I set out 3 small trees a year and a half ago, 18 to 24 inches tall. I planted them in the back of a bed that had really good soil. Since then they've grown to 15 feet, and have sent out a very aggressive root system. I'd really like to know what these things are. This is the first time they have bloomed. Very pretty trees, but seem to be very intrusive. Any help greatly appreciated.