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Optional comment: May 2019
This article discusses planting trees, for example in the establishment of a forest garden, or a more traditional type of garden or orchard. Tree planting may also be applicable to planting of a windbreak, and of course reforestation schemes.
The goal is to ensure the survival and health of the young tree. It is important to consider the needs of a new tree (e.g. light, nutrients, water, and protection from strong winds, frosts or animals, pests and diseases). It is desirable to minimize transplantation shock as much as possible. The tree also needs to be helped to outcompete other vegetation until it gets established.
Some state that planting is the most crucial stage of a tree's life. For fruit trees, more die from errors made during planting than from any other cause. If a tree survives sub-optimatal planting, there may continue to be various problems for the rest of the tree's existance.
Once a tree is established, it needs much less attention. For example, trees tend to be relatively drought resistant compared to smaller plant since the roots can reach moisture further down in the soil, and because they create their own shaded microclimate where evaporation by the sun is reduced. Similarly, tree roots are able to access nutrients at deeper soil depths. Also, older trees will be taller than other smaller plants and will dominate in the competition for sunlight.
Prior stages will not be covered here in any detail since they are covered elsewhere. Ideally, the site will have been assessed and a design determined. Depending on local conditions, drainage, water retention features (e.g. swales or hugel beds), soil improvements, etc. may have also been carried out prior to planting.
It is very beneficial if all grass and perennial weeds have been killed or removed as these will compete with establishing saplings and slow their growth. One way of doing this is sheet mulching from the previous autmun. Do not use herbicide chemicals which will kill soil fauna. While that is the preferable situation, in the event that readers have not carried out such preparations or have not need to, it is assumed in the rest of the article that the planting site has grass as groundcover, e.g. garden lawn or pasture field.
The exact position of each tree according to the design is marked by placing stakes in the ground. As a reminder, it is very important that the placement of trees be considered with reference to the mature canopy spread, not planting trees too densely where they will compete with each other for light. In a temperate climate forest garden, planting the tree layer too densely results in a closed canopy with insufficient light penetration to allow lower layers to be productive, and also likely will result in a lot of future pruning or even removal of trees.
Planting a tree is easier if there are at least 2 people.
- Spade and fork: Long-handled digging spade and garden forks require less bending over, and less muscular effort to produce leverage. Modern gardening tools developed from mining tools which were designed to be used kneeling down. Furthermore, people are on average taller than they were 200 years ago.
- Sledge hammer
- Tree tie
- Mycorrhizae fungi
- Watering can or other watering source
- Tree guard or spiral
- Mulch (e.g. chipped bark)
Best time to plant
This depends on what type of trees you are planting.
Between October and April.
Avoid planting when the ground is frozen or after heavy rain when the ground is waterlogged. As a general rule, if the soil is sticking to your boots, digging will damage soil structure. Consider waiting for things to dry out more.
Sometimes it is advised to dig the hole a few days prior to planting. However, this may lead to the surface of soil in the hole becoming hardened.
When a hole is dug, the removed soil is decompacted. Even after firm backfilling, the soil that is backfilled will be relatively looser than the surrounding undisturbed soil, particularly if the backfill is ammended with compost. This means that water will tend to drain through the disturbed soil more readily, and may even pool at the bottom of the original hole (a problem in heavy soils). Waterlogged soil may easily lead to rotting of the roots. The roots of a tree or shrub which encounter the "wall" of undisturbed soil may be deflected and stay within the confines of the original hole. This is not a good situation since anchoring roots need to grow out laterally for some distance in order to support the tree and allow it grow to a mature size without it being top heavy and vulnerable to windthrow (uprooting during storms). Furthermore, if the roots are restricted in a small volume of soil, the tree will become easily stressed as it cannot get enough nutrients or water. This can stunt the growth.
Generally, the hole should be at least twice as big as the root ball of the tree. This gives the roots space to move out of their root ball and not immediately encounter the edge of the original hole. Some advise a hole 2.5 or 3 times as big as the root ball.
A square hole may be better than a round one as the extra space may encourage the roots to grow out laterally from the original hole. When the roots grow and encounter undisturbed soil at the edge of round hole planting, they may be deflected and end up going round in circles. Conversely
This is where the spade is driven in to the sides of the hole, like the spokes of a wheel. This prevents the roots encountering a continuous wall of undisturbed soil when they reach the edge of the original hole.
Consider placing the topsoil and the subsoil in different piles when digging the hole.
