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:
Abelia chinensis 'Compact'
Asimina triloba, Paw Paw
Chaenomeles x 'Bonita'
Edgeworthia chrysantha 'Snow Cream'
Gardenia jasminoides 'Crown Jewel'
Magnolia macrophylla var asheii
Magnolia x loebneri 'Donna'