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 x 'Canyon Creek'
Cyrilla racemosa 'Spring Cloud'
Hydrangea luteovenosa 'Aureovariegata'
Rhododendron stenopetalum 'Linearifolium'