It is hard to know how the plants will transition to the outdoors while so young, and here's why:

Had they sprouted outdoors within the last two days, they'd be adapted to outdoor temperatures and light from day one, actually from the very first minute---even before they broke through the surface of the soil. The tiny plants would be barely above the surface of the growing medium and they wouldn't be in a big hurry to get too big too quick because night time low temps would be warning them to take it slow and be careful. They also would be adapting to the strength of the wind from the very second they emerged from above the soil.

Instead, they've been inside in warmer temperatures at night with no wind. So, moving them outside is going to be a risk whether you do it when they're 2 days old or 2 weeks old or two months old. Is it a big risk at this point? Without seeing them and without having a crystal ball to tell us how much wind they'll have for the rest of the week if you move them outside, it is hard to guess.

What would I do? Well, accepting that there are no guarantees, I'd move them to a sheltered porch and see how they respond. I'd try to keep them out of the wind as much as possible. The wind can dry out and burn young plants very quickly. The smaller they are at this point, the better. Understand, though, that if the porch is sheltered enough to keep them safe from windburn and sunburn, they may get leggy and stretch for light on it. However, since you can give them an hour of direct sunlight the first day, two hours the second day, etc., they will be ready for a full day of sun and wind within a week or a week-and-a-half, so the legginess won't get too much worse in just those few days.

If they're already stretching for light and are an inch or two tall, they are more at risk of windburn than if they are still small and a quarter-inch tall. No matter how long a seedling has been indoors, when I move them outside they get one hour of outdoor temps/light the first day, two hours the second day, etc. New leaves are not strong enough to tolerate an abrupt transition. Even if all you have are the cotyledons, they can sunburn or windburn and die and if they do, the plants likely won't recover because the cotyledons are the plants' food supply to keep the plants fed until the true leaves emerge, grow and are conducting their own photosynthesis.

The big advantage in moving them outdoors now is that if they die, you can start a new batch, but if you do not feel like you can keep the plants happy under fluorescent tube lights, then start them outside to begin with. They'll likely be slower to sprout but that's alright because they'll be more likely to survive since they will not sprout in conditions they cannot handle. You will need to cover them up on cold nights.

I don't understand why two day old seedlings under fluorescent lighting would need to go outside so quickly. If you have fluorescent lighting in place for them, the solution isn't to move the plants out into the cold, cruel world at such a young age---it is to move the lights closer to the plants. And, I am assuming the fluorescent lighting of which you speak is not light fixtures in the ceiling. I assume it is a light underneath a kitchen counter or on a light shelf or something. The solution to avoid leggy plants is to move the light down lower or the plants up higher, and to do it ASAP. The lights should be so close to the seedlings that they are almost touching, and I mean almost touching....not that the lights are 3 or 6" above the surface of whatever containers holds the growing medium and the seedlings, but that the lights are 1" or less from the growing medium/seedlings. I keep my lights so close to newly emerged seedlings that it would be hard to slip a toothpick sideways between the two. Indoor lighting is so much weaker than outdoor lighting that it has to be very close to the seedlings. If, for some reason, you cannot move the plants closer to the lights or the lights closer to the plants, then you have little option than to move them outside.

Putting them in a cold frame would protect them from the wind, but not necessarily from the sunlight or heat. You wouldn't take a newborn child away from its mom when it is one or two days old and toss it outside to fend for itself, would you? Remember that tiny seedlings are living beings and to drastically change their environment in a very abrupt manner is not the best thing for them. If you want to grow them in the cold frame, start them there to begin with or move them there the absolute second you see one teeny tiny bit of green emerging from the soil.

For the last few days, I have been carrying out 15 flats of plants from the light shelf (upstairs!) to the outdoors and then back indoors again, doing the standard hardening off of 1 hour the first day, etc. Even with that first day of sunlight being very restricted to just one hour, two tomato plants suffered from mild sunburn. One hour. Granted, two plants from fifteen flats isn't bad, and they are not so sunburned that they won't survive, but it just goes to show that plants that are roughly a month old cannot tolerate too much sun the first day---and generally 1 hour of sun is not too much. For those two plants, for whatever reason, it was too much sun for them and they burned.

The plants are up to 3 hours of sunlight a day now, and today we're going for 4 hours. If the nighttime temps cooperate, I may move them into the unheated greenhouse in a couple of days, but I am watching the nighttime lows very carefully before making that decision. Plants growing inside with a nighttime low of 60-65 degrees will not be happy with an overnight low of 35 degrees. They'll tolerate it, but they won't like it. If the overnight low in the greenhouse dips to 32, then it is likely the plants would die. Clearly I am not going to risk losing 15 flats of seedlings to a cold night at the end of this week. Would I rather not make all those trips up and down the stairs every day? Sure, but I don't want to be careless with young plants and wipe out a month of work.

