Planting trees

The right time to plant a tree is during the dormancy period. In the case of deciduous trees this lasts from the moment the trees lose their leaves naturally and have hardened off until the moment the sap flow starts again in spring. In Western Europe, trees with root balls can generally be planted from mid-November to late April, although this depends strongly on the climatic conditions and the species of tree. The temperature in autumn and spring plays a key role and not all trees drop their leaves at the same moment. The same applies to the time that the leaf develops. For evergreens and conifers the planting season is usually slightly longer than it is for deciduous trees. Container grown trees can be planted all year round. These are generally smaller sizes of trees.

Planting in autumn is ideal
The re-growth of the tree, i.e. whether it starts developing new hair roots, depends on several different factors such as the moisture content and temperature of the soil. In autumn these factors are generally favourable. The temperature of the soil is still high enough for the trees to develop new hair roots after transplanting but before the winter sets in. By increasing the number of hair roots, water absorption in spring is made easier. Trees are less affected by transplantation stress and growth resumes more quickly. Planting in autumn is the most suitable time for the trees, although in practice this is not always feasible.

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Tree Planting: A Complete Step-by-Step Guide

In this guide, you'll learn how to plant trees efficiently and effectively. From creating the planting hole to pruning after planting, we cover everything you need to know to ensure newly planted trees thrive and grow robustly in the future. This guide provides the information needed to successfully plant trees.

1. Tree Planting: Creating the Planting Hole

Create a spacious planting hole, 1.5 to 2 times the diameter of the root ball. e.g., if the tree has a 60 cm diameter root ball, the planting hole should be at least 90 cm in diameter, but preferably 120 cm. Make the planting hole slightly less deep than the root ball's height. To ensure proper oxygen exchange, the tree must not be planted deeper than it stood at the nursery! For large trees, take into account the settling of the tree due to the weight of the root ball, which can compress the soil beneath, especially if the ground has not yet settled, e.g., in new construction projects (fig.1). Loosen the bottom of the planting hole to a depth of one spade, and if necessary, also loosen the sides. Walls of clay or loam soils can become compacted when wet during digging. Loosening them with a spade allows roots to grow through more easily. Mix any new soil with the existing soil. Sometimes the hole is filled with garden soil. Mix it at the bottom with the existing soil so that roots can easily grow from the planting hole.

2. Tree Planting: Anchoring Trees

A newly planted tree needs to be anchored to prevent it from leaning. The most common anchoring method uses two or three stakes. Two stakes are sufficient for smaller trees, up to a trunk circumference of 25-30cm. Larger trees, with a trunk circumference from 25-30cm, should preferably be planted with three stakes. Choose stakes with a length and thickness appropriate for the size of the tree. For standard trees, with a free trunk height of at least 200 cm, use 250 cm tree stakes. 100 cm goes into the ground and 150 cm remains above. For shorter trunk lengths, choose a shorter stake.

Drill 2 or 3 holes in the ground next to the root ball with a ground auger, opposite each other or in a triangular pattern, and drive the tree stakes firmly into the ground. At least half of the stakes should be underground. When using 2 stakes, consider the most common wind direction. In the Netherlands, that's the southwest wind. In that case, place the stakes southeast and northwest. Fill the planting hole with soil. Soil life can be stimulated by mixing an organic soil improver or well-decomposed compost into the soil. Firmly compact the soil in the planting hole intermittently. Connect the top of the three tree stakes with slats for a solid bond.

This is not necessary when using two stakes. Wrap a tree strap around the trunk from each stake and nail it to the tree stake. The tree straps should not be loose but should also not be under tension. After about 3 years, the tree stakes will have deteriorated and can be removed (above-ground part). The tree will have rooted firmly enough to grow without support.

3. Tree Planting: Applying a Watering Ring

New trees need extra water for at least the first two years. The amount depends on the weather and the type of tree. Use a soil or plastic watering ring to ensure the water seeps well into the root ball. The diameter of the watering ring should match that of the root ball, so the water also penetrates the root ball (figure 5). Check the soil moisture next to the root ball once a week during dry weather and water as needed. When water is needed, give a large amount at once instead of a little every day. Checking soil moisture can be done, for example, with a soil probe or by inserting a spade into the ground. Keep the root balls moist throughout the growing season, but not soaking wet! Trees can also die from too much water, as this causes too little oxygen in the soil and the roots to rot. Besides a watering ring, there are also other methods for watering trees.

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Pruning After Planting

Healthy trees possess a natural balance between crown and roots, which is disturbed the moment the tree is transplanted because every tree inevitably loses some of its roots during digging. The roots are then less able to supply water to the crown, causing stress. The tree will respond by producing less and smaller leaves, thus reducing its leaf surface area. When the water shortage is too severe, the tree will even begin to shed wood from the crown, risking damage to its habit. Watering is therefore necessary for the first two years, but this alone is often not enough. During long warm periods, or at extremely high temperatures, it may happen that the leaves dry out while the root ball remains moist. The root capacity is simply not sufficient to transport the required amount of water to the crown. Giving more water in this case is not an option and only leads to adverse consequences such as oxygen deficiency and root rot. The only solution is to reduce the demand for water by pruning the tree, preferably right after planting, to prevent the trees from suffering during peak periods. In the first two years, the crowns will have less volume, but the trees will experience less stress, root more quickly, and then develop better.

Pruning is done on the one- or two-year-old wood. The thick wood in the crown should be retained. It contains reserve food that the tree needs to develop new roots. It is not necessary to prune all the present one- and two-year-old wood from the tree. Trees with a lot of wood in the crown need a significant pruning, but trees with little wood in the crown, such as an Ailanthus, are minimally pruned. To not damage the habit of the tree, it is wise to keep the terminal buds and only remove side shoots.

Trunk Protection Against Sunburn

Unfortunately, it is becoming increasingly common; cracks on the trunk due to overheating. Normally, the transport of water in the trunk protects the bark cells against overheating, but after planting, less water is transported to the crown and this cooling system is not sufficient. The trunk therefore risks sunburn. The setting sun is the worst offender because it shines directly on the trunk and can heat the cells to the point of breaking. This is why sunburn is usually visible on the west side of the tree.
Especially trees with a smooth and thin bark are very vulnerable and need to be protected. This can be done by wrapping the trunk with coconut or reed mats. Trees with a rough bark and trees that are branched from the base are less vulnerable and usually do not need protection.

Attention: wrapping burlap around the trunk was often done in the past, but experience has shown that this can have adverse effects. Because the burlap is wrapped tightly around the trunk, it can ferment underneath. The temperature can then rise significantly, with negative consequences for the bark and the rest of the tree.