Callery pear is a small to medium-sized tree with a compact, symmetrical, pyramidal or columnar shape that spreads to become oval with age. Many cultivars exist with slightly different characteristics; all contribute to the species' invasiveness.
Leaves are alternate, simple, generally oval, to 3 inches long, with rounded teeth, glossy green, turning orange, gold, red, pink, and/or purple in fall. Some cultivars develop patterns of colored circles and spots in autumn. Leaves bob in the wind on long leaf stems.
Bark is gray-brown, smooth on young trees, splitting into scales with age.
Twigs are thornless in cultivated trees, but in wild types (including trees that develop from sprouts of a tree that was felled), the twigs end in thorns.
Flowers in early spring; abundant clusters of white flowers, 5-petaled, each to ¾ inch wide, unpleasant-smelling.
Fruits like tiny, hard apples, round, to ½ inch in diameter, greenish-yellow flecked with whitish spots, inedible, with 2–4 black seeds. After freezes they soften, darken, wrinkle, and become palatable to birds.
Similar species: Several other trees bloom in spring with white, five-petaled flowers. Serviceberry has petals that are brighter white, strap-shaped, wavy, with a space between them (not rounded and close together). Native plums have stamens (threadlike stalks in the center of the flower) that are longer than the petals. Apple and crabapple flowers have a slightly pink hue, and apple tree branches are nearer to horizontal and less uniform, compared to the vertical, symmetrical branching of Callery pear.