Water apples bloom in early to mid-spring, producing masses of pink, red, or white flowers, depending on the variety. Some also have attractive purplish red leaves. Many types also produce small, red or yellow edible fruits that are tart but excellent for jelly. Most crab apples grow 15 to 25 feet tall and wide at maturity. Some weeping and dwarf forms grow less than 10 feet tall. Crab apples are susceptible to some of the same diseases as apples, including apple scab, so select resistant varieties. The fruit remains on the branches into fall, providing food for wildlife, and the branch structures on many varieties provide interesting forms in winter.
Select a site with full sun and well-drained soil.
Plant in spring or fall. Space plants 10 to 20 feet apart, depending on the expected mature size of the variety. Dig a hole only as deep as the rootball and two to three times as wide. If your soil is in very poor condition, amend the soil you've removed from the hole with a small amount of compost. Otherwise don't amend it at all. Carefully remove the tree from the container and set it in the hole. Fill the hole half full with soil, then water it well to settle the soil and eliminate air pockets. Let the water drain, then fill the remainder of hole with soil and water thoroughly.
Apply a layer of compost under the tree each spring, spreading it out to the dripline (the area under the outermost branches). Add a 2-inch layer of mulch to retain moisture and control weeds, keeping mulch a few inches away from the tree trunk. Water plants during the summer if rainfall is less than 1 inch per week. Crab apples require little pruning once established. In late winter, prune dead, diseased, and broken branches and trim off any sprouts that arise at the base of the tree.