Tree planting 'how to' guide

Part 3 - Why Plant a Tree

 

The following sections are extracted from the Arboricultural Association publication “An Introductory Guide to Young Tree Establishment” (2022).

 

Why Plant a Tree

 

Planting a tree is one of the best things anyone can ever do. Trees do so much for us, bringing our communities environmental, social and economic benefits and generally helping society. They are multi-functional infrastructure, doing many different things at once. Some of these benefits can be quantified and valued; others are less tangible but no less important. Trees can...

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• Cool our urban areas

• Reduce flooding

• Improve air quality

• Slow traffic speed

• Reduce certain types of crime

• Improve physical health and mental wellbeing for people

• Provide habitat for a wide range of insects, birds, mammals and fungi

• Sequester carbon

• Look beautiful

• Screen views of undesirable buildings or infrastructure

• Add cultural and heritage value to an area

• Provide a sense of place

• Help community cohesion and local pride

• Boost commercial activity

• Create employment and career opportunities​

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Many of the benefits associated with trees increase as the tree grows, and it is often the case that the larger the canopy, the greater the benefit. One common metric by which to measure the success of our urban forests is canopy cover – assessing how much of a given area is taken up by tree canopy when looking down from above. However, these canopy cover targets will never be achieved through tree planting alone – we must retain and protect existing trees wherever possible and take appropriate steps to care for those that we do plant. There are many reasons to plant a tree, and just as many reasons to make sure it is properly looked after.

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Where to Plant a Tree

 

Planting a tree is a long-term investment, and it is unlikely that the person who is doing the planting will ever see the full benefit of their efforts. Tree planting is a gift for future, as well as current, generations, and we must consider the medium- and long-term implications of what we are doing. This is particularly true when selecting a location for a new tree. The question of where to plant a tree often goes hand in hand with the question of what tree to plant – a particular location might need to be found for a given species, or it might be necessary to select a species for a particular site.

 

This introductory guide is likely to be most relevant to people planting trees in soft landscapes (grass areas, gardens and parks) rather than hard landscapes (such as streets or plazas), but the considerations are equally relevant regardless of where the tree is being planted. When looking at a potential site it is important to consider the tree not as it is on the day of planting, but in the context of its likely final dimensions – as it should be in 10, 50 or 100 hundred years. Remember to always make sure you have the permission of the landowner before planting a tree.

 

Think about how close the tree will be planted to buildings, infrastructure or existing vegetation. A tree planted immediately adjacent to a building will grow outwards, seeking the light. A tree planted beneath the canopy of an existing tree is likely to struggle. Planting a tree too close to a lamp column or overhead utilities will mean that regular pruning is required in the future. The same goes for planting trees which will ultimately obscure sightlines – of views or buildings, but even more importantly of traffic lights, signs and visibility for safety reasons. It is also worth considering how easy it will be to reach the tree in later years for watering and maintenance.

 

What is below the ground is just as important as what is above it. When matching a tree species with a location, consider the soil type. Is it sandy, loamy or clay? Is it free draining, or prone to waterlogging? Is there any risk that it might be contaminated? Soil can be tested to find out more about its composition and condition. Underground utilities such as gas, electricity or water often mean that a site which looks suitable for planting proves unsuitable. Hand-dug trial holes may be required before the final pit is excavated – consider having the site scanned for underground utilities before starting. Underground utilities can kill, so if you are in any doubt, always consult an appropriate professional. Utility companies will provide, on request, mapping with the location of their services infrastructure.

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What Tree to Plant

 

Trees are multi-functional infrastructure – they do lots of things at once, to different extents – and some species will be better or worse at certain things than others. When selecting a tree species for planting, it is therefore important to consider what the ultimate aims of the planting are. Once you know what you want to achieve through the planting, it becomes much easier to determine which species is most appropriate. In addition, the decision about what to plant will also be influenced by the location of the planting, particularly with regard to how much space is available. Please remember when selecting a tree species that in order to mitigate the risks of climate change and tree pests and diseases, and to maximise the environmental, social and economic benefits our urban forests bring, diversity in tree species is critical. When considering amenity trees, ‘non native’ species are just as important as ‘native’ species. Tree species selection is a complex process. There are many factors to consider, and there is not enough space in this short guide to fully explore them all. There are some key questions to think about which, when combined with additional research and input from a professional arboriculturist where required, can help inform the decision making process. These questions include:

 

• How much space is available for the tree to grow to its final dimensions?

• What are the main characteristics you are looking for?

• These might include fruit, autumn colour, interesting leaves or bark, and many more. 

• What are the soil conditions of the proposed location? Acidic or alkaline, free-draining or prone to waterlogging?

• How much maintenance does the species you are considering require?

• Are there any particular pests and disease of concern locally, either present now or likely to arrive in the future?

• What are the preferences and social values of the local community?

• What trees are currently in and around the site, and would you prefer to complement or contrast with them?

