There is always a temptation to use too freely of the trees and shrubs that are characterized by abnormal or striking foliage. The subject is discussed in its artistic bearings on pages 40 and 41.
As a rule, the yellow-leaved, spotted-leaved, variegated, and other abnormal "foliage" plants are less hardy and less reliable than the green-leaved or "natural" forms. They usually require more care, if they are kept in vigorous and seemly condition. Some marked exceptions to this are noted in the lists of trees and shrubs.
There are some plants of striking foliage, however, that are perfectly reliable, but they are usually not of the "horticultural variety" class, their characteristics being normal to the species. Some of the silver or white-leaved poplars, for example, produce the most striking contrasts of foliage, particularly if set near darker trees, and for this reason they are much desired by many planters. Bolle's poplar (_Populus Bolleana_ of the nurseries) is one of the best of these trees. Its habit is something like that of the Lombardy. The upper surface of the deeply lobed leaves is dark dull green, while the under surface is almost snowy white. Such emphatic trees as this should generally be partially obscured by planting them amongst other trees, so that they appear to mix with the other foliage; or else they should be seen at some distance. Other varieties of the common white poplar or abele are occasionally useful, although most of them sprout badly and may become a nuisance. But the planting of these immodest trees is so likely to be overdone that one scarcely dare recommend them, although, when skillfully used, they may be made to produce most excellent effects. If any reader has a particular fondness for trees of this class (or any others with woolly-white foliage) and if he has only an ordinary city lot or farm-yard to ornament, let him reduce his desires to a single tree, and then if that tree is planted in the interior of a group of other trees, no harm can result.