Technical Planting Guidance:

Soil

Quarrying and cement manufacture in the Ebbsfleet Garden City site has resulted in large areas of made ground, areas where all topsoil has been removed, quarry overburden e.g. Thanet Sand, or areas with unusually high alkalinity (parts of Swanscombe Peninsula).

To support planting, topsoil may often need to be imported, or manufactured on site using site-won materials or imported quarry waste and green compost. All topsoil will need to be tested to ensure suitability for the proposed planting, at a minimum to BS3882, and ameliorated as necessary to reach that standard. Subsoil likewise to BS8601.

Typical soil depths required:

Soil Permeability

Appropriate drainage is required for all planting typologies. Permeability/percolation tests need to be carried out to guide species selection and remediation measures. These measures include ripping subsoils, avoiding compaction, avoiding handling plastic soils when wet. Where permeability is low, land drainage may be required for areas of amenity grass, and positive drainage will be required in tree pits, to avoid muddy wet areas of lawn, or trees failing to establish due to anaerobic conditions in tree pits.

Right plant, Right place

Appropriate plant species should be selected to suit the particular environment of each site, including drainage, aspect and soil. Species should be specified to suit site conditions, to avoid undue stress that can lead to longer term management issues caused by ill-health, pests and diseases.

Plant Provenance

UK grown plant stock should be specified to minimise environmental impacts. These impacts include reducing transportation distances and the potential spread of plant pests and diseases. Using plants grown in similar conditions to the project site, particularly with a similar climate, and ideally with similar soil types, should increase establishment rates. All these benefits can be further increased by specifying locally grown stock, so where practical, locally grown stock should be specified.

Use of Water

The majority of planting should be specified to suit site conditions, to minimise the need for irrigation to the establishment period, or exceptionally dry hot periods. Watering pipes should be included in tree pits for this purpose.

Exceptions to this are planting on decks, e.g. above car parking, or in high profile areas of courtyards. Automatic irrigation systems may be considered using drip systems, ideally using recycled grey water or rainwater.

Productive food growing will need irrigation, and water taps should be provided for this purpose in local parks or allotment areas.

Biodiversity

Planting a wide palette of plants will enhance site biodiversity, and provide habitat for a wider variety of wildlife. This also creates a more robust public realm, as it provides resilience to the increasing globalisation of plant pests and diseases.

Planting for Pollinators

The use of plants from the Royal Horticultural Society “perfect for pollinators list” will provide pollen and nectar for bees. Select plants with simple flower petal arrangements that bees find easy to navigate.

Globalisation of plant pests and diseases

Trees in particular are subject to an increasing number of pests and diseases. Avoiding over reliance on a narrow range of all types of plants will limit the impact of these.

Check Forestry Commission for specific restrictions on plant pest and diseases at the following website:

https://www.forestry.gov.UK/pestsanddiseases

Check for any current or likely plant movement restrictions:

https://www.gov.UK/guidance/importing-trees-andplants- to-england-and-wales-from-the-eu

Micro-climate

Ebbsfleet Garden City is located within two landscape character areas as shown on the diagram below.

The landscape character of these areas have been shaped by many factors, a key one of which is the micro-climate.

• The “Greater Thames Estuary” area is generally low lying, flat and open, on the banks of the tidal River Thames, so it is exposed to salt-laden winds from the North Sea. - By comparison, the “North Kent Plains” area is inland from the Thames, sheltered behind a chalk spine. Quarrying has lowered land levels, creating relatively enclosed and sheltered conditions.

The landscape character reflects these climate differences. The Swanscombe Peninsula has few trees, and these are often wind pruned. Field boundaries are typically formed by drainage ditches, rather than hedges. Northfleet Embankment has some sheltered areas adjacent to chalk cliffs, including the site of the former Rosherville Italian Garden, but is more exposed on the cleared terraces areas along the Embankment.

Many site have little or no existing vegetation, except around the edges, so new planting will be exposed to wind. Kent generally has a low annual rainfall.

Micro-climate will be a key factor in plant selection, and plants need to be selected to address the site conditions. The diagram on the right gives an indication of where these two main micro-climate zones are, but these should be checked on site.

Plants should be specified which will establish in these challenging conditions, or measures introduced to provide either temporary shelter whilst plants establish, or long term protection.

