Giving Seedlings the Cold Treatment

[mdvpc]

I used a botanicare microgarden this fall.

I started my seed with bottom heat. As soon as they germinated I just placed them on the hydration clay pebbles where there was room (there was lettuce in a rockwool cube growing in each of the containers). There is a grow light on 12 hours a day.

The hydro system is a flood and drain, so it pumped the fert solution up onto the clay pebbles 3 times a day.

Its cool in there-the water temp is 60 degrees. I had very good results with this. Short, stocky plants. When I was ready to put them in the greenhouse, they took off. I will post photos of my bush goliath and al-kuffa that I just put out in the greenhouse a few days ago.

[mdvpc]

Here are the photos-the first is Al-Kuffa that has been planted out about 14 days, the second is Bush Goliath that was put out 5 days ago

[amideutch]

Michael, nice looking plants! What is the aggregate in the grow bags? Ami

[mdvpc]

Ami

Coir. There is some pelleted compost and biosol on top of the medium-about a 1/2 tablespoon of each.

[snappybob]

@DarJones Should this wet dry cycle of watering start as soon as the plant emerges from the soil or is there some point at which it is best to start this watering regimen? Such as first set of true leave? Second set? I would be afraid to let my tiny seedlings get too close to wilting for fear of losing them altogether.

[Garf]

I had to place some seedlings on a rack against the garage wall for lack of room. They only get 6 hours of sun a day then diffused light till sundown. The seedlings are the healthiest I have. This is with temps dipping near freezing at night. Amazing.

[maricybele]

Excellent post, this post explains why my tomatoes did better in the garage then in the house. The garage is cooler and the plants were more robust, and grew slower and had thicker stems. The ones inside the house were not as robust.

[Garf]

I think the heat radiated from the garage prevented freezing at night.

[erlyberd]

Sound familar guys??? We know all to much about the cold treatment!!!!LOL

[lrsasso]

Thanks.

You say I used the wrong forum. Which is the correct one?

Regards

Lou

[sjamesNorway]

Originally Posted by Fusion_power

Study carefully before you do this. It is dangerous if you don't watch carefully and know what to do.

The "big boys" do tomato plants by growing them in huge greenhouses that never get below about 70 degrees. A tomato plant can be forced to salable size in 5 weeks at this temp and that is exactly what the "big boys" want. Unfortunately, these plants have never been stressed and when you set them out in the garden, they sulk for 2 or 3 weeks before deciding to grow.

Folks like me who grow up to 50,000 plants a year usually are a bit more in touch with their plants. I grow in a greenhouse and I definitely use the cold treatment methods when feasible. There are a few gotchas that you must know how to avoid. The first is that low temps significantly slow down plant growth. Allow an extra week or two for cold treated seedlings to grow. The second is that tomato seedlings are VERY sensitive to excess water. What's excess? You must let tomato plants dry out until they just start to wilt if you want them to be healthy. Give them plenty of water when they are dry, just be sure they are thoroughly dry before you water. The last caution is that you need air circulation even when it is cold. Be sure you have a fan blowing across the seedlings at least part of the day. It encourages the plant to grow a sturdy stem.

Does it work?

I can assure you that cold treatment of tomatoes is VERY effective. It shortens time to first flower truss and boosts overall production.

DarJones

Hi DarJones, A thousand thanks (Norwegians say, translated) for the watering tip. I've been giving my seedlings the cold treatment for a week, and I'm using a fan, BUT I've been bottom-watering when the "soil" gets dry on the top. You've probably saved me from ruining them.

Steve

[Jeanus]

Amideutch would you mind if I posted this in another gardening board. The reason I am asking here is it bumps it up on TV too and it is easier for me to find it. I am definitely going to start my plants this way next year. Question Do you do the same with peppers and egg plant?
Thank you Jean

[amideutch]

Amideutch would you mind if I posted this in another gardening board. The reason I am asking here is it bumps it up on TV too and it is easier for me to find it. I am definitely going to start my plants this way next year. Question Do you do the same with peppers and egg plant?
Thank you Jean

Go for it! As far as egg plants and peppers I can't say.

Ami

[geoffrey44]

Thought this might be of interest.
These two have been grown under lights in my garage which receives no heat.The temperatures have not exceeded 55f in the last four to six weeks and most of the time have been around 45 to 50f..I am growing a range of tomatoes and even the chillies are progessing very well.The plants certainly have nice thick stems and are quite robust with really good colour. They are going to have to continue in this environment for another 4 weeks or so then I will start to plant some of them out but cover from the winter weather will be in vogue.

[sjamesNorway]

Originally Posted by amideutch

Ever wondered how commercial seedling providers get these beautiful, stalky, plants with thick stems to market? It's called the cold treatment and has been going on at commercial greenhouses for over 30 years. Here's how they do it.

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.

Basically this cold treatment is used to give healthier, more stalky seedlings that will give increased yields and earlier harvests. In regards to light intensity and duration they had this to say.
The tomato is a facultative short day plant which flowers and fruits earliest if the day is not extended beyond 12 hours by artificial light. Young tomato plants do not need the light intensities of full sunlight. Where there is no overlapping of leaves, light saturation is reached at intensities from 2000 to 3000 foot candles, or about one-fifth to one-third the intensity of direct sunlight at high noon. If artificial lights are used, an intensity of at least 500 foot candles should be provided at the leaf surface. Tests with fluorescent fixtures reveal that Wide Spectrum Gro Lux is slightly superior to cool white.
Hope this helps. Ami

Hi Amideutch. I want to thank you again for recommending the cold treatment this spring. My seedlings turned out to be nice and sturdy, and are growing well after being planted out.

I'm wondering if you, or anyone else, has experienced (as I have) that quite a few of the plants which have received the cold treatment have megablooms as the first blossoms?

Steve