Four Rules for Using Ground Covers:

Creeping Phlox

Pachysandra

The uses of ground covers are nearly endless, and are limited only by your imagination. Even so, you should always attempt to follow the four basic rules of ground cover use. Adhering to these four rules will prevent the use of inappropriate or incompatible ground covers and will insure optimal success.
Combining too many different types of ground covers in the same landscape results in a busy, cluttered appearance. To create the most appealing landscape, use only one or a few selected varieties.

In general, plant large-leaved ground covers when the scale is large, and small-leaved ground covers when the scale is small. By following this rule, you will create a harmonious setting, and your plants will always be in the proper proportion to the landscape. Doing the opposite will waste the precious little space of the smaller landscape or leave the large setting looking naked.

Sensitivity to companionship should be exercised when combining ground covers with other plant types, such as trees or shrubs. In other words, you should only install plants which will comfortably coexist. Such plants should possess not only similar cultural requirements, but complementary colors, textures, forms, and sizes. If plants of different compatibility (companionship) are planted together, not only will harmony be lacking, but extra maintenance will be required.

Never combine ground covers that have incompatible growth habits. The worst offense in this regard is to combine a species of vigorous, horizontal spreading habit (such as English ivy, periwinkle, Goutweed, or fleece flower) with a species of diminutive or refined habit (such as Stonecrop or Germander). The vigorous plants will soon overrun the smaller, slower growing ones.