Answer: There are no real "rules" on how far apart to space annuals. They don't like to be jammed together but if spaced too far apart they won't fill your flower box they way you envision they will. They are quite forgiving in spacing where perennials are not, and I often "push the envelope". I grew New Guinea Impatiens last year, and I placed them quite closely together, each small plant perhaps as close as 4" apart. They looked great flowing out of the container. My New Guineas had a spread almost equal to their height(about 2 feet), given the right conditions, you can probably expect the same from 'Macarena'.
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