Rhododendron semibarbatum • azalea

Rhododendron • Rhododendron / Azalea • シャクナゲ / ツツジ • 石楠花 / 躑躅 • shakunage / tsutsuji

Edited 5/31/14

I couldn’t find this azalea for several years, or missed its blooming time; it seats immediate south of the Oribe-gata lantern in the Roji  proper.

Kathleen Smith described it in the Plant List as ‘corolla cream with red dots’, and I thought it would be a striking, easy to find plant, but it took concerted efforts of the entire Planting Committee team to find it.  Kathleen’s Smith’s Notebook #5 shows it as planted in 1963 (tag # JG-305-59-A) in the JG, but not the main arboretum. It is a woodsy, 6-7′ tall  bush with small (1/2 – 3/4 inch) flowers shyly  ‘hanging below the expanded leaves’ (which matches ARS description of the plant).  The small flowers, blooming the end of May/beginning of June, have two shorter ‘semi-bearded’ stamens (hence the name) and grow in clusters, usually at the end of the branch.

SJG • 5/28/14 - Rhododendron semibarbatum, azalea, Area W, south of Oribe lantern in Roji - it's the V shaped bush in the center of the pic.

SJG • 5/28/14 – Rhododendron semibarbatum, azalea, Area W, south of Oribe lantern in Roji – it’s the V-shaped bush in the center of the pic.


SJG • 5/28/14 – Rhododendron semibarbatum, azalea, Area W, FLOWER – corolla cream with red dots. Pic by Maggie C.


SJG • 5/30/14 – Rhododendron semibarbatum, azalea, Area W, FLOWERS – in clusters, hanging below the leaves.

From Massachusetts chapter of American Rhododendron Society (click to see their flower): […] Native to the mountains of southern Japan, Rhododendron semibarbatum is usually listed as hardy to zone 7 although reportedly it varies in hardiness. This deciduous species is unique in having 5 unequal, dimorphic stamens where the 2 shorter stamens are densely pilose with globose-ovoid anthers. In fact its name ‘semibarbatum’ refers to these partially bearded stamens. The small (1/2 – 3/4 inch), white, rotate flowers are borne in clusters of 1-3 flowers in the axils after the leaves are fully expanded. Seed was collected by Wilson in 1914 and sent to the Arnold Arboretum and later on to Britain. It was first introduced by Tschonoski to the Botanical Gardens of St. Petersburg where it flowered in the greenhouse in 1870. An excellent botanical illustration of this species is found in The Book of Rhododendrons by Marianna Kneller. […]

No description, but good picture of ”Rhododendron semibarbatum” at Botanical Gardens, Tohoku University, Miyagi pref., Japan on Wikimedia Commons – small, down hanging flower, dots almost red.

No description, but 2 pictures at Hirsutum.

Link to pictures at Danish Chapter of ARS.

Link to Google Books – Journal of the Arnold Arboretum – will not let me copy –  scroll through description to read it.


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