The very name, "edging plants" indicates how these plants are used: they are grown along the edges of various features in the landscape; for example, the edges of driveways.
So to some degree, edging plants are defined by how they are used. But that still leaves us with a question: When landscaping your yard, how do you determine which plants are suitable for use as edging plants? Or to put it another way, how do you exclude the rest as being unsuitable? Well, in part, it depends on your personal tastes, as well as a variety of other factors, including:
- What you hope to accomplish by installing the edging plants
- The conditions (sun vs. shade, dry soil vs. wet soil, etc.)
- Your broader landscape-design goals (such as sticking to a particular color scheme)
Let's elaborate on #1 above, since it is not self-explanatory. Say you have, for example, a stone walkway that you use all the time to bring supplies from the garage to the house. You wish to soften its cold, hard edges with edging plants, but you do not want to impact the functionality of the walkway negatively. Consequently, you would use short plants, perhaps all of one species, massed together to achieve greater visual impact (some of the best choices here will be ground covers). You would also avoid plants that are messy, because having to clean up after them would add to your landscape maintenance.
However, consider the following case. Let's say the "edge" in question is the edge of your property: i.e., a property border. If you wish to define it with a row of plants, what you hope to accomplish in so doing may be entirely different than in the case of the walkway. It's not uncommon for homeowners to desire a living privacy fence along a property border, composed, for example, of tall shrubs.
Thus edging plants are also sometimes called "border plants." It's easy to see why, since in common parlance "border" can be synonymous with "edge." But it should be apparent from the foregoing examples just how much confusion can be caused by treating "edging plants" and "border plants" as synonyms. There's a monumental gap between the short plants used to edge a walkway and the tall shrubs required for privacy in a border planting. That's why I like to make a distinction between the two terms, calling the former "edging plants" and the latter "border plants."