That all depends on you're goals.. If youre looking to create a sea of green.. yea, that spacing will work well but you wont be able to get to each plant in the later stages to check for problems.. it will be to crouded. if you have large holes you could grow large plants where the spacing should be adequate for maintance. mine are six feet apart and the plants are already closing the gap. it is a little to tite.. i think next year ill be going eight feet apart. but I have all the room in the world to work with.
It's best to make each hole at least 2x2x2 and at least 3-5 ft apart. I plant my girls more like 10 ft apart to give them room to spread. If they are too close together it will really hurt your yield per plant because your roots will be competing and they will block the light to each other. I know this from making the mistake of planting to close together myself. My first year growing in ground I totally underestimated how big my plants would get. It's a totally different ball game than growing indoors or outdoors in containers. If you're trying to start outdoors this late this season they don't need to be as far apart as mine because they don't have time to get very big. Edit- actually my first 2 years growing outdoors in ground I planted to close together. The first year I had them about 1 ft apart and that was way to close. The second I planted about 3 ft apart and they still way outgrew the space they had. The more grows I have under my belt, the more I learn. And I hope I never stop learning.
^^^ she knows what shes talking about ... since your planting late in the season you should seperate them ateast 1-2 meters apart ... mix you ground soil with peat and perlite ... have the soil breath properly ...