentage of evergreen species, native and non-native, that usually cost more than deciduous species, is testimony to this weakness in professional commitment by some landscape designers. The remedy rests with the client. The contract requirements must be as prescriptive as is necessary to deliver the appropriate quality of design required by the client. If the client expressly requires a specific percentage of evergreen species, or indeed any other specific requirements, for example that all birch be cell grown, they must be prescribed fully. Another course of action for the client is, only to approve landscape designers who can be relied upon to uphold the appropriate professional standards of design and not be persuaded, for example, by commercial pressures, to reduce the quality of design or materials.
As a result of these early teething problems there has been a noticeably increased interest by main civil engineering contracts managers in the planting sub-contract. The contract managers are demanding a higher standard of performance from their sub-contractors and adopting 'a do it once and do it right' mentality. The Scottish Executive is responding to this initiative by reviewing the quality of the contract documentation, their administration procedures and working with the landscape industry to develop techniques for improving the transplanting performance of native stock. Design Development Plots are now incorporated into some schemes to try new techniques which provide an opportunity for long-term performance monitoring. Currently discussions are taking place within the tree and shrub nursery industry about growing native species in 'deep-root' containers to simulate natural shoot to root ratio characteristics.
Trials are in place to assess the performance of a new product recently introduced on to the market where native companion species are selected in accordance with a NVC type and grown together as one unit as they occur naturally. The assertion in this case is that such units have an improved transplanting and growth performance together with an enhanced contribution to biodiversity and landscape character.
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