These rapid-growing trees have value in certain places in parks and on large places. The true white poplar of east Europe makes a large tree with silvery foliage. It does not sprout as much as the gray poplar or abele of west Europe. In the centre of a large group, or at an angle or corner, it gives variety of expression in contrast, as Downing says, with darker-foliaged species. If the sprouts are pulled up as they appear the tendency to sprout does not last long. But if cut off they grow stronger than before.
The variety Bolleana also sprouts but little. This is upright in habit and is only admissible where trees with silvery foliage and upright habit are wanted to fix attention to a particular point in the landscape.
Populus certinensis of east Europe has a fine pyramidal habit, with large heart-shaped dark-green leaves with wavy or folded edges. It can be used everywhere to give variety to groups of quick-growing trees.
The willows also have certain uses. In large cemeteries and near water such weeping varieties as Babylonica. Kilmarnock, Thurlows, Purpurea, and Napoleonis of the catalogues are useful and give much variety to scenery.
At the West the Napoleonis top-worked on Salix aurea is most valuable together with the Wisconsin weeping, as the others named above are not hardy North of the 42d parallel.
For holding the banks of ponds and streams the small-leaved brook willows are often useful and ornamental, and can be started by sticking cuttings into the banks.
Among ornamental willows with rounded tops and handsome foliage the two best are Salix aurea and Salix lauri-folia.
TJie Salix aurea as received frcm Russia is far better than the common golden willow, as its leaves are shining and its growth in winter has much brighter golden color that can be seen from afar. Salix laurifolia from European Russia has been most used at the West, but its value in giving variety of expression to round-topped groups is now being generally recognized.
As a shrub willow for group undergrowth and stream borders, the value of Salix rosemarinifolia is not as yet fully recognized. Its narrow rosemary-like leaves are quite showy. The east European variety is hardy on upland in the West.