The council will undertake and follow the guiding principles as set out below in the delivery of the Tree Planting Strategy.
Pest and disease resilience
We will:
- keep aware of current threats. We will do this by working with nationwide colleagues and with those from industrial and government bodies
- consider the use of species/varieties with proven disease resistance when addressing specific threats. For example Dutch elm disease
- grow from trees displaying resistance to the threat. For example Chalara ash dieback
- try to plant no more than 10% of the same tree species, no more than 20% from the same genus and no more than 30% from the same family, during our annual planting programme
Over reliance on specific tree groups can reduce biodiversity. It can also leave tree populations vulnerable to severe damage if there are outbreaks of host specific harmful pests and disease.
Appropriate site/tree selection
When choosing trees or sites we will:
- match tree types to site conditions. This helps achieve high rates of strong establishment. It also reduces plant stress/post-establishment maintenance pruning.
- match the final size and spread of the tree to the available space
- consider NHBC (National House Building Council) building near trees. This provides useful information relating to approximate mature height and water demand of commonly found tree types.
- share reporting of significant diseases seen. This provides a history of disease on site or in a wider geographic area.
- consider soil properties such as drainage, pH, soil type and structure
- consider the presence of potential frost hollows. A frost hollow is a low point in the landscape where cold dense air collects overnight and frost is more likely to form.
- look at exposure to prevailing or localised (venturi effect) winds or exposure to salt-laden winds
- look at vulnerability to seasonal waterlogging or drought events
Ensuring high quality procurement
We will:
- source external plant material from certified UK homegrown suppliers. We prefer that these are local but not at the expense of stock quality
- introduce a requirement for ‘plant passports’
- use local provenance wherever available
- consider seed harvest from and the propagation (limited scale) of specimen trees. The existing gene bank will supplement Arboretum trees (historic association, for example cork oak / Quercus suber)
- consider seed collection and propagation/establishment of trees with local provenance, our aim is to use in-house facilities in the future
Planting method – the handling, planting and maintenance of new trees
Timing and quality of planting operations
We will:
- consider that the best tree planting months are December and January. However, planting may take place between mid-November and mid-February. This is subject to weather and ground conditions.
- aim to not plant outside the ‘traditional’ tree planting season as this is undesirable due to physiological stress leading to poor pathogen resistance
- recognise that fluctuations in plant phenological periods may shorten or extend the best planting period
Tree sizes at planting
We will:
- choose trees of a standard size. We prefer that this is 10 to 12cm girth at a 1.0m height. The size may range from a minimum of 8 to 10cm to a maximum of 12 to 14cm. Fully containerised trees ideally should not exceed 45L in pot volume due to manual handling considerations
- only use larger specimens in unusual circumstances. This is because they are likely to require mechanised handling, which we will discuss with the client/contractor on an individual basis.
Pit preparation
We will:
- make our tree pits rectangular in shape. These will have a minimum length and width of 75cm.
- fork over the base of all tree pits to a minimum depth of 15cm below the containerised root system
- perforate the side walls of the containerised root system to encourage developing roots to access the surrounding soil
Installation
We will:
- always cover tree roots to prevent the drying out of roots
- remove any container or wrap directly prior to planting. Then we will cover roots with infill material
- avoid planting when there are cold or drying winds
- place the root collar level with nearby ground levels. We will keep it free from contact with mulch applications and strimmer guards
- wind any irrigation tube (these are a perforated 60mm diameter plastic tube) around tree roots from the base of the pit and to approximately 10cm proud of the surface
- use only quality topsoil or peat-free compost in the tree pit along with original material
- make sure it is progressively ‘firmed in’ to prevent excessive settlement
Tree support
We will:
- make sure that the level of support used is a compromise between the need to protect the tree from mechanical damage and to encourage stem agitation from the prevailing wind. This helps with the development of a strong root system
- install 1 stake as standard and any extra stakes are at the discretion of the supervising officer. Where we install 2 stakes we prefer a crossbar arrangement with a single wrap-around strap and spacer
- position single stakes on the prevailing windward side. To prevent stem chafing we will cut off above the securing tie. We will install these at a minimum depth of 600mm to provide rigid support to the tree for a minimum period of 3 years
- install upright stakes as we prefer this for bare root trees where the rooting pattern allows. We may position these obliquely where necessary to protect containerised stock
Tree protection
We will:
- fit all trees with a short but durable grille strimmer guard, secured with cable ties and into the ground with bio-degradable pegs
- not use spiral tree guards as the majority are not bio-degradable. They are unsightly and add to litter problems. They also tend to cause spindly growth, due to a reduction in space and light and can be hard to remove as the sapling grows
- use wire mesh cages where specified as an added item by the supervising officer, on sites where there is a perceived significant risk of mechanical damage
- apply composted bark/woodchip mulch evenly across surface area of the tree pit between a minimum of 5cm to a maximum of 10cm depth of composted (leaving a minimum 5cm gap all around the stem base)
Tree aftercare
We will:
- prepare a formal and shared record of ‘young tree maintenance.’ We will update this annually to ensure we capture all newly planted trees on a minimum 3-year programme.
