I've done 15-16 in cages with no ill effects just to fit another plant in a row, but 18 is what I do. I don't believe in the close together thing. I used to get a colored bell that got sunscald now and then, but now I just do the shading myself. When it gets THAT hot, it's just as important to try to keep the soil cool also. So, shade cloth in the middle of the day is my norm when the heat really kicks in.

Kevin

I do 18" apart and they thrive (full sun and breezy).

Carol in RI (zone 6=7)

I've done 1sf in SFG. It's tight though and will overgrow it's square a bit

Same here - 16-18" in the gardens. I have planted 2 much closer together in a 15-20 gallon container but they didn't produce nearly as well. Of course that may have been partly the fact they were in a container too.

I don't know if sun scald is as beg an issue in Ohio as further south but if the plant gets the proper nutrients it should shade itself.

I have had occasional sun scorching here in N Ohio, but it's not a problem as it only hits a couple peppers every few years. And I have never had a disease problem with peppers.

Lately, we have gone to growing the small, sweet chilies and only a few bell peppers. We save the seeds every year. They have thick walls like a bell pepper and taste sweeter. They average 2" to 3" long, are early and prolific, and the small ones can be eaten like gum drops as they are uvirtually seedless. We have red, yellow, and orange, and use them just like bell peppers except for stuffing. If I'm activee enough this winter, I will try to offer some on the seed exchange.