—e 
A. Tate Ie) 
Gr ASD Phy NeviAW GWAC ZT NE 
291 
The deciduous Rhododendrons (Azaleas) are among the most gorgeous of the Spring 
A mixed lot shown here 
flowering shrubs. 
tails beginning again. It means beginning here 
in New England and elsewhere in this country, 
and breeding a race suited to the climatic con- 
ditions which obtain; it means abandoning the 
old and lazy policy of relying upon other lands 
to supply our needs in this respect; it means 
that we must do here what Europe has done, 
namely, work out our own salvation. We start 
later than they across the Atlantic but we 
start with great advantages including those 
which have accrued from the labors of the 
past. A little of that concentrated effort and 
skill which has produced that most typical of 
American floral products—the Perpetual Flow- 
ering Carnation—would yield us our desire in 
the matter of a race of hardy broad-leaved 
evergreen Rhododendrons. 
The present day race of evergreen Rhododen- 
drons is essentially an English product and to 
better understand the subject let us briefly 
investigate its early history. No Rhododen- 
dron is native of the British Isles and the first 
of the evergreen section to be introduced was 
R. maximum, indigenous to eastern North 
America, which flowered for the first time in 
London in 1756. <A few years later (1763) R. 
ponticum was introduced and was followed in 
1803, by Rk. caucasicum. The American R. 
catawbiense was introduced by John Fraser 
about 1809, and was common in gardens in 
1838. Here are the beginnings of the Rhododen- 
dron cult in England. Of these four species 
two only (i. ponticuwm and R. catawbiense) 
have played a major part. 
As a breeder R. ponticum has been the great- 
est asset and although its color is not good it 
has proved extraordinarily adaptable in Great 
Britain and Ireland. This species grows wild 
in southern Spain and reappears in Asia 
Minor, in Syria and the warmer parts of the 
Caucasus. These regions enjoy a much warmer 
climate than does New England and from our 
viewpoint it is a tender species and unsuitable 
as a breeder. Also, for the same reason, it 
ought not to be used as a stock for grafting, 
yet, unfortunately, it is the stock so employed. 
An appreciation of these facts explains in a 
large measure the doubtful hardiness and un- 
certainty of the present-day race of Rhododen- 
drons since the blood of this tender species 
enters largely into the majority of the varieties. 
In the matter of hardiness the American R. 
catawbiense has been the greatest of all gifts 
in the realm of Rhododendron and the hardi- 
ness of our present-day race depends almost 
solely upon the dominant influence of the blood 
of this species. 
Rhododendron caucasicum is native of the 
higher Caucasus peaks and should be of much 
value to us since it is quite hardy in New 
England. Unfortunately it has been very little 
used by hybridists but such offspring as Boule 
de Niége, Coriaceum, Jacksonii and Mont Blane 
are very satisfactory plants in the Arnold 
Arboretum. 
_Our native R. maximum though the first spe- 
cies introduced to cultivation has played a very 
unimportant part in the evolution of present- 
day Rhododendrons. In a manner it has been 
disappointing yet it is questionable if it has 
had a fair chance. To us its hardiness and 
late flowering are qualities of vast import. 
The first authentic hybrid is considered to 
have arisen accidentally about 1820, between 
R. ponticum and R. nudiflorum (an American 
species of the Azalea section) and is still in 
cultivation under the names of R. odoratum 
and Rk. azaleoides. About the same time P. 
catawbiense was crossed with Rk. ponticum but 
the results were unimportant. Other early 
hybrids were Hybrid Maximum (Rf. ponticum 
x R. maximum) and Caucasicum album (R. 
ponticum album x R. cawcasicum) . 
The earliest introduced species were lacking 
in color and their hybrid offspring had the 
same defect. In 1811, the Himalayan R. ar- 
borewm with intense red flowers was introduced 
to England and this marked an epoch in the 
eult of the Rhododendron. The first really im- 
portant hybrid resulted from crossing Kk. ar- 
Rhododendron arbutifolium, low shrub of open, 
spreading habit useful for either shaded or sunny 
banks. Flowers rose color 
boreum and R. catawbiense in 1826, and was 
named R. altaclarense and the present-day race 
may be said to date from this period. But this 
magnificent Himalayan species is less hardy 
than R. ponticum and is quite unsuited to the 
climate of New England. Furthermore it 
flowers very early which is another drawback. 
