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Species In Our Midst
Rhododendron tschonoskii

by Susan Clark

Rhododendron tschonoskii
Picture by S & J Perkins
Rhododendron tschonoskii in Concord, MA

Rhododendron tschonoskii

R. tschonoskii is in the subgenus Tsutsusi, section Tsutsusi, the evergreen azaleas. It is found in South Korea, Japan (Hokkaido, Honshu, Shikoku and Kyushu), Sakhalin and on the Kamchatka Peninsula of Russia. It grows on rocky mountain summits and ridges up to 4000', but is also found in moist woods and on shady rocks. Often it is on wind-swept heights in full sun. R. tschonoskii was first described by Maximowicz in 1870 and named for his Japanese collector, Tschonoski, who found it growing in the mountains in northern Japan. Veitch in England obtained seeds in 1878. Charles Sargent sent seeds from Japan to the Arnold Arboretum in 1892; E. H. Wilson also sent seeds but from Korea to the Arnold Arboretum in 1917. This species has been subdivided into two varieties, var. tschonoskii, with 4-5 prominent veins on the leaf undersides, and var. trinerve, with 3 veins on somewhat larger leaves.

R. tschonoskii is a small, multibranched shrub, often upright to 3' but sometimes spreading to form almost a mat. Its new growth is covered with dense adpressed reddish hairs. The leaves are small, mid-green above and pale below, and not quite an inch long, lanceolate to elliptic. Most Tsutsusi azaleas are dimorphic, having spring leaves, which are larger and deciduous, and summer leaves which are small and generally persistent (evergreen). R. tschonoskii ,unlike its Tsutsusi relatives, has monomorphic (only one kind). The leaves are entire (not divided or notched) and covered on both surfaces with whitish to pale brown adpressed hairs; the leaf petioles are also hairy with reddish-brown hairs. In fact most parts of this plant are 'strigose', covered with stiff hairs. One of this plants most desirable features is its fall coloring, when its leaves turn a bright orange-red or crimson. It retains few, if any, leaves into winter.

The flower of R. tschonoskii also distinguishes it from its near relatives. The white corolla is very small, 1/4 to 1/3 of an inch across and equally deep, with 4 or 5 separated lobes. It has 4 or 5 stamens, also unusual. It is a somewhat late bloomer, producing flowers after it is fully leafed out; the small flowers are rather hidden by the foliage. This leads the Coxes and Greer to consider it rather worthless in the garden, in spite of its hardiness and ease of growing.

Greer estimates R. tschonoskii as hardy to -15°F but so few of us are growing the plant in the Northeast that we have little hard data. Certainly two plants in Concord, MA are prospering; Dick Brooks and I have both had a plant grown from seed from the ARS 1992 seed exchange. I find it an agreeable little plant, a slow grower which looks very attractive nestled against an old stone wall. I have to remind myself to check for bloom (it really isn't very showy) but its compact uprightness pleases me.

Susan Clark, Concord, MA

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