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
Asimina triloba, Paw Paw
Cryptomeria japonica 'Golden Promise'
Fagus grandifolia, American Beech
Gardenia jasminoides 'Kaleidoscope'
Hydrangea macrophylla 'Blaumeise'
Mahonia eurybracteata 'Narihira'