Answer: Vinca minor spreads quite rapidly. How closely you'll space them will depend upon how quickly you want the area to fill in. 4" pots of Vinca are typically an 8" wide plant. You'll want want to space these about 12 inches apart. One-gallon containers will have plants spreading out about 12". You'll want to space these two and one-half to three-feet apart. A full flat will yield about 36 small plants. Space these checkerboard style, 6-8" apart. All you'll need to do is measure the site (length times width) to get the square footage and then decide what size plants you'll be purchasing. Divide the total square feet by the spacing required by the size plant you're buying and you should be able to figure out how many plants you'll need. If you're having trouble figuring it out, check with the nursery staff and they'll figure it out for you.
Best wishes with your project!
Q&A Library Searching Tips