Rhododendrons, distant relatives of blueberries and heathers, are perennial members of the Ericaceae family that originated in Asia, India and Europe. More than 1,000 rhododendron species populate the world. The colorful, exotic blooms and foliage of these popular shrubs work well in mass plantings and in combination with other shrubs to create landscape interest. Different species within the rhododendron genus are suitable for different climates throughout the world. Rhododendrons require partial shade, consistent moisture and nutrient-dense soil with excellent drainage and a pH of 5.5.
Prepare your growing medium by combining equal amounts of peat or organic compost, sawdust and sand.
Cut a 1- to 4-inch piece from the tip of healthy, soft wood on existing rhododendron plants one to six months after new growth appears. The softer the wood, the easier the cutting will take root.
Remove all lower leaves on the cutting and score the base of the stem, especially on harder wood cuttings, to expose the inner flesh of the stem.
Dip the cut end of the stem into rooting hormone, following the rooting hormone manufacturer's directions. Fraser South Rhododendron Society recommends using a rooting compound that contains indolebutyric acid for successful rooting.
Insert the cut end of the stem into the growing medium deep enough to keep it in an upright position.
Mist the soil and cutting with water, then cover with a clear, plastic bag. Keep the soil moist, but never saturated, during root development.
Place cuttings in a warm location, at least 70 degrees Fahrenheit, out of direct sunlight.
Collect seed pods from existing rhododendron cultivars in the fall. The Portland chapter of the American Rhododendron Society recommends waiting four to six months after fertilization to collect seeds.
Store seed capsules at room temperature for up to two weeks to allow the seeds to dry properly. Place the seed capsules in a pan or tray, as the capsules may open during the drying process, releasing very tiny seeds.
Spread a layer of lightly moistened seed-starting potting mix in a tray or seed flat.
Sprinkle seeds evenly over the surface of the potting mix. Since the seeds are very tiny, it is not necessary to cover them with soil after broadcasting.
Cover the seed tray with plastic and place it in a dark location that maintains a constant temperature of 65 to 75 degrees Fahrenheit.
Transplant established seedlings to individual containers when they develop one to two sets of true leaves.
Make a 3- to 4-inch-deep trench beside an existing rhododendron plant.
Choose a healthy, established limb from the bottom of the plant closest to the prepared trench and score the bottom of the branch at the center point. The American Rhododendron Society recommends cutting less than halfway through the branch to create a "tongue," with the tip of the cut facing the parent plant.
Bend the branch into the trench, secure it with a hook stake and cover it with soil. If no stake is available, bend the branch into the trench, cover it with soil and place a large rock or brick on top to weigh it down.
Check the layered branch throughout the growing season for proper moisture and root development. If development is slow, rooting hormone can be added to the scored portion of the branch.