First of all, roof gardens create space for greenery in urban areas. In addition, roof gardens and green facades make a significant contribution to capturing particulate matter, they improve the ecology and they reduce the Urban Heat Island effect. This improves the microclimate in cities. 

Almost every type of tree can be planted on roofs and in containers but some types are more suitable than others. A tree with aggressive roots will need good protection underground to make sure the roofing material is not damaged. Tolerance to wind is also an important consideration in the choice of species. It is not advisable to choose a species that suffers with broken branches in strong winds for use on a roof.

The shape also needs to be taken into account: standard trees are less suitable than multi-stems or topiary trees. Standard trees have a much higher centre of gravity, which increases the risk that they will blow over or break. If a large branch breaks the crown will be affected and the damage will almost always be visible. Topiary trees are less heavy as the crown is pruned back every year. If a branch breaks from a topiary tree crown, the damage will be repaired by the next year. The planting advisors at Ebben Nurseries will be happy to help you in your choice of species.

Trees on roofs and in containers face more extreme conditions: the wind levels are higher and the temperatures vary more than at ground level. In containers, the growth space is also very limited and a good substrate with added nutrients and water is indispensable. The location plays an important role on roofs. There are often more possibilities on parking roofs. Due to the stronger construction of parking roofs, they can bear more weight. The situation at ground level makes the wind and temperatures less extreme. Of course the budget for maintenance is important when choosing trees on roofs or in containers. A tree on a roof or in a container lives in unique conditions and requires more maintenance than a tree in open ground.

Multi-stem trees are the most suitable for roofs. This is because multi-stem trees have a low centre of gravity as a result of the weight of the multiple stems. In the event of wind damage to the crown, the tree retains its characteristic multi-stem shape. Also, with a multi-stem tree much more is visible at eye level, so that the perception of it is much greater. Multi-stem trees are available in very many varieties, shapes and dimensions.