Planting period

As long as you do not have frost, you can plant trees and shrub from early autumn. 
Bare-root trees can be planted at the end of Winter or early Spring when the ground is not frozen so new growth can begin.

Trees and roses with pot roots can be planted up into summer. Ensure sufficient watering when planting or transplanting.

Shrub and Tree Roots | Planting Period
Bare-root trees and roses | August to September
Trees with peat or balled roots | September to October
Trees and roses with pot roots | December until end January

The advantage of planting in spring

Except for bare-rooted roses, spring planting can be recommended for all those plants which are rather sensitive to frost. These are, for example, many evergreen plants such as the rhododendron, box, cherry laurel and photinia, but also some deciduous plants such as the rose mallow, hortensia and lavender. If we give such plants a whole garden season to grow their root systems, they can withstand their first cold period much better than if they are planted just before the onset of winter. In general, all frost-resistant shrubs and trees are best planted from the end of March until the end of June as long as the ground is not frozen and not too wet. Autumn planting means that the plants can develop their root systems until spring, and then start with a growth advantage. They therefore develop better than plants which were not planted until spring.

Larger trees
Autumn planting is also expedient for larger trees. Trees are already starting to grow at this point. 
In particular in winter, tree bark heats up very unevenly in the sun’s rays. In order to counter the risk of tension cracks in freshly planted trees through major temperature differences between sunny and shady sides, trees planted in autumn must be wrapped in thin linen fabric. This also protects the plants against severe water loss.