NEW SERIES VOL. I 
NO. 7 
ARNOLD ARBORETUM 
HARVARD UNIVERSITY 
BULLETIN 
POPULAR INFORMATION 
JAMAICA PLAIN, MASS. JUNE 8, 1915 
Rhododendrons. In the Bulletin issued April 28th attention was 
called to the damage which the Rhododendrons in the Arboretum had 
suffered during the winter, and it was suggested that it was caused 
by the severe drought of the autumn, followed by the unprecedented 
drought of March and early April, and not by cold which had not been 
exceptional. The Arboretum Rhododendrons certainly suffered from 
drought, but dryness alone will hardly account for such a destruction, 
for in other places near Boston plants in much drier and more exposed 
positions than those in the Arboretum are reported to have come 
through the winter uninjured. Some of the plants which were killed 
here have been twenty-five or thirty years in the country. These 
plants were grafted on Rhododendron ponticum, a plant which is not 
hardy here and is therefore not a suitable stock for Catawbiense hy- 
brid Rhododendrons to be grown in this climate. It is well known 
that these old grafted plants often lose large branches from what gar- 
deners call “canker,” and it is not impossible that the old plants 
killed in the Arboretum have been gradually failing for several years 
from the influence of the stock on which they had been grafted, and 
were therefore susceptible to extreme climatic conditions. This view 
is borne out by the fact that when plants of a particular kind were 
killed and others of the same kind were not killed it was always the 
oldest and largest plants of the variety that suffered. It has generally 
been supposed that it was the cross with R. arboreum and other Indian 
species which has made so many of the varieties of R. catawbiense ten- 
der in this climate, but some of the varieties which show in their bright 
red flowers this influence, like Atrosanguineum, Charles Dickens, and H. 
W. Sargent are uninjured, while many of the pale-flowered kinds like 
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