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Planting trees

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Optional comment: May 2019

This article discusses planting trees and shrubs. Tree planting is a vital skill in areas such as forest gardening, orchard management, windbreaks, reforestation schemes, etc.

Aim[edit]

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). The tree also needs to be helped to outcompete other vegetation until it gets established. It is desirable to minimize transplantation shock as much as possible. This is a disruption in growth caused by a sudden change of environment. Trees grown in nurseries may have been closely planted in sheltered location, perhaps even under cover. At the destination site however, the tree may be exposed to stronger winds, harsh sun or hard frosts.[1]

Some state that planting is the most crucial stage of a tree's life.[2] Good attention to detail before and during planting may pay back greatly for decades into the future.[3] Conversely, if a tree survives sub-optimal planting, there may continue to be various problems for decades or even the rest of the tree's existance.[2][3] For fruit trees, more die from errors made during planting than from any other cause.[2]

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[edit]

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.[4] While planting trees into bare earth is the preferable situation, in the event that readers have not carried out such preparations or have no 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. In this case, remove any weeds that are not grass, and make sure the grass is relatively short before planting.

The exact position of each tree according to the design is marked on the ground by placing stakes, stones, canes or spray paint. 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.

Once the design is finalized, the site prepared and marked out, the final thing to do is aquire suitable plants. Again, this is covered in more detail elsewhere. Aim to transport them carefully and minimize the time between aquiring planting stock and getting them in the ground. To summarize, trees & shrubs are typically available in 3 forms. Part of the reason that tree planting advice is so variable is that for each of these types of stock planting technique might be slightly different, which shall be discussed where relevant in this article.

Container or pot grown

These are more commonly found in garden centres because they can be sold all year round.[2] While they are in pots they are generally easy to move, store and care for.[3] The growing medium is usually a sterile potting soil. They are tempting to customers shopping in the growing season as they can see leaves or maybe even fruit on the plant. When selecting such trees it is best to choose ones which are still dormant (but not dead), i.e. before buds have burst. A tree which has a lot of foliage is no longer dormant and will be far more prone to dying after being planted. A big disadvantage of pot grown plants is that you cannot directly insepct the roots. Pot grown trees are prone to soil exhaustion and becoming pot bound.[2] This is where the roots encounter the edge of the pot and start to grow around in a circular pattern. The roots are also usually growing out of the drainage holes in the base of the pot. Remove the pot before buying to check if it is pot bound if possible.[2]

Bare root

Root balled (Balled and burlapped)

Tools[edit]

Planting a tree is easier if there are at least 2 people.

  • Tree(s) to be planted
  • 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.[5]
  • Stakes
  • Sledge hammer
  • Tree tie
  • Bonemeal
  • Mycorrhizae fungi
  • Bucket
  • Watering can or other watering source
  • Tree guard or spiral
  • Mulch (e.g. chipped bark)

Timing[edit]

This depends on what type of trees you are planting. Generally trees are planted while they are dormant.

Between October and April.[6] Mid November to late March,[7]

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.[2]

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.[8]

Techniques[edit]

Pit planting

This is the most thorough and most common way of planting. This technique is described in the rest of the article. It ensures good contact between roots and soil.

Slit planting

A quick method, which is easier than pit planting, particularly in stony soil. Drive the spade fully into the ground, deep enough for the tree roots, and then lever it forwards to open a slit. Keep the spade in position to hold the slit open, then place the tree. Remove spade and restore soil around the tree.[7]

T notch planting

Another quick method, suitable for areas susceptible to drought but not for clay soils. Drive the spade fully into the ground. Make another cut with the spade, perpendicular to the first to make a T shape. Re-enter the first cut and lever it up, which parts open the other cut. Place the tree carefully between teh parted turf, ensuring roots are all within the hole. Remove the spade and firm down soil around the tree.[7]

Hole[edit]

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.

Remove turf

Turf (sod) is removed with a spade or a mattock. It is also usually broken up into smaller chunks.

Size

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.

Shape

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.[5] 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

Loosen surrounding soil

Loosen the soil at sides of the hole. This can be done with a fork. Alternatively, use a spade and drive it into 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.

Depth

Technique

Consider placing the topsoil and the subsoil in different piles when digging the hole.[8]

Consider putting stones in the bottom of the hole to encourage drainage.[8]

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.[8] Indeed, sometimes trees are planted to mark the burial spots for pets or even humans for traditional, religious or otherwise sentimental reasons.

Some advise putting the turf that was initially removed back at the base of the hole to provide nutrients.[7]

Staking[edit]

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.[2]

Usually stakes are just lengths of wood, square (e.g. 3cm by 3cm / approx. 1 inch by 1 inch)[2] 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.[5] Shorter stakes encourage strong root growth while longer stakes may result in the tree being reliant on the stake for support.[2] Recommended stake lengths include 0.5m (1'8") above ground level,[2] with the original length being 1-1.25m (3-4').[2]

Trees trained in the form of pyramids or spindlebushes benefit from a permanent long stake.[2]

Angle

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.

Position

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.[2] For multistemmed trees and shrubs, the stake can be tied to the largest stem.

Number

2 or 3 stakes can be used as an alternative to one very large stake.

Technique

Some advise to put the stake in the planting hole before putting the tree in the hole. Others advise staking with the tree standing in the hole but before backfilling,[8] and others still say that staking is best done completely after the tree has been planted.[7]

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[edit]

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,[6] which is left for at least 2 hours.

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.

Some advise root pruning to stimulate the growth of new fibrous roots and to remove any damaged roots.[8]

Tree placement[edit]

With the tree ready and the hole ready, the tree can be positioned in the hole.

Some advise first placing some manure at the bottom of the hole, and covering that with a small mound of topsoil.[8] The tree is then placed in the hole with the roots gently spread out over the mound.[8] The roots are arranged so that they lie in the position they naturally want to be in,[8] try not to bend the roots out of position.

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 collar (the mark on the stem where it originally started to grow above ground) or "Nursery line" (the original level of soil in the container). For grafted fruit trees, aim to have the union between scion and rootstock at about 15cm (6") above ground level.[8] In very dry climates, it may be better to plant the tree 15cm / 6" deeper.

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 dig the hole deeper.

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.

If the tree is planted too high, the roots may get exposed and die.[7]

Backfilling[edit]

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 topsoil to one part compost.[8]

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 by treading with a boot as it is filled in. However, do not be so rough that the delicate root haris are damaged,[8] and the soil is compacted, preventing water and air circulation.[7] 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.

Feeding[edit]

Watering[edit]

Protecting[edit]

References[edit]

See also[edit]

External links[edit]