Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Large seedlings that resulted from crosses between Bradford pear and other Callery pear cultivars are easy to spot --thickets of these white-flowered invasive species are in full bloom across the state. Bradford pear itself is self-sterile, it was selected from Asian seedlings grown in this country for its extreme success as a street tree that would flower its head off but produce no messy fruit to litter the street or attract wasps. But USDA growers kept introducing other Asian Callery pears and soon viable seeds were setting and resulted in many plants that expressed traits of the wild types – four-inch long extraordinarily strong thorns on their trunks and branches. These plants are practically pest free. In the upstate, a field left fallow for even a year can be made unusable by the rapid invasion of these armed and destructive seedlings.