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:
Chamaecyparis obtusa 'Well's Special'
Cryptomeria japonica 'Globosa Nana'
Magnolia yuyuanensis, Pick Up ONLY
Mahonia 'Beijing Beauty'
Osmanthus fragrans 'Tea Olive'
Pieris japonica 'Temple Bells'