Up to about 1850, these were the only species 
of this section of Rhododendron in cultivation 
and such hybrids as were raised resulted from 
their interbreeding and that of their offspring. 
In 1848, R. Griffithianwm was introduced to 
England from the Sikkim Himalaya and in 
1855, R. Fortunei from eastern China. These 
two species have given birth to many wonderful 
hybrids, but, alas, all of them too tender for 
this climate. Other Himalayan species have 
played a part in the evolution of the wonderful 
variety of Rhododendrons eminently suited to 
the moist and mild climate of the British Isles 
but their influence has not made for a race of 
value to eastern North America. 
A fairly hardy evergreen hybrid Rhododendron, Cunningham’s White. 
is typical of the possibilities of these plants 
This effect 
In a general way it may be said that Rhodo- 
dendron breeders in England until late in the 
nineteenth century kept away from the species 
as much as possible and intermingled the blood 
of the best of the hybrids. Some like the 
famous house of Waterer never lost sight of 
the invaluable quality of hardiness possessed 
by &. catawbiense and it is these men that we 
must thank for such blessings as we possess 
among the present-day race. “Lethe the 
species have been more favored for breeding in 
Kngland, and in Cornwall since the advent of 
a host of new ones from China Rhododendrons 
may be seen in bloom in every month of the 
year. 
Such are the bald outlines of the Rhododen- 
dron cult in England and for our purpose there 
is no necessity to go more deeply into the mat- 
ter. It lays before us the origin of the present- 
day race and points clearly to the cause of its 
lack of hardiness in the severe climate of New 
England. 
THE WAY OUT 
ET us now take stock of the field in general. 
The regions where Rhododendrons hardy in 
Great Britain grow naturally have been fairly 
well explored. Not all the species have been 
brought into cultivation, but to-day we are in 
a position to take a comprehensive view of the 
whole situation; and, insofar as the colder 
parts of this country are concerned, certain 
acts may be deduced. And it is on these bed- 
rock facts that we must rely and build if we 
are to obtain the object desired. 
Rhododendrons are found wild in the moist 
temperate parts of the northern hemisphere 
and a certain group extends through the tropics 
of Malaysia to northern Australia but for the 
purpose of this article this group may be elim- 
inated for reasons which are obvious. Ever- 
green Rhododendrons are essentially mountain 
plants and a majority grow naturally in woods 
and not a few are purely alpine. No species 
has been found in Africa, nor in South America. 
Of the large-leaved section only four species 
(R. ponticum, R. caucasicum, R. Smirnoww and 
k. Ungeri) are found in Europe and Asia 
Minor including the Caucasus. In North 
America only three species (Rk. maximum, KR. 
catawbiense and R. californicum) occur. Japan 
has but three (R&R. Metternichii, Rh. brachycar- 
pum and Rk. chrysanthum). The great concen- 
tration is in western China and the Himalaya 
where more than one hundred species have been 
discovered. It had been expected that the 
floral wealth of central and western China 
would have added a few species to the list of 
large-leaved Rhododendrons hardy in New 
England even though the Himalayan region 
had failed us, but, unfortunately, these hopes 
have not been realized. Admitting that Ane 
is disappointing nothing is gained by dwelling 
upon it despondently and some of these Chinese 
species will yet stand us in good stead. 
Of the introduced species of Rhododendron 
with large evergreen leaves five only are hardy 
in the Arnold Arboretum. These are the native 
R. maximum and FR. cataiwbiense, R. Smirnowi 
and R. caucasicum from the Caucasus and R. 
brachycarpum from northern Japan and north- 
ern Korea. One other species (R. chrysan- 
thum) with pale yellow flowers ought to be 
hardy here for it grows in the cold regions of 
