Hi all - I have a "tree" in my garden which looks quite shrubby (there are about 6-8 stems all originating from the same spot) but is about 4 metres tall and some of the stems are about 3-4 inches wide. I've seen what looks like a less woody version of the same plant growing as a hedge nearby. I've attached a photo of some leaves and flowers. Does anyone know what this is and whether it can be classed as a tree, or is it an overgrown shrub?
I suggest you look upon tree/shrub/etc not as large categories that are subdivided in to particular plants.
Rather, look upon those terms as habits that plants can take.
In that way a particular plant can be both shrub and tree, depending on how it is grown in a garden or park (or how it grows in the wild, where it is subject to the shaping forces of the wind, browsing animals, shading, disease and pests, etc.)
Common privet is most commonly grown as a hedge, but what sometimes happens is a hedge gets neglected and overgrown, then somebody (perhaps a new owner) comes along and tidies things up. By that time, it is quite possible that one of the individuals from the original hedge has grown into a tree, and seems (to the new gardener) to be worth saving, even if the rest of the hedge is not wanted. With a bit of pruning, it can be made into a respectable specimen tree. It may never have the stature and stage-presence of an oak or beech, say, but it can grow as a single-stemmed plant, ie. tree, in its own way.