There are more than 800 species and thousands of cultivars and hybrids of rhododendron, giving gardeners a variety of evergreen and deciduous shrubs to choose from. Depending on the species, the plant does well in zones 4 through 8, with some varieties specifically suited for mild climates such as the Pacific Northwest and the Southeast United States.
Pruning Deciduous Rhododendrons
Prune deciduous rhododendrons in the summer after the shrub has flowered, suggests the American Rhododendron Society. Pruning is necessary to encourage young growth from the ground up; many shrubs of this type become twiggy and top heavy when not pruned on a regular schedule. Cut back flowered shoots, remove dead, weak and spindly stems and cut any crossing stems to form a well-balanced and open-centered shrub.
Pruning Evergreen Rhododendrons
Evergreen rhododendrons tolerate severe pruning, according to The American Horticultural Society in the "Encyclopedia of Gardening." Evergreen rhododendrons need very little pruning once they have been established. To build a well-balanced framework, remove any weak or crossing shoots or any branches that upset the symmetry of the shrub in mid-spring, just before new growth begins. Remove any straggling growth to shape the plant.
Deadheading and Pinching
Deadhead rhododendrons by cutting off any spent and fading flowers from the branches to encourage more budding during the next flowering season. Deadheading also prevents fungus from forming and excess seed from accumulating, according to the "Complete Guide to Gardening" by Better Homes and Gardens.
Gardeners also pinch rhododendrons by removing the growing tip with a single pinch just above a leaf or pair of leaves, which causes the shrub to produce more flowers. Pinching can also channel extra energy into making leaves.