I planted four Japanese Snowball bushes in 2006 that I ordered from Greenwood Nursery. (Wow, their prices have really gone up since then.) It didn't take me four years to realize that the flat-headed "lacecap" flowers on my shrubs do not look like the fluffy white rounded snowball heads of the shrubs on the Greenwood Nursery website!
So I set out to find an explanation. I consulted the trusty Internet before contacting Greenwood Nursery, as I have called Greenwood with questions/problems in the past, and to be honest, they haven't established a good reputation with me for their customer service.
I did a google image search for "japanese snowball" and found shrubs with various flowers, but all sharing the same arrow-shaped leaf. Apparently these shrubs are all different varieties of the genus "Viburnum." With over 150 species, I decided to give up trying to conclusively identify my viburnum and resorted to emailing Greenwood to draw the issue to their attention. They have not responded to my query.
While it's not the plant I thought I was getting, it's still a lovely shrub. The Greenwood website claims the plant flowers Spring, Summer and Fall (which is one reason I was drawn to it), but they're fibbers, as it only blooms in the Spring. I have no idea how tall it will be at maturity, but it is currently 5'. I'm hoping it doesn't get much taller, as it fits into this setting very nicely. Perhaps it wouldn't mind a little pruning in the Fall.
Read this fantastic article from finegardening.com for a more in-depth discussion of viburnum.