The Pruning Time for Rhododendron

Regular Maintenance

• Trim away any dead, broken or diseased branches from the rhododendron shrub at any time, regardless of season. Errant branches that compromise safety or pose a hazard may also be pruned as necessary. Branches that rub against a house facade, encroach on a more valuable nearby plant or jet out and block passage or view from a sidewalk or driveway all need trimming as soon as feasible. To improve the appearance of a rhododendron shrub once the flowers drop, the old trusses may be clipped off so no seed capsules form.

Pruning Time Frame

• To shape the rhododendron or limit the amount of new growth, time pruning for late spring, or immediately after the flowering display ends. This time frame allows you to enjoy the annual flowering and then shape the shrub with ample growing time for buds to sprout and mature before the onset of frosts in autumn. Pruning to create a more pleasant, balanced silhouette may also be done in early spring after the threat of frost passes. Pruning this early does, however, remove the flower buds that will soon open.

Rejuvenation

• After 20 to 30 years of growth in the garden, some rhododendron shrubs may lose a tight, rounded shape. The older plant may be leggy or lean in an awkward manner, exposing bare branches, and produce few flowers and new leaves. It may be time for a rejuvenation pruning in early spring. Cut back all branches to a height of 12 to 24 inches tall, staggering heights among multiple branch stumps. New buds sprout on the stumps to create a denser plant. The early spring pruning sacrifices any flowering for that year, but the subsequent regrowth and maturation of new branches rewards you in two years with a fantastic flowering.

Tools

• Use a sharp-bladed hand pruners to cut any twigs or branches less than 3/4 inch in diameter. On larger branches from 3/4 to 1 1/2 inches thick, loppers -- also called lopping shears -- are better. When cutting into the lower reaches of branches, such as when conducting a rejuvenation of the shrub, a pruning saw works best. Grasp onto the upper part of the branch to stabilize it as you cut into the thick, woody branch base. Clean, uniform cuts are much better than having tearing bark wounds from a poorly executed cut from a tipping and snapping rhododendron branch.