The leaves are 3–10 cm long, alternate, simple, with a serrated margin. The flowers are borne in corymbs, and have five petals, which may be white, pink or red, and are perfect, with usually red stamens that produce copious pollen, and an inferior ovary. The fruit is a globose pome. The centre of the fruit contains five carpels arranged star-like, each containing one to two (rarely three) seeds.
flowering occurs in the spring after 50–80 growing degree days. Apples require cross-pollination between individuals by insects. All are self-sterile, and self-pollination is impossible, making pollinating insects essential. The honeybee and mason bee are the most effective.
Crabapples are an excellent source of pectin, and their juice can be made into a ruby-coloured jelly with a full, spicy flavour. A small percentage of crabapples in cider makes a more interesting flavour.
They are also used as pollinizers in apple orchards. Varieties of crabapple are selected to bloom contemporaneously with the apple variety in an orchard planting, and the crabs are planted every sixth or seventh tree, or limbs of a crab tree are grafted onto some of the apple trees. In emergencies, a bucket or drum bouquet of crabapple flowering branches are placed near the beehives as orchard pollenizers.
Apple wood "makes a wonderfully luxurious firewood with a lovely scent, and smoke from an apple wood fire gives a most excellent flavour to smoked foods," including Applewood cheese.