Appearance Bradford pear is a cultivar of Pyrus calleryana. It is a deciduous tree that can grow up to 60 ft. (18 m) in height and 2 ft. (0.6 m) in diameter. Foliage The leaves are alternate, simple, 2-3 in. (5.1-7.6 cm) long, petiolate, and shiny with wavy, slightly toothed margins. Flower Flowering occurs early in the spring (April to May) before the leaves emerge. The flowers are 1 in. (2.5 cm) wide, showy, malodorous, and white. It is insect pollinated. Fruit Fruits are round, 0.5 in. (1.3 cm) in diameter and green to brown in color. Ecological Threat Pyrus calleryana 'Bradford', produce sterile fruits because they do not self-pollinate. They have been widely planted throughout the United States since the early 1960s as an ornamental. New cultivars of Pyrus calleryana were bred to reduce the tree's tendency to split in snow or high winds. The Bradford pear cultivar, other P. calleryana cultivars and P. betulifolia or Asian pear, can hybridize and produce fertile fruit. In addition to this, fertile pear varieties are commonly used as the rootstock when grafting. If the grafted crown is damaged the fertile rootstock can them dominate, producing fertile fruit. These factors and others may have contributed to the trees seeding out into natural areas and becoming an invasive problem.