 

In addition to the species, you must also consider other factors, such as size and root stock. Trees are supplied in a variety of different sizes at the time of planting, from whips Many trees planted for amenity purposes have a girth size of between 10cm and 18cm. Large trees are often preferred because they create instant impact and are better able to withstand vandalism. a very young tree, perhaps not more than 1m tall and with no side branches) up to semi-mature specimens.

 

However, they are also more expensive and can be more difficult to handle, plant and establish. Small trees are easy to handle and plant, can establish quickly and are often cheap However, they may require substantial protection for the first few years after planting. The main types of root stock available are bare root, rootballed and container grown. As with selecting a size, the advantages and disadvantages of each root stock type should be considered. Bare-root trees tend to be cheaper and easy to handle and plant, but the range of species available is often relatively limited and they must be planted within the standard October to March planting season. They will also have lost much of their fibrous root system in production. Rootballed trees come with their fibrous root system and more species are available, but they can require more specialist handling and planting. Containerised trees can be much easier to transport and plant, offer considerable species choice, preserve the fibrous root system and if necessary, can be planted outside the standard planting season (with appropriate aftercare). However, they are considerably more expensive than bare-root trees.

 

One of the most important considerations when sourcing a tree is biosecurity – preventing the spread of tree pests and diseases. Oak processionary moth and ash dieback (to name just two) were both imported to the UK on trees sourced without proper biosecurity practices. You should only ever purchase a tree from a reputable nursery with strong biosecurity practices. Trees should be UK-grown or, if imported, should have been subjected to an appropriate quarantine period before planting out.

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How to Plant a Tree

 

In order to ensure that your tree has the best possible chance of reaching maturity, it is important to plant it properly. Always undertake work of this nature safely and responsibly, including taking all steps to ensure that you have permission from the landowner and are certain that no underground utilities are present. Some of the specifics around planting may vary with different tree sizes, but this guidance focuses on trees with a stem girth of around 10cm+, up to the sort of size which can be safely handled by one or two people. It also focuses on planting in soft landscapes. In addition, this guide does not cover additional infrastructure which might be used, such as underground guying (a support mechanism), root cells, tree guards, tree grilles, root barriers or watering pipes. If you are using any of these systems, please follow the manufacturer’s guidance.

 

The hole for a new tree should be no deeper than the root ball/container, but approximately twice as wide. Holes can be circular or square, and different experts have different ideas about which shape is best. In soft landscapes, the soil closest to the surface might be better quality than the material found further down, so consider putting some to one side in order to backfill around the roots once the tree is in place. Measure the depth of the hole against the depth of the root ball before removing any container or hessian. It is very important to ensure that the final ground level around the stem matches the nursery line on the tree, which is the soil mark where the above-ground and below-ground bark meets.

 

Before setting the tree in place, consider if any formative pruning is required to remove damaged, broken or rubbing branches. It is much easier to do this before planting rather than after. If the tree has a co-dominant stem – i.e. more than one clear central leader – consider pruning back the ones which are not wanted with clean, sharp, disinfected secateurs. However, do not prune the main leader as this will disrupt the tree’s hormonal growth pattern. Once the tree is in place and the packaging removed, backfill the hole with some of the material you previously excavated and compact with a boot or the end of a wooden support stake. Keep checking that the tree is straight during this process.

 

There are many different methods and styles of securing a tree in place after planting, and this choice will be influenced by a range of factors – including the size of the tree. A tree will respond to wind forces by adding new growth to its stem, and it is therefore important that it has room to move in the wind whilst being adequately supported. Crossbeams and diagonal staking are not recommended because they prevent the tree from moving in this way, which can create a weakness. This guidance recommends planting more substantial trees (with a stem girth of 10cm+) with two timber stakes and rubber ties. The orientation of the stakes may be influenced by aesthetics and the prevailing wind direction. Take care when driving the stakes into the ground: consider both underground utilities and operator safety when using a stake driver and be careful not to damage the tree. Sometimes it is easier to install the stakes before the tree is placed into the hole. Always ensure that the stakes are driven through the ground and not the root ball or container of the tree. Ties should be attached at approximately 1/3rd of the total height of the tree. Stakes and ties should always be removed when no longer required. For smaller trees, such as whips, a bamboo cane and suitable tree guard should provide adequate support.

 

The recommended surface material to use around newly planted trees is bark mulch. This suppresses competing vegetation, helps retain moisture, breaks down over time to enrich the soil and ensures that grass-cutting equipment is kept at a safe distance from the base of the stem. A depth of 5–10cm of mulch should be applied after planting, ideally covering a circle around the tree of a minimum 1m diameter. Make sure you do not pile mulch directly up against the stem.

 

As a general rule, the tree planting season in the UK extends from October to March. Deciduous trees should ideally not be planted when they are in leaf. Consider engaging the local community in your tree planting, and if possible, it can be beneficial to leave the nursery identification tag in place so that people are able to identify the tree afterwards. Always water your new tree after planting.

