Arboretum News 
A Monograph of Azaleas, No. 9 of the Publications of the Arnold 
Arboretum. 
For thirty years Azaleas have been cultivated and critically 
studied at the Arnold Arboretum which has now published the 
results of these investigations, the Asiatic species being described 
by Mr. E. H. Wilson, the well known traveler in eastern Asia, 
and the American species by Mr. Alfred Rehder, the curator of 
the Arboretum herbarium. 
Azaleas, which botanists now call Rhododendrons, grow 
chiefly in eastern North America and in eastern Asia, one 
American species being found on the California Sierra Nevada 
and one Old World species occurring in the Caucasus and 
occasionally in the Balkan Peninsular. Among Azaleas are 
found some of the most beautiful of all flowering shrubs; 
several of the handsomest of them are perfectly hardy in 
regions as cold as New England, and all the species can be 
grown in the open ground in some part of the United States. 
In eastern Asia Azaleas with thirty-four species and many 
varieties grow naturally from Japan to western and south- 
western China, and from northern Korea to the mountains 
of Formosa and those of the Philippines. With the exception 
of the Philippine species Wilson has been able to see them 
all growing wild and to study the numerous forms cultivated 
in the gardens of Japan and China. Nearly all the Asiatic 
Azalea have been raised at the Arboretum from seeds and 
these specimens which are hardy in Boston are established in 
the Arboretum and contribute an important part to its spring 
flower shows. Only five of the Asiatic Azaleas however, can be 
really successfully gro^vTi in the northern states; A. Schlippen- 
tachii, with large pale pink flowers which open with the unfold- 
ing leaves, a conunon and widely distributed Korean plant still 
little known in gardens but the most beautiful of all Azaleas ; 
Azalea Kaempferi, with red flowers in different shades, when in 
bloom the showiest of hardy Azaleas ; A. Japonica, with orange or 
flame-colored flowers which do not open until the leaves are 
fully grown; the Korean A. poukhanen-se, with rose-purple 
flowers which open before those of the other Asiatic species, 
and A. reticulatuni, with dark rose-purple flowers. The 
beautiful white-flowered Japanese A. mucronata, better knoTvn 
perhaps as A. ledifolia or as A. indica alba, is often a feature of 
gardens on Long Island and in the south but further north can 
only be kept alive in exceptionally sheltered positions. 
In eastern America Azaleas are southern rather than 
northern plants, and eight of the sixteen species grow in the 
state of Georgia, but even in New England it is possible, with 
the seven species which are hardy in that part of the country, 
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