Flowering Crabapples (Malus spp.) are common small ornamental trees in the Rose family. These should not be confused with the large-fruited eating apples grown in orchards. Some species are native to North America, but many have come from Europe and Asia. Flowering Crabapples are popular due to their colorful flower, leaf and fruit displays. Their fruits provide an important food source for birds and mammals, although fruits can be messy. There are hundreds of hybrids so exact identification can be difficult.
Many crabapples are riddled with pest issues (chewing caterpillars, rust, scab, and powdery mildew are common) and at some point in the growing season, many trees tend to look ratty and unhealthy. Caring for crabapples usually involves tending to their pest susceptibilities and smart applications of pesticides. Crabapples flower and fruit best if grown in full sun, otherwise too much shade or wet conditions aggravate disease. They have little need for pruning and it is usually done to remove cracked and dead branches or to manage disease. The ideal time of year to prune crabapples is late winter when diseases have slowed and plant defenses are strongest. Pruning should be kept minimal because heavy-handed pruning ALWAYS will respond with prolific sucker/shoot growth.
You will be most successful with a crabapple if you choose a disease-resistant variety, plant in a good location, stay on top of pest issues before they get out of control, and only prune lightly.