Horticulture Highlight: Azaleas, Rhododendron sp.

April 27, 2016

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…Come every spring to whisper near the tomb,

To stare, a little shaken, where the mosses mourn

And the azaleas and magnolias have not ceased to bloom…

                May Sarton

“Hardy azaleas are the gayest of shrubs. The flowers of no other group present such a range of brilliant colors-white, pink, yellow, orange, salmon to flaming red and scarlet in tones of great purity and vividness.  Many species are delightfully fragrant and all are abundantly floriferous.” So wrote Ernest Henry Wilson (1876-1930), notable horticulturist, author, plant explorer, as he opened his chapter on azaleas in his posthumously published (1931) If I Were to Make a Garden.

Spring Visitors jjj (31)Azaleas, Rhododendron sp. are one the most widely grown of our flowering shrubs. Native to North America, Europe and Asia, they are commonly known to be deciduous, but there are evergreen species as well. As a preliminary taxonomic understanding, today all azaleas are within the large genus Rhododendron, which worldwide comprises 900-1000 species, with at least 28,000 cultivated varieties. This genus was first formally described by Carl Linnaeus (1707-1778) in his Species Plantarum in 1753. At that time Linnaeus also described a separate genus for Azalea. In the 1830’s succeeding botanists reassigned all azaleas into an ever expanding rhododendron genus. In our modern era the use of molecular analysis has continued to bring revisions within this genus. Much of this is well beyond the scope of this discussion, but it allows us to quote Jane Brown, author of the engaging Tales of the Rose Tree: Ravishing Rhododendrons and their Travels Around the World, “Rhododendron taxonomy is a path to lonely sainthood…” Herein instead we present a sampling of spring flowering azaleas adding charm and grace within our May/early June landscape.

Rhododendron periclymenoides close upedit

Do you ever wonder about the Azaleas

They are special flowers of the spring…

                -John McCormack

Rhododendron schlippenbachii flower

Royal azalea, Rhododendron schlippenbachii is a deciduous shrub that might reach 6-12-feet in height. Native from Eastern China, Korea and Manchuria, it is named after Baron von Schlippenbach (1828-?), a Russian naval officer who discovered the species in the 1850’s along the eastern coast of Korea. The pink, 3 ½-inches in diameter, fragrant flowers open before the leaves emerge. The flowers’ five petals are rather flat, saucer-shaped, versus the more usual funnel-shape of many other azaleas. The pale-pink color elicits admiration from everyone. Expert plantsman Michael Dirr praises, “…one of the most delicate and beautiful of the azaleas for the northern gardens…no adequate way to do justice to the beauty of this plant by the written word…”Naturalist, photographer Albert Bussewitz (1912-1995) often referred to the tender elegance of these blossoms as being the color of the palest pink negligee. Look for a fine specimen on Narcissus Path along with another dozen of these growing elsewhere.

Rhododendron schlippenbachii close up

When spring comes, they stretch

their limbs, wakening, and slip

into a negligee, neglected, incomplete

attire of blossom and embryonic leaf…

                Kay Cheever

Pinkshell azalea, Rhododendron vaseyi is another deciduous springtime star when in flower. The 1 ½-inch diameter, pink to rose-colored, non-fragrant flowers have five, slightly flexed petals that are not totally fused together at their base. The five to seven stamens are often of different lengths. This 5-10-foot tall shrub is native to North Carolina’s Blue Ridge Mountains. It was first discovered in 1878 by George Vasey, then the botanist in charge of the United States National Herbarium, and was named in his honor by Harvard University’s renowned botanist Asa Gray (1810-1888), [Lot 3409, Holly Path]. Today this plant’s natural range is limited to just six counties and it is being monitored by North Carolina and national conservation botanists. Fortunately it remains widely available in nurseries. Autumn leaves turn a red-maroon color to provide a strong second season of ornamental interest. Look for Pinkshell azalea at Halcyon Avenue and Birch Gardens, among other locations.

Rhododendron vaseyi

So one day when the azalea bush was firing

away and the Japanese maple was roaring…

                Gerald Stern

Rhododendron kaempferi with Cornus florida

Torch azalea, Rhododendron kaempferi will be flowering slightly later than the Pinkshell azaleas, with a range of colors from salmon, orange-red, or rosy-scarlet. Flowering before its deciduous leaves, this is the most widespread Rhododendron in Japan, and has been popular in their gardens since the eighth century. The name honors the German explorer-physician, Engelbert Kaempferi (1651-1716), who lived for two years in Japan beginning in 1690, working with the Dutch East India Company. He created a small botanic garden there. Later in 1712, when home, he published descriptions and illustration of Japanese plants, including one of Rhododendron kaempferi. His other writings were posthumously translated into the English two-volume History of Japan in 1727, which helped fuel an acceleration of interest in Japan and Japanese plants throughout Europe.

The first Torch azaleas were not introduced into western gardens until 1892 when Charles Sprague Sargent (1841-1927), the first director of Harvard University’s Arnold Arboretum brought back seeds he collected in Japan. As the common name suggests, when in flower these will illuminate any landscape. Look for these on Pilgrim Path, Vesper Path and Oak Knoll Path among other locations.

Rhododendron kaempferi close up

 There is nothing like the Azalea

So welcome in the spring

Colors that warm your heart

Excitement they always bring…

-Marilyn Lott

Rhododendron calendulaceum habit

Flame azalea, Rhododendron calendulaceum is a deciduous shrub native to western Pennsylvania, Ohio, south to northern Georgia and Alabama. Flame azalea has the largest flowers and most variable colors of all the native azaleas. The 2- 2 ½-inch diameter, scentless flowers may be yellow, apricot, pinkish, orange or red. These have been favorite landscape choices for two-hundred years. William Bartram (1739-1823), American naturalist, plant collector and author spent four years, beginning in 1773, traveling throughout our southeast. In his famous Bartram’s Travels he referred to the flame azaleas as “…the most gay and brilliant flowering shrub yet known…” This would later be used as one parent of the Ghent hybrid azaleas. Look for these around Auburn Lake and Halcyon Lake.

Rhododendron calendulaceum flowers

with fragrance devine

and such magnificent regalia.

Oh, so fine,

Azalea…

    –Duke Ellington

…So go now to Azalea,

And listen to her tune,…

                -Steven Rodgers

~

About the Author: Jim Gorman

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