They are simply shrubs. There is nothing colorful, unusual or spectacular about their foliage, and their flowers are basic white. But what the four shrubs pictured above do well is form a dark-green background for other plants. If the flowers in your garden lack a certain punch, it is probably because they don't have the correct background. Roses, a flowering shrub or a bed of annual or perennial flowers will appear more dramatic against this background of deep-green foliage. Light green, gray green or reddish or "bronzy" greens won't do. They draw attention to themselves and no longer serve as a backdrop. What we're talking about is a simple--but substantial--green.
Not too surprisingly, several of these simple green shrubs have long been appreciated. They have been favored since Roman times for the cooling effect that their dark-green foliage brings to the sun-baked gardens of the Mediterranean--though all four shrubs can tolerate considerable shade. Although they will not grow that densely, these shrubs will grow on the north side of a house or where they're partially shaded by a tree. The shrubs can also be pruned to shape, and they make fine hedges. All are easy to grow and are readily available. However, nursery plants are often root-bound from sitting unnoticed in a corner too long, and it is sometimes advisable to order fresh plants.