In general, you can plant spreading petunias about a foot or so apart, unless you are transplanting into a container, in which case you can crowd them a little more. Full sun and moist, but not waterlogged, soil is ideal. Some spreading types can cover an area 3 to 4 feet at maturity. See above article for general care. In general, deadhead any flowers that are withered and browning, to encourage blooming. Some spreading types, however, such as the Wave series, do not require deadheading for vigorous bloom.
In general, you can plant spreading petunias about a foot or so apart, unless you are transplanting into a container, in which case you can crowd them a little more. Full sun and moist, but not waterlogged, soil is ideal. Some spreading types can cover an area 3 to 4 feet at maturity. See above article for general care. In general, deadhead any flowers that are withered and browning, to encourage blooming. Some spreading types, however, such as the Wave series, do not require deadheading for vigorous bloom.