Pollarding

Pollarding is actually an ancient technique for the production of amenity timber. However, it also affords a secondary benefit in cyclical management (typically seen on street trees) or the introduction of a new framework in the scaffold limbs. This helps to promote the development of a more compact crown and impede explorative root growth.

By Albert kok - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2915334