"Don’t think you can plant trees in containers? Think again. These birch trees are placed in large containers, and because the root ball is kept from growing outward, the whole tree remains smaller and more manageable."
Pleached Hornbeam trees - Pleaching is the weaving branches of multiple trees together for privacy, wind & sound block. Best trees for pleaching are Lindens, Hornbeam (Carpinus betulus), Beech, Apple, Pear, Hawthorn, & Carob. The American Hornbeam (Carpinus Caroliniana) is hardy and holds some of it's leaves during winter to provide a privacy screen year round. Because each tree is trained to have a single stem, there is space below a pleached hedge for other plantings (a hedge on stilts!)