Both species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, and many species and cultivars are grown commercially. Most large commercial growers in the United States are located on the west coast.
Rhododendrons are valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen. Azaleas are frequently used around foundations and occasionally as hedges, and many larger-leafed rhododendrons lend themselves well to more informal plantings and woodland gardens, or as specimen plants. In some areas, larger rhododendrons can be pruned to encourage more tree-like form, with some such as R. arboreum and R. falconeri eventually growing to 10-15 m or more tall.
Like other ericaceous plants, most rhododendrons prefer acid soils with a pH of roughly 4.5-5.5; some tropical Vireyas and a few other rhododendron species grow as epiphytes and need a planting mix similar to that required for orchids. Rhododendrons have fibrous roots and prefer well-drained soils high in organic material. In areas with poorly-drained or alkaline soils, rhododendrons are often grown in raised beds using mediums such as composted pine bark. Mulching and careful watering are important, especially before the plant is established.
There are a number of insects that either target rhododendrons or will opportunistically attack them. Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will attack rhododendrons. Major diseases include Phytophthora root rot, stem and twig fungal dieback. [1]
All parts of Rhododendrons are toxic to animals if ingested. Symptoms include vomiting, diarrhea, hypersalivation, weakness, coma, hypotension, CNS depression, cardiovascular collapse and death. [2]
