Rhododendron of the Month


Rhododendron arboreum

One of the most stately and impressive species rhododendrons, R. arboreum is extremely variable in stature, hardiness, flower color and leaf characteristics.

Originally discovered in North Central India by Captain Hardwick, the details of the first introduction of this magnificent rhododendron are somewhat uncertain but at least one authority believes the credit should be given to Dr. Francis Hamilton. At one time Dr. Hamilton was director of the Botanic Garden at Calcutta. He evidently was stationed on the border of Nepal in 1809 and 1810 from whence he sent seed to England.

Over the next 40 years (1810 - 1850) many plant explorers collected seed of R. arboreum from a fairly wide-spread area in the foothills of the Himalayas at altitudes ranging from 4,000 feet to over 11,000 feet. A rhododendron from 4,000 feet elevation in Sikkim will have far less chance of survival in the Pacific Northwest than will a rhododendron from 11,000 feet in Sikkim.

The flowers of Rhododendron arboreum range in color from a deep scarlet, to red with white markings, to pink to white. Bearing up to twenty blossoms in a single truss this rhododendron is a spectacular sight when in full bloom. It is reported that the bright red forms of this rhododendron are generally found at the lower elevations which explains why this form is severely damaged or killed to the ground during our coldest winters.

The foliage of Rhododendron arboreum is extremely handsome. Its thick, stiff, leathery dark green leaves are covered on the under surface with a thin layer of indumentum ranging in color from silver to fawn to deep cinnamon, elegant in foliage. From my limited experience I have noted that the reds usually have the light silver-colored indumentum while the leaves of the pinks and whites generally exhibit cinnamon indumentum.

In its native land huge trees of Rhododendron arboreum grow to a height of 60 feet or more, and in hospitable sites in cultivation 40 foot giants of this exquisite plant have been reported.

R. arboreum bud.
R. arboreum flower.
Images from the files of
The Rhododendron Species Foundation
An excerpt from
"Watts with the Species"
by Lynn Watts
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