Blueberries grow as thickets of branching canes rather than as single-stemmed fruiting bushes. Old canes stop producing good fruit crops after a few years. Bushes rejuvenate if cut short, but thinning mature canes annually causes a constant renewal process and steady fruit production. Blueberries also respond to thinning by producing higher-quality, larger berries.
Prune newly planted blueberry bushes back to about a foot in height. Remove side shoots, leaving only the strong vertical canes. Cutting back the tops of the plants puts less stress on the root system as the bush heals from transplanting damage.
Prune flower buds from blueberry bushes for the first three seasons to allow the plant to put its energy into growth. Bushes grow stronger and bear heavy crops sooner if not allowed to set fruit until they are mature. Only the last 3 inches of the year's new growth will bloom. Trimming that much from the ends of branches prevents the bush from flowering.
Cut out broken limbs and dead wood in late winter or early spring. Damaged branches should be snipped just short of the junction with a main branch or the blueberry cane. Thinning out blueberry branches reduces the overall bloom and causes mature blueberry bushes to produce better berries. Remove any crossed branches, and clip off any branches growing low enough to touch the ground. Open up the center of the plant to increase light and air circulation.
Trim out any diseased canes by cutting them off with limb loppers or a pruning saw just above ground level. Blueberries with a crowded growth habit sometimes become diseased; southern highbush blueberries may be especially vulnerable. Annually pruning the plants to an open growth pattern often prevents disease from taking hold.
Create a procession of young and older blueberry canes by cutting out any canes eight years old or more. Each year when new canes grow, select three or four of the strongest and cut back the rest to their base. When the new canes or suckers grow taller than the crown of the bush, cut them back to a few inches below the top of the older foliage. This forces the shoot to develop side branches which will bear fruit the next year.