Ernest Henry Wilson.

A monograph of azaleas : Rhododendron subgenus Anthodendron online

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BERKELEY
LIBRARY

JNIVERSITY OF
CALJPORMIA

LANDSCAPE
ARCHITECT'',;*



The Gift of Beatrix Farrand

to the General Library
University of California, Berkeley



REEF POINT GARDENS
LIBRARY




PUBLICATIONS OF THE ARNOLD ARBORETUM, No. 9



A

MONOGRAPH OF AZALEAS

RHODODENDRON SUBGENUS
ANTHODENDRON



BY

ERNEST HENRY WILSON

AND

ALFRED REHDER




ISSUED APRIL 15, 1921



PRINTED FROM THE INCOME OF THE WILLIAM L. BRADLEY FUND



THE UNIVERSITY PRESS

CAMBRIDGE
1921









A MONOGRAPH OF AZALEAS






.
.






PUBLICATIONS OF THE ARNOLD ARBORETUM, No. 9

A

MONOGRAPH OF AZALEAS

RHODODENDRON SUBGENUS
ANTHODENDRON

BY

ERNEST HENRY WILSON

AND
ALFRED REHDER







ISSUED APEIL15, 1921



PRINTED FROM THE INCOME OF THE WILLIAM L. BRADLEY FUND

BY

THE UNIVERSITY PRESS

CAMBRIDGE

1921



LANDSCAPE
ARCHITECTURE

Add'l
Farrand Gift



LANDSCAPE
ARCH.
LIBRARY

PREFACE

THE value of Azaleas as garden plants in the eastern United
States, where few of the Rhododendrons with persistent leaves
can be successfully cultivated, has led to the critical studies of
these plants which appear on the following pages.

Mr. Wilson's long journeys in eastern Asia has made it pos-
sible for him to study all the species of the Japanese Empire
and China as wild plants, and to become familiar with the
Azaleas growing in Japanese gardens. For many years the
Arboretum has been engaged in a field study of the American
species, and has been able to place at Mr. Render's disposal
the large amount of material which is preserved in this her-
barium, and which has been supplemented by that contained in
other American collections.

The Azaleas of northern Japan and Korea, and of the
northern United States, are already growing in the Arboretum,
but the gardens of the southern states and of California have
still much to gain by the introduction of the species of the
southern states and those of southern Japan, China, and
Formosa, and this publication will not have accomplished its
purpose if it fails to induce the more general cultivation of
these plants in the United States and Europe.

The art of the hybridizer has produced many interesting and
beautiful Azaleas. Imperfect records have made the study of
many of these hybrids difficult and uncertain, and this difficulty
is increased by the fact that many of them are no longer culti-
vated unless, having escaped the change of fashion in plants,
they are still growing in English gardens, planted about the
middle of the last century, and I venture to suggest to my
associates in the English Rhododendron Society that the study
of Azaleas in European gardens might add much to the knowl-
edge of the origin and value of many of these plants.

C. S. SARGENT, Director.

ARNOLD ARBORETUM
MARCH, 1921.



