JUNE, 1916 
et (Gra ep ie Ng elt AnG AZ) NH 
289 
scends more than a foot below the sur- 
face. Obviously a mass of fine hair-like 
roots near the surface of the ground 
cannot withstand drought and the need 
of a mulch of leaves is clearly shown. 
On account of their fibrous root system, 
Rhododendrons are easy subjects to 
transplant provided this be done with a 
large ball of earth and due attention be 
given to keeping them properly supplied 
with water afterward. 
The hardy members of the Azalea sec- 
tion are all virtually deciduous and a 
majority will stand more exposure to 
sun and drier conditions than will their 
evergreen relatives, but drought has 
very evil effects upon these also. It is 
advisable to place these Azaleas fairly 
close together and, as a ground cover, 
to plant different varieties of Heather 
(Calluna vulgaris) and hardy Heaths 
(Erica carnea, H. vagans), which are 
not only pretty in themselves but mask 
the ground from the sun’s rays. An- 
other and highly important item in the 
culture of all Rhododendrons is to re- 
move all flowers after they have faded 
to prevent the development of seed pods 
and te encourage new growths. 
A race of Rhododendrons that will 
thrive in limestone scils is at present a 
desideratum. There are several Chinese 
species which grow naturally on such 
soils, and it is within the bounds of 
probability that the future may see a 
race at least indifferent to this mineral. 
At present, however, those whose gar- 
dens are in limestone areas must give 
up thoughts of growing these plants 
unless they are prepared to make elab- 
orate preparations and take the risks 
involved. To those desirous of such ex- 
periments it may be pointed out that 
mounds of prepared soil should be made 
and not dug out beds filled with suitable 
compost since the lime has a very much 
smaller chance of impregnating a raised 
site. 
For the purpose of this article hardy Rhodo- 
dendrons may be divided into two groups 
known popularly as Azalea and Rhododendron. 
In the first the leaves are deciduous or nearly 
so ard rather small; in the second the leaves 
are persistent and 
usually of good size. 
These main groups 
are pretty clearly 
denned in the minds 
of all garden lovers, 
but it is convenient 
to subdivide them 
again: the Azaleas 
into three smaller 
classes and the Rho- 
dodendrons into two. 
The three sections 
of Azalea may be 
briefly characterized 
as follows: 
I. RooporA: Flow- 
ers from a ter- 
minal bud, 
leafy shoots 
from separate, 
axillary buds; 
corolla almost 
two-lobed; sta- 
mens seven to 
ten. 
Il. PENTANTHERA: 
Corolla funnel- 
form, stamens 
five, otherwise 
as in Rhodora. 
Rhododendron flavidum, 
flowers pale yellow. A new 
dwarf Chinese plant useful 
for rock gardens 
flowers of any other plant. 
III. Tsursutsr1: Flowers and shoots developed 
from the same terminal bud. 
(1) The first section includes the Rhodora 
(RK. canadense) and R. Vaseyi, both good garden 
plants which thrive best in rather moist soil 
in the neighborhood of water. The Rhodora 
grows wild from Newfoundland to Pennsyl- 
vania and New Jersey, and in the north in May 
covers large areas of swampy land with a sheet 
of bloom. This dwarf shrub, with ity small 
rose-purple flowers, is so well-known that fur- 
ther details are unnecessary. Early in May 
R. Vaseyi opens its compact clusters of small 
pink flowers before its leaves appear. This 
Azalea is an inhabitant of a few of the high 
valleys of the Blue Ridge Mountains in South 
Carolina and had been entirely overlooked until 
some thirty years ago. It is a shrub with slen- 
der stems, and of loose irregular habit, some- 
times growing to the height of fifteen or eigh- 
teen feet, although under cultivation it begins 
Rhododendron intricatum, flowers pale violet, a new 
type from China that is valuable for the rockery 
to blossom when less than a foot high. It is 
perfectly hardy and the pure, perfect pink of 
its flowers is scarcely equalled by that of the 
There is also a 
with white 
form (album) of this Azalea 
flowers. 
