Planting Trees: A Guide
As a garden designer I am often asked about the best way of planting trees. The main points to consider when choosing and planting trees are root health, weather, soil conditions and maintenance. Attention to these details will enable a healthy tree to establish more quickly.
When to Plant
The best time for planting trees is between October and April when the roots are dormant. However, containerised trees will need more care if planted during the spring and summer when there is likely to be a soil moisture deficit. Watering containerised trees during the growing season is essential to long term successful establishment. Bare-root and root-balled trees are only available during autumn and winter. It is important that the roots do not dry out and should therefore be planted immediately or heeled-in to a temporary position awaiting final planting.
It is unwise to plant in waterlogged conditions where water is pooling on the surface of the ground or lying within the planting hole. Nor is it wise to plant in frozen conditions.
Site preparation aims to improve the condition of the soil addressing issues such as compaction, drainage and structure.
- Loosen the soil to a depth the same height as the root ball and over a wide area to improve drainage and relieve compaction.
- Add organic matter to sandy or clay soils to improve structure.
- Dig a planting hole that is as deep as the roots, and at least three times the diameter of the tree’s root system. When planting in grassy areas mowing is easier around a circular planting hole, however root penetration is better in square planting holes. Therefore a square planting hole within a mowing circle is best.
- In order for the roots to develop and explore the soil there should be no compaction in the sides of the planting hole. Use a fork to loosen the sides.
- A soil that becomes regularly waterlogged in winter will need special consideration. Either plant trees that have adapted to thrive in wet conditions, install drainage or plant on a mound (around 25-30cm high by 1m diameter).
- Firstly ensure that the tree’s root zone is moist before planting. Soak bare-rooted trees for at least half an hour before planting and water containerised trees well.
- Don’t forget to remove any nursery labels and check for damaged branches before planting.
- Trim pot bound roots, however there is no need to trim or tease out roots from root balls that are not pot bound. Tease out the roots of bare rooted trees to check the spread.
It is unnecessary to add fertiliser when planting trees. A dusting of an inoculant of mycorrhizal fungi over the roots may help trees establish if the soil is poor. Adding extra organic matter to the bottom of the planting hole is also unnecessary and may cause the plant to sink as it decomposes thereby hindering successful establishment.
- Take the tree out of the container or remove fabric wrapping. Some specimen trees specify that the wrapping be left on under the terms of their guarantee however the fabric wrapping should be removed if this is not the case.
- Position the tree in the planting hole so that the topmost flare of roots is level with the surface of the soil. If the tree is a large specimen or top heavy it will need staking at this stage of planting before backfilling the planting hole.
- Avoid deep planting because this prevents necessary air movement to the root zone and makes the lower trunk vulnerable to disease leading to poor establishment. At this stage check that the tree is upright, do this from different angles ideally with the help of a friend.
- Refill the planting hole carefully, placing soil between and around all the roots firming gently as you go to eliminate any air pockets. Avoid compacting the soil into a hard mass because this will restrict air movement in the root zone.
One of the most common causes of failure in newly planted trees is drought stress. Dry and windy weather can cause water shortages even during a cool summer. Soil below ground may still be dry even if the soil around the base of the tree looks moist. Regular watering is therefore essential to healthy establishment.
During the growing season a tree will need 4-6 watering cans (30-50 litres per square metre) per week. The amount needed depends on the soil type. It is possible to over water which leads to rotting roots. This can happen on poor draining soils and with automatic watering systems. If unsure dig down the side of the trees root zone to see if the soil is drying before watering.
Weeds compete for water and nutrients intercepting them before they reach the trees roots. Therefore, maintaining a weed free circle which measures at least 1.2m in diameter around the base of the tree for its first three years is recommended. There are several ways to achieve this. Mulching is a highly effective method with a choice of organic or synthetic materials. When applying mulch be sure to leave a gap of 10cm around the tree’s trunk to avoid the risk of damaging the bark. Other options are hoeing and the use of contact or systemic herbicides.
Newly planted trees do not need feeding until their first season of growth if the soil is poor or the tree needs a boost. However, if mycorrhizal fungi has been applied fertilizer should not be used. This is because the chemical phosphorous, which is found in fertilisers, suppresses the fungus.
Carry out formative and corrective pruning when the tree is still young. Check for competing leaders and remove or shorten them. In addition, remove wood that is damaged, diseased or dead. Remove the trees side-shoots in stages over several seasons if a clear trunk is what you want to achieve.
Staking protects the tree from windrock in windy conditions which can cause damage to the root ball. Check stakes and ties twice yearly in spring and autumn. Adjust ties as the tree grows to avoid damage to the trunk. Remove the stake after two years once the tree has established.
Tree guards may be necessary to protect the tree from wildlife such as deer and rabbits.
In conclusion, following this simple guide will give your newly planted tree or trees the best start possible.
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