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Duh_Vinci
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Cold Treatment For Seedlings!

I read this post not too long ago by an avid tomato grower, wanted to share with you:

...This was taken out of the book "Greenhouse Tomatoes, Lettuce & Cucumbers" by S.H. Wittwer & S. Honma where they recommend 'Cold

Treatment' for hardening off tomato seedlings.

The cold treatment should be started just as the first true leaves emerge, whether the seedlings are still in seed rows or pricked-off. Air and soil temperatures should be lowered to 52 to 56 deg F for ten days to three weeks. A ten to twelve day cold treatment is adequate during periods of good sunlight. Three weeks are usually necessary in the fall and early winter when most of the days are cloudy and plant growth is slow. The amount of cold during the ten-day to three week period is more important than the time of day in which it is given. Cold exposure during either the day or night, or both, is effective. Night temperatures of 52 to 56 deg F are recommended when the days are sunny and partly cloudy.

Following the cold treatment, night temperatures should be raised to 58 to 62 deg F. Cool daytime temperatures (60 to 62 deg F) should be maintained in cloudy dull weather. On bright sunny or partly cloudy days, temperatures of 65 to 75 deg F accompanied by good ventilation are suggested.

Tomato plants properly exposed to a cold treatment develop large cotyledons and thick stems, with fewer leaves formed before the first flower cluster, up to double the number of flowers in the first, and often the second clusters, and higher early and total yields...
Unknowingly, I was actually giving the seedlings this treatment, since the temperature in my mechanical room, where the seedlings are camping out for now, at night drops down to about 60F (not 56 as suggested, but a dip from 70's under the grow light during the day is a measurable change still). Thickest stems and strongest overall seedlings I've ever had.

Regards,
D

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rainbowgardener
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Interesting, perhaps I'm babying my seedlings too much on the hot pads?

They do come off them and get exposed to cooler temps, because I only run two trays on the heating pads (not willing to keeping upping how much power the seed starting consumes), but this suggests it should happen sooner. I may try it for some (haven't planted tomato seed yet this year), see what happens!

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Duh_Vinci
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I tend to use the heat pad only during the germination stage, then, remove them immediately and straight under the grow light as soon as they emerge.

And while I don't have any "scientific" data for comparison - 2 of the seedlings I kept from the last seed starting mix test are healthiest seedlings I've ever had.

These are seeds saved from my Brandywine Sudduth, seeded on 01/02/2010, most germinated with in 4-7 days, all under the grow light since... 2 weeks ago:

[img]https://drphotography.smugmug.com/Garden/2010-Garden/2010airtray21seedlings/764171675_kXdco-L.jpg[/img]

And these are the two I kept from the batch, as of today (roughly 3 weeks old seedlings)

[img]https://drphotography.smugmug.com/Garden/2010-Garden/2010bwsudduth0203201030daysold/780074604_nwvHp-L.jpg[/img]

[img]https://drphotography.smugmug.com/Garden/2010-Garden/2010bwsudduth0203201030daysold/780074669_HftsE-XL.jpg[/img]

In neeeeeeed of transplanting from these 3oz cups, will do it today.

I believe I'm done experimenting, happy with the seed starting mix, happy with the germination temperature setting and happy with the grow light setup...

Regards,
D

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gixxerific
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I think I might have hurt my tom today. This is the first time I brought my plants upstairs. I was off work so I put them in a sunny widow all day, no clouds. Just went to look at it and it seem a little worse than usual. I planted this in Dec can't remember when I think early. It is cold in my basement with only 1 heat register down there about 10 ft from them, still cold. It was warm to hot where it was sitting today. It never did much probably due to the cold. I have transplanted to a bigger pot and buried everything but the main growth.
Well a picture tall a thousands words right, so here what do you think. It is an Isis Candy Cherry tomato.
[img]https://i272.photobucket.com/albums/jj185/gixxerific/Gardening/DSC03288.jpg[/img]
[img]https://i272.photobucket.com/albums/jj185/gixxerific/Gardening/DSC03290.jpg[/img]

Notice the leaves curling.

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rainbowgardener
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Yeah, looks a little burned. Might have been a rough transition from too cold, to hotter and sunnier than it was used to. Should recover fine though, still basically a nice healthy little plant.

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