Tree Planting

The preferred approach is to plant trees in soft landscape, rather than hard paved areas, wherever practical. Soft landscape areas can provide trees with the conditions they require for establishment and growth in the long term.

The tree planting details on the following pages illustrate best practice for planting semi-mature trees in either soft or hard landscape.

Where planting in hard surfaces is unavoidable, suspended pavement systems must be incorporated to provide both support to paving around the tree pit, and sufficient rootable soil volume for the proposed trees.

There are a range of approaches to this, including:

• Deeproot ‘Silva Cells’

• GreenBlue Urban ‘Strata Cells’

• Heicon ‘Amsterdam Tree Sand’

Research has identified that the Cell systems are more effective in supporting tree growth.

Rootable soil volume

Trees require a minimum volume of soil that their roots can grow into, to support their growth after the establishment period, and sustainability over their potentially long lives. The table below shows the volume required. The rootable volume includes topsoil and any layers of washed sand or subsoil that the tree roots can access, up to a combined depth of 1m in soft verges.

Tree pit drainage

Positive drainage from tree pits will be required if ground conditions have low permeability. This is key to tree establishment, and will need to be established by percolation testing at each site. The drainage will only be required during the establishment period.

Tree support

Underground guying should be used for trees in streets and where people need to pass close by them, to avoid creating trip hazards. This method is suitable for trees planted at 20cms girth and above.

Root barriers

Where root barriers are required, these should be positioned as close to the services as possible, and as far away from the tree pits, to enable tree roots to gain access to soil for oxygen, nutrients, water and anchorage. Avoid root barriers on more than one side of trees.

Street tree planting

Planting location and conditions are critical in tree selection. In streets, space can be restricted above and below ground and trees with an appropriate rooting structure and low to medium water demand should be selected. Species for these locations will also have a narrow crown, with modest leaf and branch drop. Where space is less restricted species with wider crowns can be used. The example street tree species in this guide have been drawn from plants that have either been hybridized or have an intrinsic characteristic that makes them suitable for the location. Street trees in general must have a narrow, fastigiate or columnar form which is maintained through its mature life. Individual selection of the trees for the streets will be required to suit each location.

To avoid conflicts with roots, branches, leaves and shading, the location of trees at detailed design stage must be undertaken with careful consideration of the requirements of service runs, of highway standards, of public safety, lighting standards, owner liability, species type and useful life expectancy, and adoption and whole life costs.

A coordinated approach needs to be undertaken that engages: service providers, adopting organisations, and the detail design team.

Service zones need to be clearly established in the public domain, but these must be controlled and regulated with discipline throughout the entire delivery process. The intention is to define the importance of the tree pit zones, ensure that any conflicts are avoided or mitigated thereby avoiding a situation where tree planting design objectives cannot be achieved.

Technical Planting Guidance : Tree planting - soft detail

Technical planting guidance: tree planting - Hard detail

Soft landscape - specification, management & maintenance

Specification

A full and detailed specification for all planting will be required at the detail design stage that is appropriately drafted with references to the relevant British Standards and the National Building Specification (NBS). This specification will cover all aspects of the quality of the planting stock, handling, planting and establishment.

Landscape Management

Landscape Management Plans should be produced for each of the development areas setting out the long term objectives for the public realm, identified by typology and location. Plans should include details of the body that will be responsible for long term management of the public realm assets, and will provide guidance for that body to provide continuity in management to deliver the Ebbsfleet Garden City vision. This is particularly key for planting which grows and develops over time, and the management plan should address this dynamic.

Landscape Management

Plans should be produced for each of the development areas setting out the long term objectives for the public realm, identified by typology and location. Plans should include details of the body that will be responsible for long term management of the public realm assets, and will provide guidance for that body to provide continuity in management to deliver the Ebbsfleet Garden City vision. This is particularly key for planting which grows and develops over time, and the management plan should address this dynamic.

Landscape Maintenance

An appropriate soft landscape maintenance regime is required to ensure that the public realm meets the high standards required for Ebbsfleet Garden City. Sustainable soft landscape maintenance should be considered at an early stage in developing the public realm design and coordinate with the hard landscape maintenance recommendations outlined in Chapter 5. Details of soft landscape maintenance should be set out for each public realm typology and location, including schedules of operations and programme. Guidelines for the soft landscape maintenance of Streets Levels 1-4, Parks and Squares are provided in the following pages.

Soft landscape maintenance guidelines