Planting mature trees: from rootball to adaptation

Planting a mature tree is an operation that begins before the lorry arrives. The specimen, the rootball, the access, the lifting equipment and the ground all have to be coordinated. When these decisions are left for the day of unloading, the risk increases of damaging the tree or of planting it in a soil that cannot receive the roots.

At Diaplant, the main dispatch season runs from November to April, during the dormancy of most species. Planting nevertheless remains dependent on the weather, the state of the soil and the characteristics of each tree.

Before lifting, the exact position should be settled. The future crown, the distance from buildings, the wind, the drainage and the crane access all influence the choice.

A check is also made for underground services, foundations or compacted layers. Setting out done only at the surface can hide conflicts that appear when the planting hole is dug.

The design should indicate the desired orientation of the crown. With an asymmetric specimen, turning the tree can change the result considerably.

As a minimum reference, Diaplant recommends cultivating and decompacting the soil in width and depth to at least twice the dimensions of the rootball. Each case is adjusted to the texture, the drainage, the size of the tree and the needs of the species.

In a deep agricultural soil that has already been worked, the intervention can be more restrained. On compacted platforms or fill, it is worth preparing a larger volume and creating continuity with the surrounding ground. For a large tree of medium maturity, about 8 m³ — 2 × 2 × 2 m — can serve as a reference where the site allows.

These measurements refer to the prepared soil. The tree is still placed with the root collar at finished ground level, or slightly above when technically justified. The greater the volume of functional, aerated soil, the better adaptation and growth tend to be, provided the base stays stable and the water can drain.

Before the rootball is placed, you need to understand how water moves through the ground. A planting hole dug in compact soil can act as a container.

If the water is slow to disappear, the solution is not to hide the problem with a layer of gravel at the bottom. It may be necessary to change the ground modelling, create working drainage, decompact at the sides or reconsider the species.

The aim is to let water in and out without leaving the roots either dry or permanently saturated.

The slinging system depends on the form, the weight and the proportion between crown and rootball.

Younger, lighter trees can be lifted by the trunk with specialist padded slings, positioned to balance the centre of mass. With multi-stems and shrubs, the slings can go round the rootball without compressing it, with a second support on a trunk or structural branch to stabilise the tilt.

With very large trees, the main load is carried at the rootball and the support on the trunk serves to control rotation and levelling. Special forms may need dedicated equipment.

The tree is oriented and set down while the crane still holds part of the load, so that the position can be corrected before backfilling.

The rootballs prepared by Diaplant are wrapped in hessian and wire mesh from specialist suppliers, with biodegradability certification.

We do not recommend removing or loosening these materials. The team compacts and wraps the rootball to preserve its cohesion. Opening the mesh can cause cracks, loss of soil and the root mass breaking apart.

This guidance applies to the method and materials used by Diaplant. Trees from another source should be assessed according to their own specification.

The surface of the rootball should not automatically be taken as the reference. The root collar needs to be located at the trunk.

Planting too deep reduces aeration at the base and can keep trunk tissue in contact with wet soil. Planting too high leaves part of the rootball exposed and increases drying.

After settlement, the level is confirmed, bearing in mind that the ground may sink slightly.

The soil is spread around the rootball, without aggressive compaction. The first watering is deep: it settles the ground, reduces air pockets and creates contact between the soil and the root mass.

As a general rule, Diaplant applies a slow-release NPK fertiliser at this stage, at a rate adjusted to the specimen and the soil. Feeding supports the first growing season, but it does not replace water, drainage or the correct level of the root collar.

In the days that follow, small inspection points of about 20 cm help to show whether the water is passing through the rootball and whether the soil is regaining oxygen.

The system depends on the size, the crown, whether the foliage is evergreen or deciduous, and the exposure to wind.

Up to a girth of 20–25 cm, double staking with treated pine stakes is common. For larger sizes, triple staking may be used and, as a guide from 40–50 cm, oblique systems with steel cables. These limits are not hard and fast.

Underground anchoring can complement above-ground systems, secure multi-stems and shrubs or allow an immediate finish with no visible stakes.

The ties should stabilise without strangling the trunk and need inspecting.

The first year is critical. Watering should be deep, with enough volume to wet the whole rootball, and spaced according to the drainage, the species and the climate.

In the second year, attention remains important during the hottest periods. As the roots occupy the surrounding ground, the tree becomes less dependent on the initial volume.

Monitoring may include visits, photographic records and contact with the team whenever atypical symptoms appear.

• European Tree Planting Standard.
• Technical literature on establishment and nursery production systems.