609



TABLE OF CONTENTS

PAGE

PREFACE . > * v

THE AZALEAS OP THE OLD WORLD. By Ernest Henry Wilson . 1

THE AZALEAS OF NORTH AMERICA. By Alfred Rehder .... 107

DOUBTFUL NAMES 197

OAQ

ILLUSTRATIONS

ADDITIONS 206

INDEX. 207



THE AZALEAS OF THE OLD WORLD

BY

ERNEST HENRY WILSON



THE AZALEAS OF THE OLD WORLD



INTRODUCTION

BOTANISTS may hold different views on the classification of
the subdivisions of the large genus Rhododendron, but garden-
ers and lovers of plants in general have no difficulty in recog-
nizing Azaleas as distinct from other groups of the genus. It
is hi the popular rather than in the strictly technical sense that
the title of " Azaleas of the Old World " is applied here. These
plants with few exceptions are sun-loving; and their wide popu-
larity among the peoples of the Orient, of America, of Europe
and Australia is due largely to the brilliancy of their flowers,
their floriferousness and the ease with which many of them can
be cultivated. In the Orient they have been favorite garden
flowers from very early times and in the Occident for more than
a century some have been familiar and valued greenhouse plants,
and in recent years it has been found that several are more
hardy than they were generally supposed to be. In the Arnold
Arboretum such hardy kinds as R. obtusum var. Kaempferi and
R. japonicum are among the most satisfactory and most beau-
tiful of Asiatic plants. Farther south and in California the old
Azalea amoena and A. ledifolia and the newer "Hinodegiri" are
much grown in gardens. Others are less known, but I believe that
in the near future both in increased variety and in quantity
Azaleas will have a much more important place in gardens. In
certain groups the hybridists in Europe have wrought wonder-
ful results, and the field is still full of promise. In Japan, in the
city of Kurume, selection and raising from seed has been in
progress among a single group for a century, and these plants are
now beginning to find their way into the Occident. With these
facts in view the need for a critical survey of the species and
forms seems necessary. Through confusion with other species
and for lack of accurate names many good plants have become
lost from our gardens, and others for the same reason have not
been introduced. During my travels in China I greatly admired

l



2 THE AZALEAS OF THE OLD WORLD

the red-flowered Azalea of the country so abundant on the hills
from the coast to the extreme west, from near sea-level to 1300 m.
altitude. So common is it that in May much of the country-
side is a blaze of red. For years I unhesitatingly accepted this
plant as the Azalea indica of Linnaeus, considering the differ-
ence in the number of stamens an unimportant triviality. In
1912-13, when working up the Rhododendron material for Sar-
gent's Plantae Wilsonianae in conjunction with my colleague,
Alfred Rehder, I became conscious that all was not so simple
as I had assumed. The question as to what Azalea indica really
was began to arouse my interest. On the occasion of the Arnold
Arboretum Expedition to Japan in 1914 I devoted much time
to the problem, and in Yaku-shima in February collected an
Azalea which later I discovered to be the true Azalea indica of
Linnaeus. I questioned many botanists in Japan, but none at
that time had any definite views on the subject. Nevertheless,
by deduction and comparative study I arrived at the conclusion
that the group of Azaleas cultivated in Japan under the name
" Satsuki" all belonged to Linnaeus' species and that the ma-
terial collected in Yaku-shima was its wild parent. On my re-
turn to the Arnold Arboretum early in 1915 I critically com-
pared the material I had collected with Linnaeus' description
and with the old figures on which his species was based, and the
proof of this theory was absolute.

Japan is so rich in Azaleas, both wild on the mountains and
cultivated in gardens, parks and temple grounds, that at the
end of 1914 I felt that beyond establishing the identity of
Azalea indica I had acquired no more than a moderate working
knowledge of the group. My interest, however, was keener than
ever. Being favored with another opportunity to visit the
Orient I determined to devote as much time as possible to the
study of these Azaleas. During 1917 and 1918 I visited many
places famous in Japan for Azaleas and gathered specimens and
information from all sides. On my visits to Korea, Liukiu and
Formosa I collected much new material. The result is that on
my various visits to the Chinese and Japanese Empires I have
seen growing wild, with few exceptions, every species known
from those regions and almost every known variety and garden
form. In Japan in 1914 and again in 1917-18 I received in-
estimable assistance from Mr. H. Suzuki, President of the



