What shrub is this?

Answer

Dear Jürgen,

The plant in the photo is a young specimen of Magnolia grandiflora, an evergreen tree native to the southeastern United States. The plant is often planted as an avenue tree in France and further south. But in recent years you have also seen it more often in our gardens. So you can certainly order one from Belgian tree nurseries or garden centres. Make sure that it is planted somewhat sheltered and out of the wind, because heavy frost can sometimes be a problem, especially with young plants.