Ground cover plants should be spaced to ensure that they cover the area as quickly as possible to discourage weed establishment. Planting distance depends on the species selected and the individual plant characteristics (clumping, running, etc.). Small plants such as dichondra and Creeping Charlie may be set as close as 3-4 inches, while larger woody plants may be spaced as far as 4 feet apart. Asiatic jasmine, a highly popular ground cover, does well if placed at 2 feet on center. 

Additional Resource

http://edis.ifas.ufl.edu/EP016