Rhododendrons are hardy shrubs that bloom in showy pink or purplish flowers in spring and bear deep green, leathery foliage year round. Rhododendrons are low-maintenance evergreen shrubs that require almost no care when they're planted in a native or otherwise appropriate climate. Old rhododendrons usually have fewer care demands than younger, newly planted ones, because they've already become well-established in their environment. Older rhododendrons usually have more pruning requirements, however, especially if they've been neglected for a number of years.
Water your rhododendron deeply and evenly once each week during the spring and summer, only in the absence of rainfall. Water the rhododendron in late fall or early winter one time if the fall season has been especially dry, but don't water the shrub during September or October to allow the rhododendron to harden off for the winter.
Spread a 2- to 4-inch-thick layer of heavy, coarse mulch, such as wood chips or bark, on the ground over the root area of the rhododendron shrub. Add more mulch each year in late fall to keep the layer to the desired thickness.
Feed your rhododendrons once each year in early spring with a slow-release fertilizer made for acid-loving plants. Apply no more than 2 pounds of fertilizer per 100 square feet and follow the instructions on the label.
Prune your old rhododendron shrub to remove all old, dead, damaged or crowded growth immediately after the shrub finishes blooming in late spring or early summer. Cut away all branches that are growing inward or touching the ground. Remove the flower stems as soon as the flowers fade.