Post-transplant stress: expected symptoms and warning signs

After planting, the tree needs to rebuild the relationship between root and crown. Part of the root system stayed in the nursery, the soil has changed and the plant is still exposed to wind, heat and variations in water.

Some reduction in growth can be part of adaptation. Persistent wilting, progressive dieback of branches or instability should not be treated as normal without checking.

The symptoms alone do not identify the cause. Lack of water and waterlogging can produce similar leaves.

The available root is mostly inside the rootball. Until it grows into the surrounding ground, the tree depends on a small volume to supply a mature crown.

Transport and the change of exposure add stress. A trunk that was previously protected may receive direct sun; the crown may be more exposed to the wind.

The tree reduces growth, closes its stomata and uses reserves. This temporary response is not necessarily disease.

Shorter growth, slightly smaller leaves and some partial leaf drop may appear during establishment.

The intensity varies. Birches can lose their leaves quickly when short of water. Magnolias wilt easily. Some species keep a stable appearance for weeks and reveal problems only in the heat.

The season influences the reading. A deciduous tree planted in winter does not show its full response until bud break.

The rootball is dry at depth, the leaf loses turgor in the hottest periods and the margins dry out.

The surface may be wet from a short watering. Inspection points need to be opened and the interior checked.

Blocked drippers, emitters set too far away or light rain are common causes of false security.

The correction should wet the volume without moving into continuous saturation.

The soil stays sticky and saturated for a long time, and there is an anaerobic smell or water standing in the planting hole.

The root loses oxygen and stops absorbing properly. The crown wilts even though water is present.

Increasing the frequency makes the problem worse. First the inflow is reduced and the drainage failure identified.

One part of the rootball may be dry and another saturated, so the check is made at several points.

A tree planted too deep can look normal and lose vigour progressively.

Check whether the root collar remains visible and whether the ground has settled.

Mulch, soil or lawn should not cover the base.

When the mistake is recent, repositioning can be safer than waiting for serious symptoms.

A rootball that has lost cohesion leaves roots exposed and reduces contact with the soil.

Knocks to the trunk, broken branches and damaged graft unions also affect recovery.

The initial inspection and the photographs taken at unloading help to tell earlier damage from later problems.

If the rootball rotates in the wind, the new roots break and establishment slows.

Straps that are too tight cause wounds and deformation. Loose stakes no longer do their job.

The staking is observed together with the crown. A mechanical problem may be the cause of symptoms that look physiological.

A tree that grew sheltered may end up with its trunk directly exposed to the sun.

Sunken areas, discolouration and cracks on one side of the trunk may indicate sunscald. The damage becomes visible some time later.

The orientation marked at the nursery and breathable protection reduce the risk.

Stress can make the tree more susceptible, but the presence of a fungus or insect does not prove that it is the main cause.

The distribution of the symptoms, specific signs and their development are looked for. Where necessary, a sample is sent for diagnosis.

Applying a product without identifying the problem can delay the correction of watering or soil.

Progressive dieback of main branches, general discolouration, oozing, lesions at the base, instability or a complete absence of new growth at the right season call for assessment.

The rapid loss of much of the crown should not be followed only from a distance either.

Photographs help with triage, but they do not measure moisture, drainage or root.

The initial condition, the watering programme, the rainfall and any changes are recorded.

The photographs should include the whole tree, details, the root collar, the soil and the staking. A picture of a single leaf provides little information.

In the first year, the frequency of observation increases in hot periods. The second year remains important until the root occupies a greater volume.

When a symptom appears, it is common to change the watering, repeat the fertiliser and prune all at the same time.

This combination makes it impossible to understand the cause and can make the tree worse. The initial feed with slow-release NPK may be part of planting; further applications should only go ahead after soil, water, depth and stability have been confirmed.

Adaptation takes time. Monitoring should not confuse patience with an absence of diagnosis.

• How to water a mature tree in its first year
• What a photograph can diagnose
• How to monitor adaptation

1. Allen, K. S. et al. (2017). Review of production systems and the survival of urban trees.
2. European Arboricultural Standards. European Tree Planting Standard.
3. Literature on transplant shock and tree establishment.
4. Diaplant’s post-planting monitoring method.