Naming Genus



Azaleas are Rhododendrons
A Common Question

By Harold E. Greer

Rhododendron flammeum 'Hazel Hamilton'
Picture by S & J Perkins
Rhododendron flammeum 'Hazel Hamilton' in Salem, NH

What is the difference between a rhododendron and an azalea?

  • All azaleas are rhododendrons. They belong to the subgenus Pentanthera (deciduous) and the subgenus Tsutsusi (mostly evergreen) by the revised classification or to the Azalea Series by the Balfourian System.
  • All azaleas are elepidotes (they never have scales).
  • All azaleas have five lobes to the flower.
  • Most (not all) azaleas have only one stamen for each lobe of the flower, meaning they have five stamens while most other rhododendrons have two stamens for each lobe, meaning they have 10 or more stamens.
  • Azaleas tend to have adpressed hairs (hair that grows parallel to the surface of the leaf). This is particularly true along the midrib of the undersurface of the leaf and is easily seen in the so called "evergreen" azaleas.
  • Azaleas have tubular funnel or funnel shaped flowers.
  • You would need a microscope to see this, but while the hair on "standard" rhododendrons will often branch, the hair on azaleas never does.

[This article is from Greer's Guidebook to Available Rhododendrons Species & Hybrids which is an excellent reference for anyone interested in learning more about the genus Rhododendron.]

Notice the rhododendron pictured above has a flower consisting of five lobes and five stamens so it is commonly referred to as an azalea. Rhododendron canadense is an example of an azalea that has 10 stamens.

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