Cold Treatment For Seedlings

[oakley]

AK and Karen are two of the best successful and respected growers on this forum .

Information is to be absorbed and possibly used if you have had issues in the past and want to experiment a bit.
No method is an absolute. We all have different climates and humidity concerns.

My grow room is perfection until the snow melts and outdoor temps rise. (humidity!)
Still cooler temps indoors but humidity is a battle.
My early starts are always my best seedlings. Strong enough to handle minor humidity
issues. Late starts need and upstairs dryer bedroom office.

[sjamesNorway]

Cold Treatment

- subject the seedlings to a cold treatment:
from Growing greenhouse tomatoes in soil and in soilless media Dr. A.P. Papadopoulos Research Centre Harrow, Ontario
Under a cold treatment regimen, place young tomato seedlings in a day and night air temperature of 50-55F/10-13C for approximately 2 weeks, while providing as much light as possible for 9-12 hours. Seedlings should be subjected to cold treatment just after the seed leaves (cotyledons) unfold and the first true leaves start to appear (see below). Shoots kept at low temperatures at this stage of growth produce a small number of leaves below the first flower cluster and therefore flower earlier; roots kept at low temperatures cause branched clusters, i.e., many flowers in the first and possibly the second cluster. Cold temperatures during both day and night are effective.

The cold treatment increases the number of flowers but does not influence the setting of fruit. If later conditions for fruit setting are right, a greater number of flowers will set fruit because of the increased number of blossoms. If, however, the temperature for fruit set remains less than ideal, the pollen does not germinate and grow normally, resulting in poor fruit set and cat-faced fruit. When the cold treatment is used, seed 10-14 days earlier than usual to compensate for the slow growth rate during the cold treatment. The growth medium in the seedling trays must be sterile, because when plants are grown at relatively low temperature the danger of damping-off is increased.


Terminate the cold treatment when the second set of true leaves starts to appear.

Tip 2
- As the plants grow, shake them some or drag a stick gently accross the tops of the plants. The plants will react by producing sturdier stems that are less brittle and be a little more resistant to problems like pith necrosis.
Leggy plants can result from poor light, excessive watering, high nitrogen, warm temps or combinations of them. Cooler temperatures can slow plant growth down as well as cutting back on water and fertilizer. Light can be supplemented with flourescent shop lamps. If the plants are leggy when you plant thats, okay, just carefully bury the stem into the soil and roots will form along it.



I've used the cold treatment for three or four years. It works very well for me.



Steve

[PNW_D]

duplicate post

[RJGlew]

Originally Posted by AKmark

I live in AK, and I am not sure about any of this. I sell plants in the Spring at our nursery. To get stocky robust seedlings and starts we give them light, and food formulated for tomatoes. A fan may help too. I think stunting plants will just hurt growth rates, and we have a short season here for many.

I see no value, I do think feeding plants better at seedling stages may be a better approach.
Mark

Hey Mark, which fertilizer, and application regiment do you use?

[AKmark]

Originally Posted by RJGlew

Hey Mark, which fertilizer, and application regiment do you use?

We use 4-18-38. You have to use Calcium Nitrate and Magnesium Sulfate too. For starts we are about at 1200 PPM for the mix. It's three parts. (Now they do have hobby blends that are two parts). Use it every time you water.

We sell plants starts and do produce for farmers markets, so we have economic thresholds that must be addressed. Presentation of plant starts quality, and production of fruit is what we do.

We have a huge support network, we do not make this stuff up. Now there are other fertilizers that work just as good, maybe even better. We send leaf samples to labs, they send us back element numbers on bar charts that read from poor to optimum.

It is science. What we do is pass along info from the labs, that is all. Figuring out this stuff is way beyond me, but I am a good listener.

When your root zone is cold your plants turn purple. This is an issue with the uptake of P because of the cold. Ratios are also affected. Now we can quickly turn this around, obviously, but why do this to begin with? I firmly believe, if your starts are spot on out of the gate they will take off faster, and that all adds up to vigor, health, disease resistance, etc, etc. As you can see I set starts on tables to keep them warmer. These are just various stages that will go up retail at some point.

