The nice thing about ground cover is that there are multiple applications for it in a garden: edging and borders, between stepping stones, or erosion control. After the location has been decided, the next questions are what type of groundcover to use and how many. Today we are going to address the “how many” question.
How many groundcovers to plant is determined by the patience of the owner of the garden. If the desire is an instant landscape (not recommended) then the answer is a lot. If you can appreciate watching plants grow and mature over time, you can use fewer plants and save a couple nickels.
As a general rule of thumb in large plantings I would not plant any ground cover closer than 12” on center. Twelve inches on center is one plant per square foot. This can get very expensive very quick. Most all ground cover planted at twelve inches will fill in very easily in 1-2 growing seasons. Larger plant sizes like a 1 gallon sized plant can be planted at 24-36 inches.
For small areas like in between stepping stones I recommend low mat-forming ground cover. The mat-forming ground cover can be divided into smaller plants to fit awkward spaces and shapes. Spacing is not crucial for this application, just be sure to get plants in to all of the spaces between stones.
Ground cover also works well as weed control, once established. After the initial planting is done, the bare spaces between the plants are susceptible to weeds and weed seeds. Diligent maintenance is important for a weed-free planting. If that sounds like too much work, try a product called Preen. Preen is a pre-emergent weed control, preventing weed seeds from germinating and will not harm the plants you want in your garden.
Lastly, not all ground covers are created equally. Some are much faster growers than others. Avoid the fast growers in borders and edges. Keep in mind that ground cover does exactly that. I suggest starting with a small planting and make sure that you understand what the plant will do before going whole hog and being unhappy with the outcome.