That looks like the blossom from a flowering pear tree (Callery Pear) - Pyrus Calleryana. We have several out front of our house. They are naive to China and were brought here as ornamental trees. Since they don't produce fruit from among their own genus they were thought to be quite safe for the environment. Unfortunately, as they became more popular other types were brought over which had enough genetic variety to hybridize - allowing it to overcome it's natural sterility. Now many of those trees produce little hard fruits that birds and squirrels distribute around into the wild, turning the once beautiful ornament into a terrible environmental pest. Now no one know what to do with them as they produce huge wild thickets in places no one wants them.
Thank you Strad and AuntiPode. This "shrub" is so beautiful when it is in full bloom but is a real nuisance the rest of the year. I'll cut it back to almost ground level but it keeps coming right back next spring. Don't remember any fruit but I'll certainly pay more attention now.
