Daily Archives: November 8, 2010

Rhododendrons and Azaleas Classification & Differences

The Garden Artist Posted on by

This is part of an outline of a ten minute talk I gave to the Centerport Garden Club on November 9, 2010

HOW ARE RHODODENDRONS CLASSIFIED?

Rhododendrons are classified into two major groups, lepidote and elepidote?

  • Elepidotes are large leaved rhododendrons. They are the type of shrub that most individuals would associate as being a rhododendron. They do not have scales located on the underside of the leaves. Plants tend to be very large in their maturity.

    elipidote rhododendron

    Elipidote Rhododendrons have big leaves

  • Lepidote rhododendrons have smaller leaves and are usually low growing or dwarfs. They usually bloom earlier in the spring than the larger leaved elepidotes.

    lepidote rhododendron
    Lepidote Rhododendrons have small leaves

WHAT IS THE DIFFERENCE BETWEEN AZALEAS AND RHODODENDRONS?

rhododendron
Rhododendrons have 10 stamens, 2 per lobe

  • All azaleas are rhododendrons but not all rhododendrons are azaleas.
  • True rhododendrons have 10 or more stamens which is 2 per lobe. Azaleas usually have 5 stamens or 1 per lobe. Azaleas have 5 lobes in a flower
  • Azaleas tend to have appressed hairs which are hair parallel to the surface of the leaf. This is particularly true along the midrib on the underside of the leaf. It is easily seen in “evergreen” azaleas.
  • True rhododendrons instead of hair are often scaly or have small dots on the under side of the leaf.
  • Azalea leaves are never dotted with scales and are frequently pubescent.
  • Many azaleas are deciduous.
  • True rhodi’s are usually evergreen with the exceptions of R. mucronulatum and R. dauricum.
  • Azaleas have tubular funnel or funnel shaped flowers. Rhodi flowers tend to be bell-shaped.
    azalea
    Azaleas have 5 stamens, one per lobe

Rhododendrons and Azaleas- Classification

The Garden Artist Posted on by

This is an outline of a ten minute talk I gave to the Centerport Garden Club on November 9, 2010

Botanical Classification

Rhododendrons and azaleas belong to the genus Rhododendron of the heath family (Ericaceae).

  • The heath family includes the heaths and heathers, blueberries, mountain laurels and several other ornamental plant groups.  Most members of this family require acid soil and good drainage.

Rhododendron collectionThis is a selection of the Rhododendrons submitted to the judging of the Spring Flower Show at the NY Chapter of the American Rhododendron Society at Planting Fields Arboretum

Where are Rhododendron’s from?

Some are native to the US.

The British became the first explorers to seek out new additions.

Collecting has brought plants, seeds & cuttings from Japan, China & the Himalayas.

New species are still being collected in central China.

In the 1800’s they were so expensive & were considered a rich person’s plant. They appeared on estates and in arboretums.

Most of the Rhodi’s we know today are hybrids created from the parents of the plants collected by these plant explorers.

Azalea gardenAzaleas blooming in May in my garden in Northport NY

Common Types

  • Large leaf evergreen Rhodi’s: Great for screening and as a backdrop behind the flower garden, Catawbiense, English Roseum, Scintillation, Maximum
  • Small leaf evergreen Rhodi’s: some sport beautiful mahogany leaves during the winter months, Aglo, Dora Amateus, Mary Fleming, the PJM’s
  • Yakushimanum hybrids: usually 3’wx3’h with woolly indumentum on dark green leaves. Have wonderful winter interest, Crete, Fantastica, Ken Janek, Percy Wiseman, Prince & Princess
  • Species Rhododendrons, can present well in a mixed flower, shrub border. There is a species rhododendron garden in DC.
  • Azaleas-Evergreen: Michael Dirr begins his Azalea Cultivar & Hybrid Group section with:

“In some respects, it is paralyzingly frightening to attempt to present the cultivars of azaleas.”

There are so many but you can begin to study them realizing that some are named for their hybridizers: i.e. Girard Hybrids, Glen Dale Hybrids, Polly Hill’s North Tisbury Hybrids. Others by their location: i.e. Linwood Hybrids, Karume Hybrids of Japan.

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