Despite countless architectural renderings to the contrary, the top of a skyscraper is actually a terrible place for trees. Tim de Chant breaks down all the reasons in Arch Daily, citing brutal winds that buckle tree trunks and disrupt the fragile layer of air around leaves. They'll also have to contend with extreme temperature shifts and the simple logistics of keeping a plant fertilized on the 23rd floor. As a result, sky gardens are usually the first thing purged from building proposals once the cost-cutting starts. You might see a lot of them in sci-fi sketches, but we until engineer a hardier tree, you'll find very few in real life.