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:
Aesculus flava, Yellow Buckeye
Cephalotaxus harringtonia 'Duke Gardens'
Cephalotaxus harringtonia 'Fritz Huber'
Cephalotaxus harringtonia 'Gold Rush'
Gardenia jasminoides 'Crown Jewel'
Osmanthus heterophyllus 'Goshiki'