I've heard that planting them close together helps support them, but that seems to me to be a poor trade, of more support for less root zone. I've also heard that while pepper foliage like heat, their roots like to be cooler, hence an advantage of soil shading. There may be something to that, because peppers are less tolerant of moist soil than tomatoes, and moist soil is cooler soil. Some shade would also help avoid sunscald.

These have never been issues for me, though.

First of all, without enough sunlight, you'll never get "max yield". However, you may still be able to get an "acceptable" yield. How much light do you get?

Also, are you planning to use the cold frame all season? If so, you risk burning the plants to the point of death. Summer heat should be more than enough, even in Ohio I would imagine. Getting an early start or keeping them going late into the fall is where cold frames come in. Keep the cold frame off if it's warm enough.

As for spacing, any plant spaced too closely, or "crowded", will not perform well, and you will have to face many issues such as disease pressure due to lack of airflow, weak plants due to not enough nutrients in the given area, etc. We've always spaced our peppers 12-24" apart depending on the variety. Some, like our chili peppers, can be spaced at 12-18" apart, as they don't grow large, and that is assuming full sunlight. Our bigger bells (e.g., Big Bertha) would very much appreciate 2-3 feet, as they get to be absolutely large plants. Again, it all depends on the plants.

As a rule of thumb, look at how large the plant will be, and space at the spacing that you absolutely feel will be sufficient at maturity. If you see the plant will have a spread of 36", space at the spacing to give it that much spread without being pressured by other plants, etc. By all means, do some experiments and see how your plants fare with different spacings.

Another factor: every climate is different, thus affecting even spacings. Over here with our intense summer heat, planting a tiny bit closer could possibly be beneficial, providing a little shade for the roots. Assuming it doesn't get quite as hot in Ohio with that Great Lake influence, I'm sure wider spacing would help, allowing the sunlight to get to the soil, thus warming it up more and extending the season length.

Again, how much light do you get where you plan to place your peppers? This could affect spacings, causing you to space them farther apart, but then again, in the shade, more plants closer together might equal more yield altogether, as they certainly will not maintain maximum production per plant no matter how you grow them in the shade.

Hope this helps.

I just try to space my peppers as to how much space they take up by summer's end, if they're kissing that's ok. Tomato cages at the Home Improvement stores work great for peppers.....not so much for tomatoes, not at all.

If you get full sun most the day, then peppers should do great there. 10-12" is a good spacing for smaller peppers like chilis, but not quite enough for larger plants likely.

Also keep in mind that many backyard gardeners are looking more for yield per given space, rather than yield per plant.

For example... if, in a 4' wide bed, starting 6" - 8" in from the edges, I plant 3 plants across the width, that gives me 16" - 18" spacing. For the next set, I can either repeat the 3 across, or do a checker board pattern and plant 2 across the width (reducing the distance from the 3-across set to 12" along the length, but keeping almost 18" between plants. I'll then repeat the pattern along the width of the bed... 3 plants across, 2 plants across, 3 plants across... etc...

In either the continual 3-across, or the 3, 2, 3, 2, by the time the peppers are ready for harvest, the entire bed will be completely filled with growth. What does this gain? Yield for each plant might be slightly less than plants given a little more space, but such intensive planting will usually have garnered more weight per sq. ft. Each individual fruit may be smaller, but in most cases, the weight yield per space will be higher. This technique is old, but has been proven time and again by indoor grow operations.

Now.. the pros and cons, caveats and potential downsides...

Peppers, like many produce, are used for different purposes. I almost always cut up my peppers before using them. That means I don't care how big each pepper is, I want high yield per space (even if it means smaller fruits.) If however, you like stuffed peppers - or some other dish where the pepper is used whole, you may want to grow a few plants with a little more elbow room between them. This will maximize fruit size.

Intensive planting also raises the chance for disease incidence. Peppers are not too bad for diseases here, so I haven't had to worry, but area where diseases are high may want to increase space as necessary.

As mentioned above, the more intensive the planting, the higher the demand for nutrients and water. Since they are somewhat forgiving for these needs, I find that intensive planting works well for peppers. I should add that my ground is fairly fertile, and those who have amended with lots of compost usually have little issue with P or K. And while peppers need enough N for optimum production, I find that too much N can lead to lots of foliage. I don't starve N, but neither do I like to give them unlimited amounts.

Very very good points. Better use of space, that did not occur to me. My plants were 12" apart but only 2 rows in a 4 foot wide bed. The plants did great - I just can never get enough peppers!

I space my peppers in row according to the maximum width of the tomato cages I use to support them which IIRC is 15" at the top.

One way to get more production out of a given area while giving your peppers plenty of space is to plant them farther apart and plant something quick in between, like lettuce or dill or anything that will be finished by the time the peppers spread out.

I do thanks! Garlic there now, maybe some lettuce etc. That said my peppers are really important - never have as many as I can use! Most others things I get plenty.