Rhododendrons, vigorous perennial shrubs, are grown for their showy flower clusters and greenery. Trim your rhododendron by cutting off fading flowers, or by pruning a mature shrub down to leafless sticks.
According to the American Rhododendron Society, removing spent foliage and flowers encourages new growth. You can also prune back to older wood; new, branching growth will fill out the shrub.
Nip back young rhododendrons by pruning stems back to a leaf rosette. Auxiliary buds fill out with new leafy growth. Snip off spent blooms, called deadheading, to clean up shrubs after flowering.
Renew your rhododendron in thirds. After flowering, cut out one-third of the shrub stems down until they are only several inches tall. Do this for three years for full renewal.
Prune your older rhododendron down to the leafless stalks or stems after flowering. This drastic pruning revitalises the whole plant. The National Rhododendron Society recommends drastic pruning only for shrubs with multiple stems. Hybrids with only one stem may not survive.