A crabapple's main crop consists of flowers rather than fruit. Few crabapple varieties yield fruit of good quality, though the small bitter apples provide important winter forage for many wild animals and birds. Correct pruning should maintain the health of the tree without cutting back the density of the spring bloom. Trimming also protects the scion of grafted varieties from being overgrown by the rootstock of the tree.
Remove any root suckers by clipping them back to ground level with loppers. Root suckers could emerge many feet from the tree but divert nourishment from the parent plant if allowed to grow.
Cut out any vertical sucker shoots growing from the crabapple's branches. Vertical shoots compete with the tree's leader or central trunk and create a weak inner structure.
Trim out any lower branches shaded out by the upper canopy. Crowded growth limits air circulation within the branches and contributes to fungal disease. Shaded limbs die back naturally--removing them early improves the tree's health.
Find the graft junction and trim off any limbs or sucker shoots below it. Shoots from the rootstock grow with more vigor than the scion. Sucker shoots on even a mature grafted tree quickly dominate the tree's structure.
Look for crossed branches and remove the weakest of the pair. Cull any broken or damaged branches by cutting the damaged limb back to the first branch collar before the injury. Remove severely damaged branches entirely.
Thin crowded branch tips with pruning shears. Cut out any dead twigs first and then cut out enough small branches to allow growing room for new fruiting spurs. Thin branches only after the crabapple blooms to avoid reducing this year's flower crop.
Cut out larger branches with weak V-shaped saddles--the junction to the main trunk. Vertical saddles with inclusions of bark break easily in storms. Careful removal does less harm to the tree than accidental breakage. Selecting limbs with wide horizontal saddles yields a tree that needs less care.