Appendix G: Landscaping on new developments and in highway-improvement schemes

1.1 Well-designed landscaping can have a very positive influence on the final appearance and attraction of a new development. Including planting and areas of open space in the development layout can significantly improve the environment for new residents, softening the appearance of new buildings and giving the development an established appearance.

1.2 Carefully-designed tree planting, in particular, has a significant effect, providing areas of shade and screening at a number of levels. If we are to adopt areas of landscaping, it is essential that you follow high standards of practice so that landscaping becomes well established. The design of any landscaping should ensure that long-term maintenance requirements are kept to a minimum. You can achieve this by providing enough space for new planting to develop to maturity. Providing space between a landscape feature and a new building is also important to ensure that both can exist together.

1.3 It is essential that you ask a chartered landscape architect for professional advice on all landscaping matters relating to new development.

1.4 When you have finalised the overall layout of the development and have established the areas for soft landscape works, you can decide on the planting proposals.

1.5 All planting needs to be carefully selected taking into consideration the size it will grow to. This applies particularly to trees and includes both the canopy spread of the tree and the root system. As well as providing adequate space for trees to grow, you need to consider the effect trees will have on the existing surroundings such as nearby buildings or walls. A tree’s demand for water can have a direct impact on the existing soil conditions. You should not underestimate the effects of soil heave and shrinking - there are guidelines on tree planting in relation to buildings and foundation design in the NHBC Standards 4.2 Building near trees.

1.6 You should also avoid planting shallow-rooting trees close to footways, as there is likely to be a future problem with the roots disturbing tarmac and other hard surfaces.

1.7 With careful planning, you can easily include effective landscaping in the layout of a new development without significantly affecting the space available and the potential for developing the site. Areas of open space, grass verges, islands and gardens are all potential sites for appropriate planting. However, you should consider the following when planning suitable landscaping.

1.8 The type of planting you can use in landscape schemes will depend on the available space. Traffic islands and open spaces at the centre of a development are ideal locations for individual trees where the tree becomes a focal point (for example, village greens).

1.9 Large open spaces are ideal for planting groups of trees (either single species or mixed), whereas wide verges on either side of a road provide an opportunity for planting an avenue of trees. Shrub planting can provide low-level screening and you can incorporate this into highway-improvement schemes, particularly where you need to restrict visibility (for example, for traffic calming). If you are planting trees and shrubs in a new development, you should include design features which will allow for their establishment and potential growth.

1.10 Less formal areas of open space such as screening bunds provide an opportunity to establish closely-spaced plantations which can develop into effective screens and, eventually, mature woodland. In more restricted spaces, you can consider planting small ornamental trees or shrubs. The design of this type of planting should ensure that long-term maintenance costs are kept to a minimum. As an alternative to mown grassland, you can use shrub beds containing species which provide dense ground cover, but their maintenance costs are usually high and this type of planting often acts as a litter trap.

1.11 We will normally adopt well-designed and planted landscaping on verges and other highway-related land providing that you pay a commuted sum to cover its long-term maintenance. Please see Part 4, Section MC18 for further details on commuted sums.

1.12 We will not adopt new planting within a development if plants are either dead, stressed or failing to establish due to poor design and planting practices.

1.13 As well as considering the amount of space available for new planting above the ground, it is equally important to assess the condition and extent of the soil below ground. During construction activities, surrounding soils can become damaged by compaction and contamination. It is essential that you treat them so that they can support new planting and sustain normal plant development. Compacted soil becomes starved of oxygen, which is essential to the survival of plant roots. Compaction can be improved by deep ripping or cultivation (or both), which allows oxygen to penetrate the soil and improves drainage. You should remove soil that is badly contaminated from the site and replace it with fresh top soil. It is also beneficial to apply an organic surface mulch such as pulverised bark to a planting area. This will help retain soil moisture, suppress weed growth and encourage the colonisation of soil organisms (mycorrhizae) which are beneficial to plant roots.

