Planting Fruit Trees: The Crucial Graft Union Mistake

Anyone planting an apple, cherry or apricot tree in spring imagines fragrant blossom and baskets filled with home-grown fruit. Yet in reality, the tree often remains stunted and produces few, if any, flowers. This is rarely due to a “poor variety”; almost always, the same planting mistake is responsible: the trunk has been positioned at the wrong depth in the soil.

The inconspicuous trunk area that determines blossom or disappointment

Fruit trees bought from a nursery are almost always grafted. This means the desired variety grows above, while a hardy rootstock forms the lower part. The join between these two sections is the most sensitive point on the entire tree - and it is precisely this area that is often buried during planting.

“Covering the graft union with soil deprives the fruit tree of air, vigour and the basis for early, abundant blossom.”

To understand exactly which part may go into the soil when planting and which must remain above it, look closely at the lower section of the trunk.

Root collar and graft union: how to identify the vital boundary

Two areas sit close together at the base of the trunk:

• Root collar: the transition between the roots and the actual trunk, usually slightly swollen and often discoloured near soil level.
• Graft union: a noticeable bulge, bend or scar-like swelling a few centimetres above the root collar.

From the root collar upwards begins the section of the tree that must not remain permanently below ground. This is where many gardeners go wrong: they heap plenty of soil around the trunk, often covering even the swelling at the graft union. Although this may seem stable and “protective”, it is extremely dangerous for the tree.

Why planting fruit trees too deeply can effectively suffocate them

Constant moisture around the trunk creates ideal conditions for fungi

The bark on the trunk is not designed to sit continually in damp soil. Unlike roots, it reacts badly to persistent moisture. As a result, the bark starts to rot, initially out of sight beneath the ground.

For a while, the tree may still appear normal from the outside, but internally the following takes place:

• Moisture accumulates around the trunk.
• Fungi enter the softened bark.
• The vessels that carry water and nutrients are gradually destroyed.

The trunk rots from the base upwards before the gardener notices the damage. The crown receives too little nourishment, shoots remain thin and hardly any flower buds develop.

When the grafted variety produces its own roots - and the tree loses its benefits

Covering the graft union with soil often causes another problem: the upper, “grafted” variety begins to form roots of its own. At first, this may sound like extra stability, but it comes at a high cost.

“As soon as the grafted variety forms its own roots, the tree loses the beneficial characteristics of the hardy rootstock - it becomes more susceptible and fruits much later.”

The carefully chosen rootstock is intended to provide:

• better adaptation to the soil,