Preparing the planting hole
The correct dimensions for a planting hole are at least one time as wide as the root ball and equally as deep as the height of the root ball. A planting hole must be dug carefully. This is usually done mechanically, in which case it is important that the sides of the planting hole are not cut smooth. Especially in wet soil and in clay- or loam-rich soils, the sides can quickly become smeared, preventing new roots from penetrating them. In that case, the sides of the planting hole must be loosened.
If the planting hole is made with an excavator, a toothed bucket is preferred to prevent smearing. The bottom of the planting hole must be properly loosened to allow deeper rooting and to promote the capillary rise of groundwater. The loosened layer should then be firmed again to prevent excessive settling of the soil - and therefore of the tree. Do note that digging must never go below the highest groundwater level; always remain at least fifteen centimetres above it.