Complimentary 
NEW SERIES VOL. VII 
NO. 7 
ARNOLD ARBORETUM 
HARVARD UNIVERSITY 
BULLETIN 
OF 
POPULAR INFORMATION 
JAMAICA PLAIN, MASS. MAY 27. 1921 
Rhododendrons with evergreen leaves are widely scattered over tem- 
perate regions of the northern hemisphere and extend into the tropics 
in southern and southeastern Asia. Several hundred species are now 
recognized, the largest number on the eastern Himalayas and on the 
mountains of southwestern and western China where botanical explor- 
ers have recently found innumerable new and often handsome species. 
One or two species grow in northern China, two in central Japan, one 
in the Pacific states, and five in the Atlantic states of North America; 
two species grow on the mountains of central Europe and four in the 
Caucasus. The number of species which can be successfully grown in 
the Arboretum is only nine; four from eastern North America, one 
from Japan, one from China, one from the Caucasus and two from 
Europe. Of these several are rare in American gardens, in which 
hybrids are generally cultivated. Eastern North America is not a 
Rhododendron country. A few of them grow better on Long Island 
than they do in New England; they might grow more successfully in 
Pennsylvania and Delaware where they have not been very largely 
planted, or in some favored valley of the Piedmont region of Virginia 
or North Carolina; further south the summer sun is too hot for many 
of the species. On the northwest coast of this continent in western 
Oregon, Washington and southern British Columbia the soil, moisture 
and temperate climate are favorable to broad-leaved Evergreens, and it is 
in that region that it seems possible to establish a collection of Rhodo- 
dendrons which might equal and perhaps surpass the great collections 
of southwestern England, in the best of which several hundred species 
now fiower every year. In the United States Rhododendrons have 
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