INTRODUCTION 3

Yokohama Nursery Company and one of the foremost horticul-
turists in Japan. Together we visited Mt. Kirishima and the
famous Azalea district of Kurume in Kyushu, also those near
Osaka and Tokyo. He introduced me to all the leading special-
ists, gave of his own store of knowledge freely, and without
his help it would have been quite impossible to have delved so
deeply into the cultivated Azaleas of Japan. It is with keen
pleasure that I acknowledge my indebtedness to this genial and
scholarly gentleman. I know not how many hundreds of speci-
mens of my own collecting have been available for this work,
and in addition, through the courtesy of the Director of Kew
and the Keeper of the Gray Herbarium of Harvard University,
I have had on loan all their material, so rich in old types of these
Azaleas. In Tokyo, through the courtesy of Professor J. Matsu-
mura, I have examined the material preserved in the Herbarium
of the Imperial Botanic Garden. Dr. Merrill has kindly loaned
me the material preserved in the Herbarium of the Bureau of
Science, Manila. To Dr. T. Nakai I am indebted for much
useful information relative to certain critical Azaleas to which
S. Komatsu has recently given names with brief descriptive
notes in Japanese.

The study of long-cultivated garden plants is exceedingly
complex, and to fathom some of the problems is almost beyond
human skill. This statement is as trite as it is true, and I freely
confess that I have found the problems presented by many of
these Azaleas more intricate than those of the Japanese Cherries.
Notwithstanding my unusual opportunities in the field and in
the gardens of the Orient and the abundant herbarium material
at my command I should have been ill equipped for the task
but for the collection of living plants cultivated for nearly three-
quarters of a century on the Sargent estate in Brookline, Mass.
This collection has been zealously maintained and is rich in old
garden types introduced through Fortune and others, some of
which have apparently been lost in Europe. Professor Sargent's
knowledge of these Azaleas is profound, and it is under his sym-
pathetic guidance and help that this little treatise has developed
from chaos to order, and to him most largely is due what merit
it contains.



HISTORY

THE cultivation of plants and the development of gardens is ever a
sign of a nation's advance toward culture and refinement. How early
this art began in the Orient we do not know, though history tells us
that plants like the Yulan and Moutan Paeony were highly esteemed
garden flowers among the Chinese during the Tang Dynasty (618-
907 A. D.)- It is much to be regretted that we are so ignorant of the
early history of China. It is known that during the Han Dynasty
(B. C. 206-A. D. 25) the Chinese had intercourse with India and Zan-
zibar. If proof were needed of their visiting these countries at an early
period it is supplied by the presence in south China and Formosa of
such typical African plants as Cactus-like Tree Euphorbias. Such
species as E. triangularis Desf., E. neriifolia L. and E. tirucalli L. are
common hedge-plants and are naturalised in certain places like Hong-
kong, Kowloon and elsewhere in China, and near Takao in Formosa,
as they also are in parts of India. In point of fact E. tirucalli was
named by Linnaeus from material which came from India. Did we
know more about the early travels of the Chinese it is possible that
we should find that they were acquainted with America long before
its discovery by Columbus. In south China, Formosa and the Liukiu
Islands A gave fourcroydes Lem. is naturalised, but this may have been
introduced by the Portuguese, and so too may have been Maize and
Tobacco. Much more difficult is it to account for Opuntia Dillenii
Haw. naturalised and abundant not only on the Yunnan plateaux but
in the valley of the Tung River in a remote part of extreme western
China. It is significant also that Boym in his Flora Sinensis published
in 1656 figures such characteristic American plants as the Pineapple
(Ananas saliva Schult. f.), the Sweetsop or Custard Apple (Anona
squamosa L.) and the Guava (Psidium guajava L.), which were evi-
dently common plants in China when he was there (1642-53). In
what era the love for flowers began to manifest itself in Japan is un-
certain, but Buddhism in its Chinese form was introduced from Korea
about 552 A. D. and from then until the 8th century Korean and
Chinese monks and nuns visited Japan for purposes of proselytism.
From the 8th century onward it became more usual for the Japanese

