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