Weigela (Weigela florida) grows in U.S. Department of Agriculture plant hardiness zones 4 to 9, producing deep green foliage throughout summer and featuring white, pink or purple flowers in spring. Although many varieties can reach up to 6 feet tall at maturity, it's possible to keep them pruned to a smaller size with annual trimming. Weigela shrubs go dormant in fall and don't resume growth until spring, so late winter is the best time for a severe pruning to control the size and spread of the plant.
Rinse a pair of bypass pruning shears and a small pruning saw in a solution of one part bleach and nine parts water before you begin trimming the weigela. The bleach disinfects the shears and prevents the spread of disease. Rinse the shears between cuts when you move between plants or prune out a dead or sick branch.
Examine the weigela for dead, damaged or crossed branches in late winter or early spring before growth resumes. Cut back the dead or damaged wood back to the nearest healthy wood. Trim out crossed branches so they don't rub together and cause damage. Use the pruning saw to cut out branches thicker than 1/2-inch, and use the shears for smaller branches.
Cut out up to one-third of the oldest, largest branches, removing them at their base where they join the trunk or a main branch. Removing old, overgrown branches maintains the size of the weigela so it doesn't grow overly large, and encourages vigorous new growth and more flowering.
Trim back overly long branches after you remove the oldest wood. Cut back these branches to a bud at the desired height, removing no more than one-third of the branch's length.
Shape the weigela lightly after it finishes flowering in late spring. Trim back the tips of the branches to shape the bush and maintain its size.