what's too much sun for tomato seedlings

A couple days ago I made the mistake of putting my tomato seedlings out on a windowsill for direct sunlight, and a few hours later I discovered they were all withered. (We've had a lot of sunlight here lately in Portland, Oregon.)
I immediately removed them, and enclosed them in a humidity-containing package (it used to be a doughnut package but I filled it up halfway with potting soil), and hid it away.
The next day, 10% of the seedlings began to perk up again.
If I buy a photometer, how much light should tomato seedlings be exposed to?
Is the real problem loss of water instead of too much sunlight?
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I'd speculate that it's not too much light, but too much heat. Did they get dry while in the sunlight? Thomas

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Thomas wrote: |I'd speculate that it's not too much light, but too much heat. Did |they get dry while in the sunlight?
Yes, they dried up. The seedlings were about 2 inches tall but they all fell over and withered up. After I returned them to the dark, and controlled their humidity, 10 percent of them perked up again.
I think I ought to buy a photometer.
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Matthew Montchalin wrote:

My tomatoes were started from seed in a 5-gallon bucket. They were then placed next to the patio door (south window) and allowed to grow. There's probably about 2 feet of space between the window and the plants. The more sun they get, the taller they grow. The more water they get the more they grow. I'm looking for tomatoes sometime in March.
I don't think you can have too much light for plants, but that could be an interesting experiment.
Oh and don't rule the other tomatoes out yet. They may come back "from the dead." Last year we had about 18 do that. (That was supposed to be the whole planting too. We replaced them and up come the original plants. They were a little better established, though.)
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Seedlings should be gradually exposed to direct sunlight, which means initially keeping them off windowsills unless you can construct something to filter the light.
Seems a little early for starting tomato plants. How early in the Portland/s growing season does the overnight temperature stay above 55F?
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il Fri, 18 Feb 2005 15:11:45 -0800, Matthew Montchalin ha scritto:

It can be too much sunlight and its pal heat. If you think about how seedlings start in the wild, they are protected by the bigger plants and have quite a sheltered upbringing. Seedlings are more fragile than a full grown plant and have less resistance to bad growing conditons. The thing with windows is that they get incredibly hot. You want a themometer, not a photometer, if anything. I protect them with shade cloth or lacey curtains when on my windows, but even then I watch the temperature as all morning in window light can be too much for seedlings. At night they rested near the fridge cooler which helped keep them warm on cold spring nights.
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On Fri, 18 Feb 2005 15:11:45 -0800, Matthew Montchalin

You probably shocked your plants with the sudden bright light. Seedlings need time to acclimate to bright sun. Try them for just an hour a day, doubling the time each day. And make sure they are getting enough water and food. I can't imagine plants getting too much sun, as long as they are gradually acclimated. Considering your location, you have plenty of time to start over again, a few times. Sow them in your humidity container and as soon as the very first bit of green appears, get them out of the humidity and into the light. Your bright window should be fine if done this way. Flourescent tubes an inch above the plants would do as well. No acclimatation needed. The humidity beyond this point is asking for fungus / damping off / weakening. conditions. And you don't need a photo meter, unless you are a very serious photographer.
-- Mr Gardener -- Zone 5 - On The Maine Coast
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Mr Gardener wrote: |>A couple days ago I made the mistake of putting my tomato seedlings out |>on a windowsill for direct sunlight, and a few hours later I discovered |>they were all withered. (We've had a lot of sunlight here lately in |>Portland, Oregon.)|> |>I immediately removed them, and enclosed them in a humidity-containing |>package (it used to be a doughnut package but I filled it up halfway |>with potting soil), and hid it away.|> |>The next day, 10% of the seedlings began to perk up again.|> |>If I buy a photometer, how much light should tomato seedlings be exposed|>to? |> |>Is the real problem loss of water instead of too much sunlight?| |You probably shocked your plants with the sudden bright light.
Well, yes, probably.
|Seedlings need time to acclimate to bright sun.
Are there any breeds of tomato that are less shockable than Beefsteak or Roma?
|Try them for just an hour a day, doubling the time each day. And make |sure they are getting enough water and food.
I was hoping that the tomatoes would thrive on potting soil and high humidity.
|I can't imagine plants getting too much sun, as long as they are |gradually acclimated. Considering your location, you have plenty of time |to start over again, a few times.
Yes.
|Sow them in your humidity container and as soon as the very first bit of |green appears, get them out of the humidity and into the light. Your |bright window should be fine if done this way. Flourescent tubes an inch |above the plants would do as well.
I have theory that Cool White fluorescent lights will work just as fine as Grow Lights.
|No acclimatation needed. The humidity beyond this point is asking for |fungus / damping off / weakening.
Argh! I was hoping the terrarium would be self-sufficient, and I could just seal them off from the outside world.
|conditions. |And you don't need a photo meter, unless you are a very serious |photographer.
If I knew the amount of light that was appropriate, I could computerize the setup.
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On Sun, 20 Feb 2005 12:32:57 -0800, Matthew Montchalin

