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'
Ilex aquifolia 'Night Glow' Pick Up ONLY
Illicium parviflorum 'Florida Sunshine'
Magnolia x 'Stellar Ruby'
Osmanthus heterophyllus 'Porcupine'