1.14 You should carry out a soil survey before planning or designing any new landscaping and remedial works to identify and treat poor ground conditions. It is a waste of time and money to plant trees and shrubs into damaged and poorly-prepared soils.

1.15 You should design any hard surfaces close to the planting site to withstand plant roots developing and expanding. You can do this by using a sub-base which, although load bearing, contains a proportion of soil and air space. You can also use root deflectors in the planting site to minimise the risk of damage to hard surfaces. These consist of an artificial barrier placed round the tree, which then deflects root development downwards and away from vulnerable surfaces. Hard surfaces should be permeable to allow drainage and oxygen penetration to the soil below.

1.16 Tree grills are often fitted around the base of trees particularly when they are planted in paved areas. Although these provide a neat appearance to the tree station and prevent compaction to the surrounding soil, they are expensive and can severely obstruct the development of the tree if not regularly checked and eventually removed.

1.17 This is a complicated process with many aspects to consider. To ensure that new landscaping improves and co-exists with a new development through its normal life span, it is essential that you select the correct species for each site. It is important that you know the potential mature size of any planting to ensure there is enough space and the planting is not likely to spread onto other development features (for example, roads, accesses, houses and so on)

1.18 With tree planting, in particular, you must know the potential size, shape, growth habit and ornamental qualities of a tree species so you can select the most appropriate tree for a site.

1.19 In rural areas, you should use native plant species to help blend the new development into the surrounding landscape and reflect the local character of the area.

1.20 You can find a list of some tree and shrub species in Table L1. This indicates the space required for each species and suggests a range of appropriate uses. Table L2 lists tree species you should avoid.

1.21 You should ask a professional landscape architect for advice when you are selecting species. This will make sure that new planting is suitable for the existing site and soil conditions and is appropriate to the particular location.

1.22 To make sure plants are properly established, the planting site should be suitable and well prepared, and the plants should be carefully handled so they arrive at the site in prime condition. It is also important that plants are well planted and all roots are covered with friable (crumbly) soil which should be firmed so the plants stand upright. Although all roots should be covered, it is equally important that plants are not planted too deeply. The plants should be planted at the same level on the stem as they were when they were in the nursery. Large stock, such as standard trees, should initially be supported with stakes and ties and you should protect all plants against browsing animals such as rabbits.

1.23 Soft landscape works must be effectively established before they are adopted by the local authority and you should design schemes that keep long-term maintenance to a minimum. Where appropriate, you may have to pay a commuted sum as a contribution towards the future maintenance costs. Please see Part 4, Section MC18 for further details on commuted sums.

1.24 In the years after planting, you should remove weeds, adjust ties and guards, prune and, when necessary, water the plants to help them get established. You should do this for at least four years until the plant stands independently, is dominating surrounding vegetation and producing reasonable growth every year. The cost of maintenance operations compared to that of the initial planting is minimal. So it is worth investing in a thorough maintenance programme to ensure that new landscaping reaches its potential and fully complements the new development.

1.25 Maintenance works should meet the relevant British Standards and should always relate to a specific scheme. For example, establishing an avenue of heavy standard trees planted in a grass verge is very different to establishing a forestry plantation.

1.26 All nursery stock used in the landscaping of new developments should be supplied from appropriate suppliers and should meet the requirements of the National Plant Specification and the following British Standard (BS) specifications.

1.27 All stock should be suitably protected when being handled at the supplying nursery, during transport and while being stored on the site. As well as protecting the stock against any physical damage while being handled, it is essential that the roots of all bare-rooted stock are covered, kept moist and not allowed to dry out. If roots desiccate (dry out), fine root hairs, which absorb moisture from the soil, are destroyed and this can quickly lead to the decline and death of the plant.

1.28 All materials used in landscaping new developments and all associated practices and workmanship should meet with the appropriate BS specification or Code of Practice issued by the British Standards Institution.

1.29 Other British Standards relevant to landscaping works include: