Another Viburnum that is worth looking at is the locally produced Viburnum
plicatum f. tomentosum 'Summer Snowflake' and Viburnum plicatum mariesii.

The Rhododendron Species Foundation garden has a huge mariesii (I think) that
will be looking very good very soon now. I'll be down next weekend and if it is
out in bloom I'll post a picture. Stunning, if you have the room.