Just to add some more information to your comment, I'm an Architect and I worked on a building with trees growing on top of a structure, but not at high level.

Just to add some more information to your comment, I'm an Architect and I worked on a building with trees growing on top of a structure, but not at high level. I just happen to know that, according to the tree specialist, a 5-8m tall magnolia tree can probably survive in a cube of soil 1.5m x 1.5m x 1.5m encased in a concrete pit lined with a geotextile to prevent root damage to the structure. It needs to be hooked up to a fairly sophisticated hydroponic system to keep it alive and their growth will be stunted by the restrictions placed on the root ball. Another issue with some of the trees shown is that, because they are under the structure, they will need to be turned every couple of years and/or illuminated with special lights to keep them from being distorted by growing towards the sun and to ensure they receive enough light to photosynthesise. More generally, the computer renderings you see in the article are often generated by students or outside design agencies based on sketches and other early information from the architects. They are done in a few weeks often to very tight deadlines and are definitely not based on technical drawings so you can get all kinds of weird stuff in there depending on how imaginative the computer graphics person is and how late they had to stay up to beat the deadline. A real skyscraper takes years to design, the details of how tree pits work wont be fully bottomed out until a few years after the fancy renderings are done. Ultimately, trees often disappear from the finished product once it has permission from the city as the developer will be looking for ways to cut costs; things like this often get the chop unless there are specific conditions to keep them in the design that have been placed on the permission granted by the local authority.