4



HISTORY 5

monks to go to China in order to study the doctrines of the best ac-
credited teachers at the fountain-head. These monks introduced into
Japan a number of favorite trees and shrubs like the Ginkgo, Yulan,
Moutan Paeony, Chinese Quince, the Tea-plant, Buddha's Tree
(Tilia Miqueliana) , Sophora japonica, Prunus tomentosa, P. japonica,
Paulownia tomentosa, such fruit trees as the Peach, Apricot, Persimmon,
Pear, Apple, Plum, Cherry, Loquat, the Orange and its relatives and, in
all probability, the Chrysanthemum also. Though they probably did
not originate the love for gardens these monks must have greatly stimu-
lated it. The mutual love of flowers among the peoples of the Orient
induced and fostered the introduction of plants from one country to
another in the Far East even as it did in the Levant and, in later days,
as it has in the Occident. And so we find the history of garden plants
intimately associated with the social life of the peoples. We know
nothing of early intercourse between the Japanese and Chinese prior
to the introduction of Buddhism to Japan. We do know that Chinese
monks introduced their favorite flowers to Korea, that Chinese and
Korean monks carried them to Japan, and it is safe to assume that
these same monks and their Japanese disciples carried to Korea and
to China plants of Japan which appealed to their aesthetic sense. In
fact the presence in temple-grounds and other sacred places in China
of the Cryptomeria, which is endemic in Japan, and of many varieties
of Japanese Camellias and Azaleas in Chinese gardens, is positive proof
that Japanese plants were long ago introduced into China.

The illustrious Venetian, Marco Polo, who lived many years in
China during the latter part of the 12th century and to whom we owe
the first authentic account of that mighty empire, notices from his
own observation many of the vegetable productions of China used
for economic purposes. After his memorable travels China was for a
long time closed to European access and had been altogether forgotten
in Europe when in 1516 the Portuguese first arrived in China. The
Portuguese claim the honor of having first introduced the Sweet-
Orange from China to Portugal some time between 1545 and 1548.
About the end of 1542 the Portuguese adventurer, Mendez Pinto,
discovered Japan, first touching at the island now known as Tanaga-
shima south of Kagoshima in Kyushu. The Portuguese made their
way north as far as Oita in northeast Kyushu where Mendez Pinto
in 1543 received a friendly reception from the local Daimyo. The
arquebus Pinto carried astounded the Japanese, who had never before
seen any explosive weapon. In 1549 St. Francis Xavier reached Japan



6 THE AZALEAS OF THE OLD WORLD

and introduced Christianity; he visited Oita, and going north to Hondo
established a mission at Yamaguchi, a few miles north of Shimonoseki.
This newly introduced religion soon claimed thousands of adherents,
much to the alarm of the Japanese Daimyos and military men backed
by Buddhist priests, and a period of persecution commenced. The
native Christians migrated to Nagasaki, which soon became one of the
chief marts of Portuguese trade.

In 1596 the Dutch first visited Java and other islands of the East
Indies and in 1602 the Dutch East India Company was established.
The war which then ensued between the Dutch, Spaniard and Portu-
guese for possession of the spice islands lasted until 1610 when the
Dutch remained master of these seas. The seat of the Dutch govern-
ment was first established on the island of Amboyna, but in 1619 it
was transferred to the newly founded city of Batavia in Java. In 1600
a Dutch ship visited Japan, and nine years later the Dutch East India
Company sent several vessels to Firando (Hirado), northwest of Naga-
saki, where they were well received by the Japanese. In 1611 a formal
edict in favor of their trade was obtained. A Dutch factory and also
an English factory were established at Hirado the same year.

