Complimentary 
NEVy SERIES VOL. Vll 
NO. 12 
ARNOLD ARBORETUM 
HARVARD UNIVERSITY 
BULLETIN 
OF 
POPULAR INFORMATION 
JAMAICA PLAIN, MASS. JUNE 30, 1921 
A few late-fiowering shrubs. As the summer advances the number 
of trees and shrubs in flower in the Arboretum rapidly diminishes and 
in the last week of June their number is not large. Some of the most 
interesting of them are 
Rhododendron maximum, with its pink and white flowers an inch 
long, in dense sixteen- to fourteen-flowered umbels four or five inches 
in diameter and overtopped by the fully grown branches of the year 
developed from buds in the axils of leaves just below the inflorescence 
bud. This growth of the branches before the opening of the flower- 
buds occurs in most late flowering Rhododendrons and hiding, in part 
at least, the flowers obscures their beauty. Rhododendron maximum, 
nevertheless, is a handsome and useful plant, with leaves larger and 
handsomer than those of any other Rhododendron which is hardy in 
this climate. Rare at the north where it grows in cold deep swamps 
in a few isolated stations in Nova Scotia, Ontario and New England, 
it is very abundant on the Appalachian Mountains from Pennsylvania to 
Georgia, making great impenetrable thickets along all the mountain 
streams and occasionally growing to a height of thirty or forty feet 
and forming a trunk a foot in diameter. When cultivated this Rhodo- 
dendron grows well in any soil which is not impregnated with lime; it 
will grow, too, in comparatively dense shade and when fully exposed 
to the sun. When exposed to the sun, however, it is often badly in- 
jured by the lacewing fly. Several hybrids between R. maximum and 
R. catawbiense hybrids have been raised. One of the earliest and the 
best known of these hybrids, R. delicatissimum, is a handsome plant 
with pink and white flowers which open two or three weeks before 
those of R. maximum and are not hidden by young branches. Rhodo- 
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