No. Seeds are seeds, when it comes to sudden changes. No different, really, than you or I spending too much time in the bright sunlight after a winter of covering up indoors.

"Potting soil" is usually too heavy for optimum seedstarting. Try a soilless mix specifically labeled for starting seeds. This mix is usually a combination of vermiculate and peat and maybe a little lime. ProMix is a popular brand, another is Jiffy Mix. If neither is available, plain vermiculite will be fine. These mixes contain no nutrients, your seeds contain all the food they need to get them started through the "seed leaf" phase. After that, water with a half strength fertilizer solution. I use fish emulsion and/or liquid seaweed. Shultz's famous 7 drops per litre all around plant food works just as well. Maybe better.
Humidity covers are used to keep the seedbed moist, water being one of the requirements for germination. After the seed has germinated, it gets its water through its roots. If you think about a plant in nature, its stems and leaves are above ground, high and dry in the fresh air.

Yes. Not just a theory. Cool whites, the $1.99 cheapies, contain the parts of the color spectrum that plants need to make leaves. Since you are not attempting to produce flowers or fruits under lights, grow lights are mostly superfluous. I've used both, but I will never be 1000% convinced, so I often use one cool and one grow in each of my 4 foot shoplights. Just in case I don't know what I'm talking about. By the way, I've noticed in recent years that more and more suppliers are selling "energy saving" 4 foot flourescent tubes. On close inpection, you will discover that these bulbs are only 32 watts, rather than the common 40 watters we have been usiing since time began. Buyer beware.

Yes, and I'm sure that's how the big producers do it. But without the greenhouse and the specialized equipment, we must do a little hands on care in order to get our seeds ready for the garden. You have reminded me of the first year I started my own seeds, a few decades ago. I had an elaborate setup using large aquariums with covers and bright lights, all under a tent made of 4 mil poly, the entire affair about 6 feet from the woodstove to ensure plenty of warmth . . . what a disaster! I learned my lessons about heat and humidity in that one fateful spring - a truly humbling experience.
-- Mr Gardener -- Zone 5 - On The Maine Coast
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Matthew Montchalin wrote:

those seedlings died because of dryness and heat, not too much light. better start over, and keep them moist at all times.
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On Fri, 18 Feb 2005 15:11:45 -0800, Matthew Montchalin
Hay folks! too many complex answers to a simple problem (I think).
Think about this. If your first day at the beach you rippedoff your shirt and stayed in the sun all day- - -You'd wilt too! BUT, if you started out at say 15 minutes the first day,,30the next and etc, you'd soon adapt to it.
Now for the person that mentioned using florescent lights instead of grow light. It works great! BUT, you need both the Soft White and Daylight type bulbs(different light spectrums ).
I raised tomatoes in my basement (hydroponically ) and had tomatoes in January and February one year. (lots of work).
Another thing you can do by using lights is; Adjust your day length to make your plants think it is summer. Don't over do it though. Plants manufacture food during the day and grow in darkness (I know there are exceptions). bit as a general rule.
Guess I might have offended some, but not my intentions, After 70+years of watching thing grow, I still get a thrill out of it..
All of you gardeners have a good day- -Rogerx

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