(IL) Eastern North America is very poor in 
species of evergreen Rhododendrons but it can 
claim to be the richest region in the world for 
the section Pentanthera. Of the thirteen species 
belonging to this group eight are native of the 
Atlantic seaboard, and one (IR. occidentale) of 
the western slopes of the Cascade and Sierra 
Nevada Mountains of the West, and another 
(R. sonomense) with smaller, rose-colored fra- 
grant flowers, grows on dry slopes of the moun- 
fains near San Francisco, but is not in cul- 
tivation. Of the other three, one (R. japoni- 
cum) is confined to Japan and Korea, another 
(R. sinense) to eastern and central China and 
the third (R. luwtewm) to the Caucasus, the re- 
gion in Asia Minor bordering the Black Sea 
Known in ancient times as Pontus, and to 
Galicia where only recently it has been discov- 
ered. Of the American species of this group 
five are well established in the Arnoll Arbo- 
retum and no group of plants perfectly suited 
to our climate surpasses them in beauty. The 
first to open their flowers are I. canescens and 
R. nudiflorum. Both have fragrant pale rose 
or pink flowers of various shades which appear 
before the leaves or just as they begin to un- 
fold. In general appearance these two plants 
are very similar but one is a southern and the 
other a northern plant though there are places 
where they grow together. The plants are 
twiggy, of medium size, and grow singly or in 
great masses on treeless hillsides or in open 
woods. Rhododendron canescens is very abun- 
dant in parts of Worcester County, Mass., 
and R. nudiflorum is especially common in the 
Gulf States from eastern Florida to eastern 
Texas. 
The next to blossom is R. calendulaceuwm, the 
yellow Azalea of the Appalachian Mountain 
slopes which opens its flowers early in June. 
The color varies from bright yellow to orange 
or shades of red and the beauty is heightened 
by contrast with the dark green leaves which 
are well grown before the flowers op . It is 
a rather slow growing but long lived plant, 
from eight to ten feet tall, and the beauty of 
its brilliant colored flowers is not surpassed by 
those of any other Azalea. The Yellow Azalea 
is followed by &. arborescens another inhabi- 
tant of the glades of the Appalachian Moun- 
tains from Pennsylvania to Georgia which 
blooms about mid-June. This is a tall shrub, 
growing from ten to fifteen feet high, with 
large, pure white, very fragrant flowers, the 
beauty of which is increased by the bright scar- 
let color of the long exserted stamen-filaments 
and styles. The leaves are pale colored and are 
full grown before the flowers open. The last to 
flower is R. viscosum, the Clammy Azalea or 
Swamp Honeysuckle, a common inhabitant of 
swamps near the Atlantic seaboard, which 
does not open its flowers until July. It is a 
shrub of medium size with small, very fragrant, 
pure white blossoms covered with sticky hairs 
and the leaves are often pale bluish especially 
on the lower surface. dhe plant is valuable 
for the lateness of its flowers, which continue 
to open for weeks when those of most shrubs 
are past. 
These five Azaleas are all good garden plants 
which take kindly to cultivation and thrive in 
ordinary soil in either open or shady situations. 
Of the other American species of this sec- 
tion seedlings of R. austrimum and R. can- 
didum are growing in the Arnold Arboretum 
but it is too early to judge of their merits as 
garden plants. The first has pale yellow flow- 
ers appearing before the leaves and is native of 
the valley of the Apalachicola River in western 
Florida; the second has white or pale pink 
flowers which appear after the leaves and is 
native of southern Georgia. Another species 
(R. flammeum) common in open woods in parts 
of central Georgia, is not in cultivation. The 
Western R. occidentale with its lovely white 
flowers has not yet been successfully acclima- 
tized in the Arnold Arboretum. 
The Chinese R. sinense has large, rich yellow 
flowers and is almost hardy with us; the other 
east Asiatic species (R. japonicum) is per- 
fectly hardy and its large flame colored flowers 
are very handsome. These species grow from 
four to six feet high and have stiff and rela- 
tively thick ascending branches. The remain- 
ing species (R. 
luteum, or incor- 
rectly R. flavum), 
commonly known as 
Azalea pontica, is 
not hardy in the 
Arnold Arboretum. 
It has been much 
used in hybridizing 
as we shall presently 
see but it is doubt- 
ful if the true spe- 
cies is in cultivation 
in this country. 
As shown above 
there is a _ great 
range of color in the 
American Azaleas 
and being perfectly 
hardy one would 
naturally expect to 
find them very gen- 
erally planted in the 
gardens of eastern 
North America. 
Such, however, is not 
the case for the sim- 
le reason that it is 
A ficult to procure 
them for very few 
American. nursery- 
men are willing to 
devote the time and 
trouble nece sary to 
Rhododendron 
sum, flowers pure pink to 
pale rose, suitable for rock- 
eries and for massing 
Tracemo- 
