alus is a genus of small deciduous trees in the family Rosaceae, including domesticated apples and crab apples. These species are widespread throughout the northern hemisphere in temperate zones. There are hundreds of cultivars of crab apples, many of which readily crossbreed. Typically, crab apple trees reach heights of 13–39 feet (4–12 meters) with dense, wide, rounded crowns. The leaves of apple trees are typically 1–4 inches (3–10 centimeters) in length, simple, serrated, and alternately arranged on the stem. The flowers have five petals and are typically white or vivid shades of pink or red. The fruits of the crab apple are called pomes or apples, varying greatly in size, color, and taste depending on the species of crab apple.
Crab apples prefer sunny sites but are otherwise very adaptable trees, tolerating many stressful conditions such as pollution, drought, and compaction. The fruits and flowers attract many insects and birds. The fruits of the crab apple are not commonly consumed due to their highly sour taste, but in some cultures, they are eaten. Due to their small size, vibrant spring blooms, and fruits that often remain attached throughout the winter, crab apples are extremely popular ornamentals. Hundreds of cultivars of crab apple are available, many of which have been awarded the Royal Horticultural Society’s Award of Garden Merit.