This is Snowball Viburnum Opulus, it is also known as The Snowball Plant.
So many people mistake it for a Hydrangea. They say it grows 10-15 feet tall and wide, but I have a feeling in some areas it may be larger. It is great as a backdrop in your border gardens and cuts well. In one of the pictures on the left you can see how the snowball start out, it does not begin to leaf out until the snowballs are formed and blooming and then after they drop it begins to fill in with more leaves. My particular plant blooms on old wood.