Malus is the genus of about 30–35 species of small deciduous apple trees or shrubs. The other species and subspecies are generally known as "wild apples", "crab apples", "crabapples" or "crabs."
Apple trees are small, typically 4–12 m tall at maturity, with a dense, twiggy crown. 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; flowering occurs in the spring after 50–80 growing degree days (varying greatly according to subspecies and cultivar).
Additionally, crabapples, a genus of deciduous trees or shrubs that grow to be 6 to 50 feet tall, are among the most ornamental fruiting trees around with 2-inch, bitter fruits and broad, flat and lobed leaves. Crabapples come in weeping, columnar, spreading, vase-shaped and pyramid-shaped varieties. All of these forms can be found on the ISU campus.