Consider putting stones in the bottom of the hole to encourage drainage.
Some advise putting a dead animal in the hole, claiming that the release of nutrients such as calcium as it decomposes will be of great benefit to the establishing tree. Indeed, sometimes trees are used to mark the burial spots for pets or even humans for traditional, religious or otherwise sentimental reasons.
Firstly, the site should ideally not be too exposed to wind, particularly the salty sea breezes of maritime exposure which many trees will struggle with. It may be advantageous to establish a windbreak before planting.
Staking is intended to give the tree support while the roots are becoming established. However some advise against staking completely claiming that the stem, branches and roots will all develop to be stronger without any stake. Generally speaking however if the tree is top heavy or strong winds are a possibility then staking is desirable.
Often the stake is removed after 1 or 2 years as it is no longer needed. However, neglected stakes can cause damage to the tree.
Sometimes stakes are intended to be permanent. For example, fruit trees on dwarfing root stocks may benefit from permanent staking.
Usually stakes are just lengths of wood, square (e.g. 3cm by 3cm / approx. 1 inch by 1 inch) or round in cross section.
Length Shorter stakes may be better than long stakes as it allows the trunk to flex and strengthen in the wind. Shorter stakes encourage strong root growth while longer stakes may result in the tree being reliant on the stake for support. Recommended stake lengths include 0.5m (1'8") above ground level, with the original length being 1-1.25m (3-4').
Trees trained in the form of pyramids or spindlebushes benefit from a permanent long stake.
Vertical stakes can be used. Stakes at 45 degrees are angled away from the root ball and so are ideal for planting pot grown trees.
The stake should be downwind (leeward) relative the to the direction of the prevailing wind. If the stake is placed upwind (windward) then the trunk may be chronically blown against the stake. The constant contact may create a wound which can be a route of entry for disease. For multistemmed trees and shrubs, the stake can be tied to the largest stem.
2 or 3 stakes can be used as an alternative to one very large stake.
Put the stake in the planting hole before putting the tree in the hole. Doing it while the tree is in the hole may damage the roots of the tree. However, many sources advise staking after the tree has been planted.
Hammer the stake into the ground (use a sledge hammer). Needless to say the stake needs to be very strongly set in the ground.
Root ball preparation
The root ball can be thoroughly soaked. Do not do with with a strong jet of water as this will lead to loss of soil and expose the roots unnecessarily. It is better to soak the root ball in a vessel of water, e.g. a bucket.
Loosen the root ball by gently digging fingers into the sides of the root ball and easing roots outwards. Do not snap the roots. This encourages roots to grow into the soil. This is particularly beneficial if the tree is pot bound.
A length of wood can be placed across the hole to easily judge the level of the soil at the planting site relative to the "Nursery line" (the original level of soil in the container).
If the level of the tree is too low, add more topsoil to the mound at the base of the hole. It is too high
If the tree is planted too low in the hole, this can result in a few different problems. Firstly, surface water will tend to drain into the depression. If the soil around the trunk is allowed to be waterlogged, many trees will sustain trunk rot and die. Secondly in the case of grafted trees, if the scion is buried, the grafted part may start to root rather than the rootstock. Any intended influence of the rootstock may be lost (size, hardiness, vigor, disease resitance, yield). For example, what was intended to a dwarfing apple tree might instead start to grow into huge tree.
It is important to backfill the hole with the native soil. If rich compost and fertiliser are used, then the roots will not be encouraged to grow out of the original hole. However, some advise to use a mix of 3 parts soil to one part compost.
Try not to leave any air pockets next to the roots in the backfill. The backfill should be fairly firmly tamped down, which can simply be done with a boot. It is important the stem is held upright by another person while backfilling and firming the soil down the sides of the root ball. The final resting position is as close as possible to vertical. If the tree is planted with the stem at an angle, it will always grow at that position and will be unbalanced.
- The Fruit Tree Handbook. B Pike. Green Books, 2011
- Cite error: Invalid
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- Wilson, M; Royal Horticultural Society (2007). New gardening : how to garden in a changing climate. Mitchell Beazley. ISBN 9781845333058.
- [https://www.rhs.org.uk/advice/how-to-plant-a-tree How to plant a tree (Royal Horticultural society).}
- Seymour, M (2014). The New Self-Sufficient Gardener: The complete illustrated guide to planning, growing, storing and preserving your own garden produce. Dorling Kindersley. ISBN 9781409346784.