The line between whether a plant is a "tree" or a "shrub" is sometimes very thin and quite blurry! We use the following criteria to decide which type applies to a certain plant:
Buxus sempervirens 'Unraveled'
Cedrus deodara 'Feelin Blue'
Chamaecyparis obtusa 'Confucius'
Cryptomeria japonica 'Golden Promise'
Diospyros rhombifolia, Diamond-leaf Persimmon
Ilex crenata 'Piccolo', Dwarf Japanese Holly