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Rhododendron Basics & Gardens
Hybrid Rhododendron 'Catherine Josephine' (Howard Kline) †
 Rhododendrons are shrubs of the genus Rhododendron, which is in the heath family (family Ericaceae). The heath family includes heathers, Kalmia (mountain laurels), blueberries and cranberries as well as rhododendrons. Since almost all of these plants require acidic soil, they are often referred to as the family of acid-loving plants. Rhododendrons are found in the wild, chiefly in mountainous areas of the arctic and north temperate zones. They typically have large, shiny, leathery evergreen leaves and clusters of large pink, white, or purplish flowers. North American species include the great laurel, or rose bay (R. maximum), West Virginia's state flower; and the Western rhododendron (R. macrophyllum), Washington's state flower. Azaleas are in the same genus, thus they are rhododendrons. North American native deciduous azalea species are prized for their bright colors.
Most cultivated rhododendrons are hybrids or cultivars that are propagated from cuttings or tissue culture. Rhododendrons are referred to as the King of Shrubs since they are regarded by many as the best flowering evergreen plants for the temperate landscape. Rhododendrons are shrubs for all seasons. In winter some stand out with large evergreen leaves. In spring the flowers are showy. Throughout the summer and fall the leaves add a pleasing, deep green color to the garden. Some deciduous azaleas add bright fall color before the leaves drop. The spectacular spring flowers of azaleas and rhododendrons make them among the most popular garden shrubs.
Rhododendrons are divided into 5 groups:
- Elepidote Rhododendrons: Rhododendrons without scales, typically the larger leaved rhododendrons.
- Lepidote Rhododendrons: Rhododendrons with scales, typically the smaller leaved rhododendrons.
- Deciduous Azaleas: Azaleas that typically put out new leaves each spring and drop them in the fall.
- Evergreen Azaleas: Azaleas that put out spring leaves and then summer leaves. Neither set lasts a full season.
- Vireya Rhododendrons: Lepidote rhododendrons that are tropical and will not withstand a freeze.
When botanists categorize rhododendrons and azaleas they refer to scales. These "scales" are about three-time the diameter of a human hair and are easily visible with a hand lens. The term lepidote is used to describe the rhododendrons with scales on their leaves and stems, while the term elepidote is used to describe the rhododendrons without scales. All azaleas are also elepidotes. About one third of all rhododendron species are in a group of tropical rhododendrons called Vireyas. Vireyas are classified with the other lepidotes in the subgenus Rhododendron.
The following articles were printed in the Journal of The American Rhododendron Society or in the ARS Rhododendron & Azalea News:
About Rhododendrons
Selecting Rhododendrons
Growing Rhododendrons
Rhododendron Gardens in America's Garden City
The following are articles printed about gardens in the Philadelphia area, America's Garden City, in the Journal of the American Rhododendron Society:
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