 

Establishment - Young Tree Aftercare

 

The years immediately after a tree has been planted are in some ways the most important in its life. This is the time when the young tree is most vulnerable – old enough to be planted out into the landscape, but young enough to still require plenty of care and attention. One of the most important tasks for the first years after planting is watering, which is dealt with in a separate section of this guide. However, there are also plenty of other considerations.

 

In a soft landscape situation (and in some hard landscapes) the area immediately around the tree will have been covered with organic bark mulch. This helps protect the tree from strimmer damage, removes competition from weeds and grass and is hugely beneficial to the tree overall. However, this mulch will break down sooner than you think and it is important to keep it topped up regularly. More information about mulch can be found elsewhere in this guide (see ‘How to plant a tree’).

 

If the tree has been supported with above-ground stakes and ties then these will need to be checked every year after planting. Adjust the stakes and ties as necessary, paying particular attention to ensuring that they are still doing the job they were intended to do. Painting the top of each stake with a different colour depending on the year in which the tree was planted can assist with identification and management. Tree support systems should be removed when they are no longer needed; leaving support systems in place for too long can cause damage to the tree.

 

Much of the pruning work undertaken with chainsaws many years after planting can be avoided if a tree is maintained in its first few years using hand tools to create smaller wounds from which the tree can recover more easily. Consider removing damaged, dead, broken or crossing branches, paying careful consideration to the future structure of the canopy. Always adopt good biosecurity practices to reduce the risk of spreading disease.

 

Visiting young trees in the years after they have been planted also provides an opportunity to check their overall health. Whilst detailed diagnosis of a condition will require professional arboricultural input, there are certain problems which should be easy to identify. These might include a failure of the tree to come into leaf in the spring; wilting, yellowing or die back of leaves and shoots; or exudations from the stem.

 

Around three years after planting the tree should be inspected with a view to deciding whether or not it is ready to be removed from the young tree maintenance programme. If it looks like the tree could do with some more establishment time then simply return the following year until you are satisfied. Once the tree seems secure and established it is time to take away the stake and ties and remove the tree from the young tree maintenance programme. It will now require inspection (and any associated maintenance work) as part of the wider tree stock.

 

Tree Watering

 

One of the main causes of death in newly-planted trees is a lack of water. In simple terms, water is drawn up by the tree via the roots, through the stem and branches and then exits the tree via the leaves in a process called evapotranspiration. A newly-planted tree will not have an established or extensive root system, meaning that in the summer months when Please visit: www.treecare.org.uk/watering the canopy is in full leaf it will struggle to bring in enough water from the ground to balance what is being lost through the leaves. For the first few years after planting, trees need our help in order to find that water.

 

Tree watering is an inexact science and there are many variables involved. These include tree species, size, condition, root stock, soil type, location, weather and climatic conditions. It is not realistically possible to take all of these variables into account in a meaningful way and most recommendations will, therefore, necessarily be oversimplified. The advice provided here is based on a collaboration between the Arboricultural Association, the Association of Tree Officers, the London Tree Officers Association and the Municipal Association of Tree Officers. This group of organisations has also produced the tree watering tags referenced within this guide and available online, which can be affixed to newly planted trees to encourage passers-by to water them.

 

We recommend that for the first three years after planting, a newly-planted tree should receive approximately 50 litres of water each week throughout May, June, July and August (in the UK). Depending on seasonal variations it may be necessary to start watering trees as early as April and continue as late as September. These 50 litres can be added to the tree in one visit, or spread over multiple visits. Watering will ideally be carried out in the early morning or in the evening, when temperatures are lower than during the day.

 

Wherever possible, water used for irrigating trees should be sustainably sourced. Harvested rainwater is ideal, and should be used in preference to potable (drinking quality) water. Recycling grey water, such as from baths or washing-up bowls, is also an option to irrigate trees but the impact of soap and detergent on soil structure is not fully understood. However, in times of drought when using potable water is expressly banned, the benefits of grey water likely outweigh the potential risks. In general terms it is of great importance that we seek to move away from using potable water in tree care wherever we can.

 

A watering pipe is sometimes installed alongside a tree. If a watering pipe is present then approximately half of the water should be poured down the pipe and half added to the ground surface around the tree. Some trees are planted with watering bags; if your newly-planted tree has a watering bag then fill it in accordance with the manufacturer’s specification. Try to ensure that the water is actually penetrating the ground and is not simply being intercepted by the layer of mulch on the surface.

 

Under some circumstances it is possible to overwater a tree, which can in itself lead to health problems. However, in general terms it can be said that the risk of a lack of water is greater than the risk of an excess of water. When planting in clay soils it may be advisable to cut a drainage channel, extending away from the base of the pit and filled with gravel, to prevent waterlogging. If you are in any doubt then please speak to an arboricultural professional. Note also that trees in full leaf can still require watering even when it has recently rained, and that a light shower is not going to be sufficient to deliver the required level of water to the roots of the tree.

 

Bibliography

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Arboricultural Association

British Standards

National Plant Specification

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If you'd like advice about your tree planting plans or have questions, please feel free to reach out to GGCN members at ggcommunitynetwork@gmail.com. Happy planting! ​

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