So, you make your choice as to what you want to do with these very young seedlings and you take your chances. Just remember that wind and sun are the enemy until the plants are used to them, and they can only get used to them with slow, measured, ever-increasing exposure.

And, by the way, a greenhouse is not at all necessary. I have raised seedlings for a couple of decades without a greenhouse! I didn't necessarily want a greenhouse for seed-starting because that requires heating, and it isn't cost effective to heat all that greenhouse's square footage at night when I have room inside for the plants. I wanted the greenhouse more for shelter from the wind because March winds are brutally hard on plants when they are being hardened off. I've lost many more plants to windburn during the hardening-off process than to sunburn because, while it is easy to put the flats of plants on the porch or sun porch out of direct sunlight, it is harder to keep the wind off of them.

Be philosophical about it and figure that you will learn from this experience one way or another. Since your plants are so young, if they do not survive, you've only lost a couple of days of time with this batch. If they do survive, that's great. Still, in the future, I wouldn't start warm-season seeds inside under lights if I couldn't keep them there for a while. If I am going to keep them outside on a porch, cold frame, greenhouse, etc., I'd start them there. That way they are used to the conditions they're going to be expected to grow in.

Good luck,

Dawn

Ah. Okay! I'll have the cold frame ready next year. I guess I'll just run them back and forth babying them.

Thanks!

bon

I agree with Dawn that it would be better to keep them indoors and move them out when they are bigger. But what about experimenting with starting some tomatoes directly in your cold frame. They would be acclimated from the start. And when we get another freezing night, you can either pick them up and move them inside just for the cold time, or if it will only be a light frost, throw a heavy quilt over the closed frame. That gives at least 10 degrees protection for my frames, especially if the frosty night follows a sunny day. You will have to watch that the tomatoes don't get too hot in a frame on a sunny day tho.

If I were you, I'd just buy a light and then you could keep them inside. Those four foot shop lights only cost about 20 bucks. You'll have to find a way to hang the light, but it would be a lot easier and you wouldn't have to worry about putting the plants out into harsh conditions so soon. And the light will come in handy any time you start seeds from now on.

Leslie

CC,

There are many things we take for granted, like the need to put the seedlings very close to the light. I'm hoping that's your problem because it is easily fixed.

If not, here's another line of thought. Are you certain your tube lighting is FLUORESCENT? Here's why I ask. The first year I was in my new home I was so excited about the under cabinet lighting in my kitchen, as I had visions of seedlings everywhere. It was a disaster. It turns out my tube lighting is Xenon, not fluorescent, and it doesn't put out nearly enough lumens, nor in the proper color spectrum. It looks really nice in the kitchen, but it won't grow seedlings.

Seedmama

You're right seedmamma They're not close enough to the light. In addition, I have more seedlings than light. I did manage to get them elevated. Most are within millimeters of the bulb. I'm still attempting to harden them off so I can get them all outside as soon as possible, though.

bon

I just wanted to echo the shop light. The first year I started plants I used this 9 dollar plant light that I got from walmart, took a box, lined it with foil and set the plants down in the box with the plant light placed in holes I put in the sides of the box so I could lower it down on the plants by placing the light thru the holes(the holes were evenly spaced one on each side of the box)(I hope that made sense). It did so good, I almost regretting buying my currently light set up of shelves and shop lights.

CC,

I'm happy to hear. I'm ready to harden off some things this week too, but my ground won't be ready for two more weeks. I'm going to have some intermittent absenses, and my seedlings are more likely to be looked after inside than out, so I'm going to postpone. I'm eager too!

seedmama?

Can you tell me: I'm going to be just, literally, planting beans EVERYWHERE in addition to what we'll be eating to enrich the soil for next year. I don't need trellises if I'm going to harvest, do I? I'll bother with it if it makes a huge difference but... you know. Should I plant anything else, too? Peas? I'm working a smaller section and leaving the rest to be condition for next year. Tx.

CC,
I think it's too early to start beans, especially indoors. It's not warm enough outside. Really, it's on the earlier side of on time for peas, but too early for beans. You should already have your onions in, and be getting ready for potatoes. Dawn has posted the link to the OSU recommended planting dates. It's too hard to navigate from my phone to post a link but when I'm back at my desk i'll see what I can do.
Whether or not you need to trellis is determined by whether you are growing pole beans or bush beans.

No, that's okay. I still have a link and a copy of the dates. I was pondering the cover crops and whether I should trellis them or just let them lay. If I let them lay they might be more prone to get sick and will not penetrate the earth as well with their roots (especially for sunflowers). I have some clay in my garden that must be contended with. Fortunately, it's highly organic and nutrient rich so the plants do like it. They just can't get the drainage they need.