Flowering crab apple trees are low-maintenance plants related to apple trees, with smaller edible fruits and different foliage and blooming time. They bloom early in spring and are one of the first plants to display color. Pruning takes special consideration, as crab apple trees are susceptible to certain diseases.
Time the pruning properly. In order to keep disease from the tree, you must prune in late winter or early spring, before the buds set. February to early April is the best time to prune. Pruning any later will increase the risk of the tree contracting fireblight.
Disinfect your pruning shears before using them. Wipe the blades down meticulously with a rag and rubbing alcohol. Clean the blades often as you work. This will prevent the spread of disease between your plants.
Cut rapidly-growing suckers coming from the base or roots of the tree. Also cut rapidly-growing watersprouts that grow straight up from the branches of the tree---they only take nutrients away from the main part of the tree. Cut right outside the root collar, the raised area where the stem meets the trunk.
Cut off dead, diseased, weak and broken branches. Also cut off crossing branches. This will open up the tree canopy, increasing air-flow, and help prevent diseases coming into the tree through weak branches. Remove other branches interfering with wires and buildings as you see fit. Be extra careful around wires.
Gather the pruned materials and throw them away. Leaving them on the ground will increase the amount of disease spores in the air.