In 1624 Christianity was proscribed in Japan and the land was
closed to foreigners. The Portuguese, English and Spaniards, who also
had a factory, were expelled and only the Dutch and the Chinese were
permitted to carry on trade, and that under galling restrictions. The
Dutch factory was removed in 1639 to Deshima, then an islet at the
head of Nagasaki harbor but now absorbed into the foreshore. And
so Japan secluded herself for over two centuries from contact with the
outer world until the advent of the American Expedition in 1853-54
under command of Commodore Perry. All this may seem to have
little to do with plants and with Azaleas in particular and yet they
are inextricably bound up with the subject. It is to the merchant
adventurer that we owe all our first plant introductions from Japan
and our early knowledge of the flora. From 1690-92 Engelbert
Kaempfer, in the service of the Dutch East India Company, lived in
Japan, and in his Amoenitates Exoticae, published in 1712, he gives an
admirable account of Japanese plants. He gives good figures of many
of these under the vernacular names and among them an Azalea now
known as R. obtusum var. Kaempferi Wils. In all Kaempfer mentions
twenty-one Azaleas, and it is interesting to note that many of the
vernacular names he gives are in common use to-day. C. P. Thunberg
in 1775 visited Japan in the capacity of physician to the Dutch Com-



HISTORY 7

pany and in 1784 published his Flora Japonica, the first post-Linnaean
work on the flora of the Orient. Thunberg mentions the Azaleas under
their vernacular names and relegates them all to Azalea indica. Ac-
cording to Juel (PL Thunb. 391 (1918)) they represent R. obtusum
Planch., R. japonicum Suring. and R. mucronatum G. Don.

Lastly in this connection mention must be made of Philipp von Sie-
bold, who joined the service of the Dutch East India Company and
lived at Deshima from 1823 to 1829. To him we owe the magnificent
Flora Japonica; also he introduced about 1830 such ornamental plants
as Lilium elegans and L. speciosum from Japanese gardens, and, twenty
years later, several others including Mains floribunda, M. Sieboldii
and certain flowering Cherries.

About 1677 the English East India Company established a factory
at Amoy and in 1684, after a conflict with the Portuguese, one at
Canton. Through this company many Chinese plants were introduced
to India during the 18th century and early in the 19th century to
England; they include several Azaleas. However, in China the Jesuit
priests were the first to inform us about the flora of the land. In 1790
Joannis de Loureiro, a Portuguese, published his Flora Cochinchinensis
and mentions one species of Azalea (A. punctata), but this remains an
obscure plant and may not belong to the genus.

During the last quarter of the 17th century Jakob Breyne, a
merchant of Danzig and a distinguished botanist, visited Holland and
saw growing there several famous garden plants of the Orient which
he duly records in his Prodromus Plantarum. On page 24, pt. I, pub-
lished in 1680, we read " Chamaerhododendron exoticum amplissimus
floribus liliaceis. Frutex spectabilis elegans. In horto Beveringiano."
This is the plant on which Linnaeus (Spec. 1753) bases his Azalea
indica. Breyne does not say from what country this shrub had been
brought, but P. Hermann, in his Academici Horti lugduno-batavi
catalogue, p. 152 (1687), describes the same plant under the name of
"Cistus Indicus Ledi alpini foliis, floribus amplis," figures it on page
153, and reports that it was introduced from Jaccatra, which is Ba-
tavia, in Java. No species of Azalea grows in India, and it has been
generally supposed that this Azalea had been brought to Batavia by
the Chinese, but I am of the opinion that it was taken there from Japan
by Dutch traders. In the gardens of Nagasaki and elsewhere, then
as now, it was a common garden plant and, moreover, it is indigenous
in the warm southern parts of Japan. That at the early date men-
tioned plants from Japan were growing in gardens in Holland is certain,



8 THE AZALEAS OF THE OLD WORLD

and the Tea-plant was introduced from Japan about 1689. Breyne
(Prodromus, I. 4) states that he saw in the garden of Hieronymus van
Beverningk in 1678 a fine specimen of the Camphor-tree which had
been introduced from Japan. Again, in his Prodromus, II. 66 (1689)
Breyne tells of six varieties of Chrysanthemum from Japan which he
saw growing in Holland gardens. All these early introductions seem
to have been lost. I have carefully looked through many old books
of the 18th century and I find no references to any species of Azaleas
being in European gardens, and they appear to have been unknown in
Europe at the close of the 18th century. The one oriental species was
known to Linnaeus through the books. In Batavia, however, several
were grown, as we know from the writings of Burmann and Blume.

