Rhododendrons (Rhododendron spp.) are broadleaf evergreen shrubs that encompass about 1,000 different species, including azaleas. Rhododendrons originated from parts of Asia, Europe, North America and Japan, and most are fairly cold-hardy and can grow in a wide range of climates. Rhododendron shrubs bloom in early spring to early summer with large, showy clusters of white, pink or purple flowers. They have large, leathery leaves that persist throughout even the coldest winters. Rhododendrons are often used in landscapes as foundation plantings, individual specimens or even to create hedges and privacy screens.
Water your rhododendrons deeply to soak the soil down to and around the entire root zone once each week. Water the shrubs only when rainfall is less than 1 inch per week.
Feed your rhododendrons once each year after the shrubs finish flowering in spring with 2 to 5 lbs. of a balanced, slow-release fertilizer per 100 square feet. Select a fertilizer containing micronutrients such as magnesium and iron. Follow the application instructions on the label.
Spread a 3-inch-thick layer of mulch on the ground around the rhododendron to cover the entire root area to control weeds and retain soil moisture. You can use bark, straw, wood chips or other types of organic mulches.
Prune your rhododendrons immediately after the flowers fade in spring to remove all dead, diseased or damaged branches. Remove the faded blooms from the rhododendron and prune the selected branches back to the crotch at the trunk.
Prepare your rhododendrons for winter by adding more mulch in autumn to maintain a 3- to 4-inch-thick layer. Don't fertilize the rhododendrons after mid-July.