Supplemental lighting is needed 1" above the plants. Check out all the FAQs (there is one on leggy seedlings and lighting) and info on this question posted over on the Growing from Seed forum here. Dave Here is a link that might be useful: Growing from Seed forum

I just stuck a few of my hardier plants out about two weeks ago, and after a few nights in the 40's when I brought them in, I just left things to sit out there. My vanilla got a little burnt, despite being in the shade. I think that's because it gets so little light during the winter for a plant its size. I've been growing it on a trellis, patiently looping it as it grows. I'm going to have to get a greenhouse if I ever want to see it flower. Anyway, I'm really excited about summering outdoors. I've only tried a few plants at a time over the years, but this year, I had my husband build me a proper table for them, so I'm taking everyone out. I've had some bloom that hadn't bloomed for years (not even when I bought them) suddenly reward me with huge spikes, so I'm geeked to give them all a shot of real sunshine!

Tony, The way I figure it, you were originally asking about putting a heater in your plastic thing because you were possibly interested in replicating a greenhouse. The winter sowing people generally use methods that roughly replicate a coldframe (but with the improvement of letting some precipitation cycle through). Coldframes and such are awesome for starting things that need stratification, which I don't think applies to any of the seeds you listed (not sure about the rockwort offhand). And there's nothing wrong with using them for other stuff either--snapdragons, for one, like it cool. On the other hand, heated greenhouses and indoor light setups can give you more of a jump on many things, which may be a benefit when you're sowing many annuals and more tender things. I'm sort of sorry you didn't try out your experiment. I would have been curious to hear how it worked. Some people from the winter sowing forum like to use their method exclusively. I think that in cold places like our state of Illinois, indoor lights and warm greenhouse environments are great tools. I do agree, however, that much of what you're sowing will be fine with either method, though I'm not sure I'd want zinnia seeds experiencing below-freezing soil temps. In case you're still considering it, I'd be a little nervous about the space heater idea just for fire/safety reasons--those tented shelving units have been known to blow over--but I think it's a worthy experiment if you have the time and proximity to keep an eye on it.

highalttransplant, I thought about doing that, but since many of my tom seeds came from trades (and there's NO info on most of them... rare seeds apparently) I have no way of knowing the DTM. I can safely assume that most IND beefsteaks have higher DTM so I'll keep those babies inside with me. How readily do tom seeds rot when they've been winter sown? I'm a little concerned because of our weather as of late. It will get warm for a few days then a hard frost hits for multiple night in a row. And what about other veggie seeds? What is safe to wintersow without a high likelihood of losing the seed to rot? Thanks! Abby