- undertake routine tasks in addition to ad-hoc intervention which includes
- weeding
- application of composted bark mulch/ soil dressing
- formative pruning
- adjustment of stakes and ties as needed
- reduction from full to half-stake height as soon as practical. The aim is to have all standard trees free-standing 3 years after planting.
- water the trees at the instruction of the supervising officer
Tree species/cultivar choice
We will:
- decide the right tree types following careful consideration of the site’s unique characteristics and the goals of the planting scheme
- avoid tree types vulnerable to current disease threats
- avoid tree types which are the subject of plant health orders. We will instead consider alternative species which have proven resistance
- aim for a strong theme of uniformity in certain areas. We will do this by using a minimal number of tree types for greater visual impact and the promotion of plant communities
Tree characteristics
We will:
- consider the final size and spread of the trees. Size at maturity must match the available space.
- consider the rooting pattern and vigour
- consider the plant association and any negative or positive influence on nearby tree or shrub cover. This is both on and off-site.
- consider the fruit type and quantity
- not encourage the introduction of heavily fruiting trees such as Malus ‘John Downie’ or any orchard-type varieties grown for their fruit. The exception is if we are looking to deliver orchard areas.
- avoid varieties which show epicormic/basal growth if we do not prune them
- avoid varieties which produce ‘suckers’ growth
- avoid varieties which have poison fruit, seeds, or foliage
- avoid varieties which develop large thorns and sharp growth at low level (for example Gleditisia, Robinia, Kalopanax species)
Whip planting
We find that the planting of whips alongside standard trees brings different benefits.
Whips are:
- young bare-root saplings, usually around a year old. We buy these in bundles or as single plants.
- normally available between November and March and come in three sizes:
- 30-45cm
- 45-60cm
- 60-90cm
The 45-60cm size are the most successful to grow and are most suitable for large-scale planting schemes
- easier to plant than standard trees. This can be a fantastic way to get communities involved. Looking after the trees will be an ongoing project as they need weeding, any vandalism needs noting and tree guards need checking
- versatile. You can use them for hedge planting, creating scrub areas or re-wilding
- featured prominently in our tree planting plan
Hedge planting creates valuable habitats and corridors for wildlife. New hedgerows that link with existing hedgerows or other habitats such as scrub or woodland are valuable for wildlife and biodiversity.
The planting of trees and hedgerows can create a natural barrier to flood waters. They can reduce sediment drawn into watercourses and increase water absorption into the ground. Trees can also capture pollutants contained in run-off such as fertilisers and pesticides.
Rewilding is now a choice for land management as it helps restore ecosystems and supports greater biodiversity. Whip planting is a low-cost method of ecological restoration. Restoring native plants to habitats is vital to preserving biodiversity across the district. By creating a mixture of native plant gardens and rewilding areas across the district each patch becomes part of a collective effort to nurture and sustain the living landscape wildlife.
Climate change
There is uncertainty in the predictions for future seasonal weather patterns. The rate of extreme weather events is becoming more frequent. Current projection is a trend towards hotter, drier summers and warmer, wetter, windier winters. It is therefore wise to consider the use of both native and exotic species. This will build-in longer term resilience and allow us to ‘hedge our bets.’