On a real good note, chilling your starts is not going to result in poor plants. We are always just looking at the best methods, the rest have no value to me.

Right on, Happy New Year.

[RJGlew]

Originally Posted by AKmark

We are always just looking at the best methods, the rest have no value to me.

Right on, Happy New Year.

Thank you for taking the time to write this out & for providing the motivational picture. After reading this I'll see what improved fertilization does for me this season, since historically I have simply gone with 25% strength 20-20-20 one time per week. Calcium nitrate is basically 15.5-0-0, so can I assume you are using it in combination with the 4-18-38? Interested in the 1200 PPM figure - everything I read suggests that a PPM is recommended to growers for nitrogen, then the PPM of the phosphate and potash simply falls out from the fertilizer mix. So in your context, what does the 1200 PPM actually refer to? Is that your desired injector concentration? Epsom salts too - interesting - do you have magnesium and/or sulfur deficiencies, or is it a preventative measure? Best regards, rg.

[AKmark]

Originally Posted by RJGlew

Thank you for taking the time to write this out & for providing the motivational picture. After reading this I'll see what improved fertilization does for me this season, since historically I have simply gone with 25% strength 20-20-20 one time per week. Calcium nitrate is basically 15.5-0-0, so can I assume you are using it in combination with the 4-18-38? Interested in the 1200 PPM figure - everything I read suggests that a PPM is recommended to growers for nitrogen, then the PPM of the phosphate and potash simply falls out from the fertilizer mix. So in your context, what does the 1200 PPM actually refer to? Is that your desired injector concentration? Epsom salts too - interesting - do you have magnesium and/or sulfur deficiencies, or is it a preventative measure? Best regards, rg.

No, not PPM Nitrogen. That make some super green then super brown plants. LOL We do use some fertilizers like that, but they also break it down for us and include all elements. That number is read from a standard TDS meter, it comes right from the manufacturers.. It measures dissolved solids. Your conversion factor is 700, not 500 with the meter.

If you don't use Ca and Mg like they recommend your plants will die. Remember we are talking containers, small starts. When you get to your soil in the garden you will want to go back to your growing techniques or water this stuff down.

I prefer EC/ Electrical Conductivity. Most meters have both measurements which measure a charge put off by fertilizers. for seedlings it is something like 1.6-1.8, mature plants, 2.0-2.28.

Try Blue Lab. This is much easier than you think.

[RJGlew]

This is much easier than you think.

Thanks again - this is really good information, and certainly gives me what I need to begin to do some reading. This area seems like it will be quite interesting to learn about. I'll follow your suggestion & look at Blue Lab. Regards, rg.

[smithmal]

Is cold treatment an effective seedling growth treatment for just tomatoes, or does it also benefit other veggie plants? I ask because I germinate and grow most of my summer veggies at the same time. I unfortunately don't have room (or money) to create two separate growing rooms/environments.

[amideutch]

Hey Mark,

Check out the book "Greenhouse Tomatoes, Lettuce & Cucumbers by S.h. Wittwer & S.Honma

ISBN 0-87013-210-5. They work out of the Michigan State Agricultural experimental Station. They are the ones who developed the cold treatment for tomato seedlings among other things including the use of CO2 , fertilizer rates you name it.

Ami

[AKmark]

Originally Posted by amideutch

Hey Mark,

Check out the book "Greenhouse Tomatoes, Lettuce & Cucumbers by S.h. Wittwer & S.Honma

ISBN 0-87013-210-5. They work out of the Michigan State Agricultural experimental Station. They are the ones who developed the cold treatment for tomato seedlings among other things including the use of CO2 , fertilizer rates you name it.

Ami

Thanks I will take a look. I am just reporting from observation, and do live at the 62nd. I am always up to learn something new though. I don't know any farmers up here who do this practice, not that there aren't some.