If you're in zone 5, this probably won't work, but peppers are perennials, so if you can keep them going over the winter, they'll launch right in to full production in early spring. That's what I do (barring a really bad freeze), and I get peppers in April!

I guess what you're asking about is whether you can get the peppers to launch into production early if the plants are more mature when you plant them outside. I don't see why not. That's essentially what I'm doing, except I just leave mine outside.

But peppers simply can't tolerate freezes, so when you're leaving them out in the open, you pretty much need to steer clear of freezing temps. Zone 5 would have the last freeze somewhere around mid-April. We just had a couple of nights below 26F, and I preserved my peppers by keeping them well covered.

In zone 5 having bell peppers early is going to be a challenge. Bells are not particularly very productive so you might want to look to other varieties of sweets. If you really want bells early then you're going to need to look to heated coldframes, low tunnels or greenhouse.

I planted a variety called Lady Belles from transplants. I had so many peppers I was giving them away and I only had 4 plants. They tolerated several bug attacks and diseases and never skipped a beat.

Starting too early brings its own challenges. Do you have a greenhouse or high-intensity lighting? I think you are starting your seeds at the right time, but perhaps need to use earlier varieties. Try Apple, Lipstick, New Ace, and a banana pepper.

I was going to suggest Ace or New Ace as well. They produce much earlier than most bell peppers and seem immune to variations in temperature, producing well regardless. Also, when we used to start all our own veggies, we used shop fluorescents set close to the plants in a bright window to start peppers in late February to mid-March, well before tomatoes. As the weather warmed, they would go out during the day (after careful hardening off by introducing them to the outdoors in part shade) since the air is so much warmer than the soil in May. Raised beds with row covers will warm up sooner and your peppers need warm soil to really put on good growth, so putting them in May 10 probably didn't help as your soil was probably too cold for good growth then. They need to be uncovered to be pollinated, so don't keep your beds under cover once you have planted and the plants are blooming. Even with these accommodations, however, we have never gotten peppers before early to mid-August.

but I'll be out of the country for a week in March
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ONE week should not be a problem:

1) Water all your seedlings thoroughly Just before leaving.
2) Put your lighting system on a TIMER.

3) If possible, keep the place slightly cooler than normal.

I got peppers in July this year by switching from OP bells to Carmen, a sweet Italian bullhorn hybrid. I started them inside the second week of March and transplanted outside on May 18. The two in containers were earlier and more productive than the four plants in the ground combined, so I'll likely stick to containers for next year and use the garden space for other crops. Assuming the daytime temps cooperate, I may try to push them still earlier by bringing the containers inside at night. Can't do that with 50 plants, but it's doable with 3-4.

Ultimately it's up to soil temperatures, not air temperatures...but for the most part the root system of peppers aren't "happy" until it's at least in the low/mid-50s regularly for minimum low air temperatures.

Dips in temperatures below that are fine...it's more about the regular temperatures for most days/nights, not occasional blips in temperatures.

That's just a general guideline. You can get them in the ground earlier, especially if the days are warm...but growth is slow until the soil warms up. They really take off when temperatures get into the 60s+ for lows. I get mine in the ground when the nights are still regularly in the high-40s, but that's because it's safe even if the growth is rather slow because we have daytime temperatures in the 60s/70s.

This post was edited by nc-crn on Sat, Dec 14, 13 at 22:55

Getting thing like tomatoes, peppers, eggplants, early in ground in cool air and soil temperatures, without special provisions has NO advantages and often causes stress and delayed growth. If Nothing else, they will not move much.
Provisions to extend your season (in spring) are: Wall O Water, Cold Frame, Hoop, Row Cover, covering soil with black plastic.
Peppers, in particular need warmer temps to take off but they actually do not need real hot weather.
As mentioned, you have to look into prolific types. I am personally in the same situation. I have abandoned growing bells. Instead I plant things like Cubanelle, gypsy, banana, cascabel and some mild peppers with some heat.

In over 40 years of gardening I never had much success with bells--late fruit and then not very many. Then I started to grow Corno di toro, an Italian pepper that, while not bell shaped, tastes like a bell. Seed is available for both red and yellow. Corno di toros are very early and very prolific.