It's a big oval creature, whether you consider it a shrub or tree is up to you. They tend to grow 10-20' tall and often two-thirds as wide. On the eastern end of Long Island they bloom late April. As you can see the white five-petaled flowers are fantastic, and this year very prolific.
When the flowers pass it begins to leaf-out with the three-part leaves from which it gets it's specific epithet, trifoliata. Ultimately it's a gnarly, thorny thing that requires a lot of maintenance to be kept really picture perfect but just the same I love it.
The thorns and hardy acidic fruit make it a fun conversation piece here in our Zone 6b or 7a. It's safely hardy in Zones 6-9. Native to China and Korea it was introduced to the US around 1850.