14 
and the Laurels. On Azalea Path the plants are fully exposed to the 
sun and the flowers, which are extremely delicate, soon wither. On 
Hemlock Hill where the plants are in partial shade they flower a week 
or ten days later, and the flowers remain longer in good condition and 
make one of the brilliant flower shows of the Arboretum year. 
Rhododendron poukhanense. This is the Azalea which Mr. Jack in- 
troduced into the Arboretum from Korea. When it first flowered here 
it was described as R. coreanum before it was known that a French 
botanist had already named it for Poukhan, a Korean mountain where 
it had been found by a French missionary. It is a beautiful round- 
topped, compact shrub, with large, rosy pink, fragrant flowers. It 
appears to be ^perfectly hardy in the most exposed positions, and has 
flowered freely now in the Arboretum for several years. A double- 
flowered form of this plant, sent to this country from Japanese nur- 
series under the name of Yodogaiva is a form of the Korean plant. A 
number of plants of R. poukhanense are now flowering on the upper 
side of Azalea Path. 
Chinese Poplars in early spring. The beauty and interest of several 
of the Poplar trees of eastern Asia is increased by the bright red- 
bronze color of the young leaves. The unfolding leaves of Poplar trees 
from other parts of the world are not colored in this way, and those of 
P. Maximowiczii, P. suaveolens, P. tomentosa, P. Simonii, and P. yun- 
nanensis of eastern Asia are green as they unfold. The young leaves 
of the other Chinese species, P. szechuanica, P. Wilsonii, P. adenopoda, 
P. lasiocarpa, P. tremula, var. Davidiana and its form tomentella, and 
the Japanese P. Sieholdii are all more or less deeply tinged with red. 
All the eastern Asiatic Poplars are now growing in the Arboretum 
with the exception of the Chinese form (var. Duclouxiana) of the Him- 
alayan P. rotundifolia which has not been introduced, and they all 
prove to be hardy and fast-growing trees here with the exception of 
P. lasiocarpa which is not very hardy and suffers badly from borers 
here, and perhaps P. yunnanensis which has not been sufficiently tested 
yet in the Arboretum. 
Hydrangea petiolaris. This vigorous Japanese climbing plant has 
usually been planted in this country to grow up the trunks of trees, 
and it does not appear to be generally known that it is one of the 
best plants that can be used in this climate for covering brick or stone 
walls to which it clings tenaciously. In such situations it grows rap- 
idly and flowers more freely than when growing among the branches 
of trees. Its value as a wall covering is increased, too, by the early 
appearance of the dark green leaves which are nearly fully grown be- 
fore there is the sign of a leaf on any of the Virginia Creepers or 
other deciduous-leaved climbing plants which can be grown here. All 
Hydrangeas need plenty of water, and probably H. petiolaris will do 
better on the north or east side of a building than in a southern ex- 
posure. A large specimen can be seen on the Administration Building. 