In Aiton's Hortus Kewensis (1810) Azalea indica is stated to be in
cultivation in Kew, having been introduced from China in 1808 by the
Court of Directors of the East India Company in the ship "Cuffnels"
Captain Wellbank. This plant was Rhododendron Simsii Planch., and
here began a confusion between Linnaeus' species and the Chinese
Azalea which still survives. Through the activities of officers of the
East India Company at the close of the 18th and the beginning of the
19th centuries English gardens were enriched by many Chinese plants.
No officer was more active in this work than John Reeves, who as
Chief Inspector of Tea in the Company's establishment at Canton
resided in Macao and Canton from 1812 to 1831. He was either the
immediate or indirect source from which our gardens derived Camel-
lias, Moutan Paeonies, Chrysanthemums, Roses, Wistaria sinensis
and many Chinese Azaleas including R. Farrerae Tate, a pretty Hong-
kong species, and also R. phoeniceum G. Don, destined to be of so
much value as a stock on which to graft " Indian Azaleas," so called.

In 1818 or 1819 Samuel Brooks, a nurseryman at Ball's Pond, New-
ington Green, sent out to China Joseph Poole, a gardener, and through
him secured among other plants Azalea indica alba (R. mucronatum
G. Don) and Azalea indica purpurea plena (R. mucronatum f.
plenum Wils.). In 1823 Azalea sinensis (R. molle G. Don) was
received from China by Loddiges of Hackney and by William Wells,
nurseryman, of Redleaf. In 1832 Joseph Knight, nurseryman, of
Chelsea, London, secured Azalea indica variegata (R. indicum f.
variegatum DC.) and A. indica lateritia (R. indicum Sweet) brought
home from China by Mr. M'Killigan. In 1821 Rhododendron Farrerae
was reintroduced and in 1832 R. indicum var. ignescens Sweet, both
through Captain Farrer of the East Indiaman "Orwell," who gave



HISTORY 9

them to Tate, a nurseryman, of Sloane Square, London. In the Botan-
ical Register, t. 56 (1842), is figured a double red-flowered Azalea said
to be of Chinese origin and in the possession of William Wells, Esq.,
of Redleaf . These various Azaleas by hybridization and selection soon
became the parents of a number of good plants which are figured in
the periodicals of the time. Especially valuable was the Azalea indica
variegata which in the hands of Knight, and of Ivery, another English
nurseryman, yielded several very ornamental varieties.

In 1843 Robert Fortune was sent to China by the Horticultural
Society of London, and his travels and explorations there, which ended
in 1861, inaugurated a new era in the history of plant introduction
from that country. He sent from Chinese gardens at Shanghai and
elsewhere to England many Azaleas, including such new ones as Aza-
lea obtusa (R. obtusum Planch.), Azalea ramentacea (R. obtuswn
f. album Rehder), Azalea crispiflora (R. indicum var. crispiflorum
Schneid.), Azalea amoena (R. obtusum f. amoenum Wils.), Azalea
narcissiflora (R. mucronatum f. narcissiflorum Wils.), Azalea vit-
tata (R. Simsii var. vittata Wils.) and Azalea Bealii (R. Simsii
var. vittata f. Bealii Wils.). There is no need to emphasize the value
of these new Azaleas. His vittata with lilac flowers and Bealii with
red-striped flowers gave an impetus to the raising of new forms and
may be said to have initiated an industry which has resulted in the so-
called race of " Indian Azaleas." The true R. indicum, whose progeny
are not amenable to forcing, dropped out and the forms of R. Simsii,
R. mucronatum and R. obtusum seminal, branch sports and hybrids



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