26 
been more largely planted and better cared for in the neighborhood of 
Boston than in other parts of the country; and judging by the best 
collection in America, at least, of the so-called Catawbiense hybrids 
on which incessant care, intelligence and money have been expended 
continously for seventy years the results which can be obtained from 
the cultivation of these plants in New England are not great in com- 
parison with the results obtained in regions better suited to their 
requirements. 
Rhododendrons usually grow on mountain slopes where, although the 
atmosphere is saturated with moisture, their roots are in well drained 
soil, and where they are often protected in winter by snow. Here in 
New England they grow best when planted on the north side of ever- 
green trees, protected from the stimulating effect of the hot sun of 
March which excites growth and increases the danger from late frosts. 
Planted in such a position at the base of Hemlock Hill in the Arbore- 
tum there are good plants of Catawbiense hybrids. Rhododendrons are 
not particular about soil provided it is well drained and is free of lime. 
A few of the new Chinese species grow naturally in limestone soil, 
but none of them are hardy in the eastern states. For the Rhododen- 
drons which can be grown here lime is fatal, and persons who go on 
year after year trying to overcome this peculiarity of nearly all plants 
of the Heath Family are throwing away their labor and money. Rho- 
dodendrons suffer from insufficient moisture at the roots and cannot be 
safely planted within reach of the roots of vigorous trees which de- 
prive them of it. In recent years Rhododendrons in the neighborhood 
of Boston have been injured by the lace wing fly, an insect brought 
from the south on collected plants of Rhododendron maximum, which 
discolors and kills the leaves and finally, if unchecked, the plants. 
This insect can be killed by any contact spray, but as they remain on 
the lower side of the leaves it is not always easy to reach them on 
large plants. Shade is unfavorable for their increase and they are 
more numerous on the southern than on the northern side of plants, 
and on plants growing in the open. Three or four broods are hatched 
in one season, and this means that the plants must be constantly 
watched and sprayed several times during the summer. 
The species of Rhododendrons which have proved hardy here are the 
eastern American R. maximum, R. catawbiense, R. minus and R. car- 
olinianum, the European R. ferrugineum and R. hirsutum, the Cau- 
casian R. Smirnowii, the Chinese R. micranthum and the Japanese 
R. brachycarpum. The four American species are perfectly hardy and 
can be grown without dilficulty. R. maximum is the largest of these, 
becoming sometimes a small tree in the sheltered valleys of the south- 
ern Appalachian mountains. It has beautiful, dark green, lustrous 
leaves pale on the lower surface, and clusters of pink and white flow- 
ers which do not open here until July and are a good deal hidden by 
the branches of the year which have nearly finished their growth be- 
fore the flowers appear. R. catawbiense is a round-topped shrub with 
beautiful foliage and lilac purple flowers of a distinctly disagreeable 
color. It grows on the southern Appalachian Mountains, sometimes 
covering near the summits of the highest peaks, at altitudes of between 
five or six thousand feet, thousands of acres with impenetrable thick- 
ets; it occurs, too, sparingly in the Piedmont region of North Carolina, 
