The National Park Service just put out a booklet entitled Plant Invaders of Mid Atlantic Areas. In it, page 50 says that the types developed to try to respond to branch problems have cross pollinated with the original bradford and these new trees are aggressively spreading into disturbed natural areas. The quote is "New hybrids produce viable seeds through cross pollination with the Bradford cultivar".
Those who are not fond of this tree would relish the descriptions of what should be done: the relatively mild pulling of seedlings from moist soil, to pulling out small trees with a Weed Wrench, to cutting down/stump treatment or girdling large trees.
