Cold Treatment For Seedlings

MuddyBuckets · January 2, 2020

Cold Treatment is a new concept to me. Will be great if an experienced TV member could walk me through the process for toms and peppers.

1. when to put the seedlings out in the cold and at what temp and duration
2. when to bring them back in under the grow lights and ~68* temperature
3. should this process be done daily and for how many days
4. the plants will be placed outside on the deck when temps are between 40* and 55* in a shaded area or on cloudy days

Any explanation will be appreciated, certainly don't want to damage the seedlings with a bad decision.

SharonRossy · January 2, 2020

I am certainly no expert, but in terms of cold treatment - once the seeds have germinated and are under the lights, it is recommended to keep the temperature on the cool side - for me that means around mid-60’s or a little cooler - with a fan constantly on. Too warm and they will shoot up quickly and get too big before hardening off. Once you start to harden them off by exposing them to some shade and gradual sun, they don’t go back under the lights unless weather conditions don’t allow for leaving them outside. I usually take about a week to ten days to harden off and leaving them overnight. The temperatures are usually around 68 degrees or higher when I start to expose them. But I don’t leave them outside if it’s too cold - 40-55 degrees seems very cold to me. If you put them out at that temperature, chances are they won’t be happy.
More experienced growers can comment on this.

SharonRossy · January 2, 2020

One more point. The first day or so my plants will go back under the lights because they will only be outside for a couple of hours. Then as they slowly stay out longer, I stop the lights.

greenthumbomaha · January 3, 2020

Start your seeds slightly earlier than you would at normal temps. They will grow not only stockier, but a tad slower. When its time to plant out they will grow quickly, so not too much earlier.

- Lisa

slugworth · January 3, 2020

depends on the lights
with the modern led grow lights you can put them directly outside to make more room indoors.
there is no weaning process.

smithmal · January 3, 2020

From what I'm reading, isn't "cold treatment" the same thing as "hardening off?"

MissS · January 3, 2020

Quote:

Originally Posted by smithmal

From what I'm reading, isn't "cold treatment" the same thing as "hardening off?"

No, not at all.

Many people grow their seedlings in 70 degree temps under lights. Here they are saying. Germinate the seed at 70 degrees then turn off the heat. Some even move the seedlings to a unheated porch or coldframe to get the seedlings cool enough so that they are getting the cold treatment. The cold treatment is usually done for 3 weeks or more. Hardening off, is just acclimating the then plants to the sun and wind for 7 - 10 days before planting.

RJGlew · January 3, 2020

I have found that if I grow seedlings in cooler temperatures then their growth rate is reduced and I end up with sturdier, more robust plants. I'm not sure why this is termed a `treatment.' My understanding is professional growers do this to produce the very nice transplants they do. Importantly, I still germinate at 80 F for quick germ to avoid seed rot, use a good seed starting mix to deter damping off, and start them a week earlier so the final transplants are the size I wish.

oakley · January 3, 2020

From the other 'cold treatment' thread...

"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."

Because it is different than 'hardening off'. Coined words exist so it can be spoken among
a group discussing a subject. And not all make sense but we go with it.

If I get the 'soggy flats' someone might finally figure out ..."we call that dampening off".

smithmal · January 3, 2020

Okay, so essentially "cold treatment" is growing your seedlings in a 65-70F environment right?

oakley · January 3, 2020

Yes. exactly. Share information from learning/studying the expert growers and apply to our
small growing situations. It works in 'translation'. Apply the big growers methods and scale it
down to our small scale.

That is what we do in forums...share discoveries and apply it to individual environments and
find what works. My method may not work for others but still worthy to share...

luke · January 3, 2020

This is interesting. I am starting my seeds this weekend in an attempt to catch an early planting date to beat the summer heat.

I plant out in my garage unless I have extreme temps. In the late winter and early spring, the garage ranges from the mid 40's to the 80's. Guess they get some cold treatment by default.

biscuitridge · January 3, 2020

Quote:

Originally Posted by smithmal

Okay, so essentially "cold treatment" is growing your seedlings in a 65-70F environment right?

NO ! Go to other thread on cold treatment, you'll find more exact details. It is not just growing them in a cooler environment!

AKmark · January 4, 2020

Quote:

Originally Posted by RJGlew

I have found that if I grow seedlings in cooler temperatures then their growth rate is reduced and I end up with sturdier, more robust plants. I'm not sure why this is termed a `treatment.' My understanding is professional growers do this to produce the very nice transplants they do. Importantly, I still germinate at 80 F for quick germ to avoid seed rot, use a good seed starting mix to deter damping off, and start them a week earlier so the final transplants are the size I wish.

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

KarenO · January 4, 2020

I see this topic brought up every year and I know many insist it’s necessary . I very much agree with Mark. I’m a gardener, not a plant seller but my method involves starting seeds around the first day of spring in front of a south window and under strong artificial light indoors, moving them to my small greenhouse at potting fertilizing from the start. My aim is for large budding vigorously growing plants for final transplant mid to late May and ripening fruit outdoors by the end of July for some, mid to late August at the very latest or it’s not a variety I will grow again.
Deliberately stunting seedlings makes no sense to me and if it’s necessary to keep them small enough to maintain under Lights indoors they were just planted too soon.
It is detrimental for them to be in an overly hot environment as well but Strong light and air movement produce my best seedlings and early fruit for me.

January 2, 2020	#1
MuddyBuckets Tomatovillian™ Join Date: Sep 2015 Location: Eastern/Coastal NC 8b Posts: 192	Cold Treatment For Seedlings Cold Treatment is a new concept to me. Will be great if an experienced TV member could walk me through the process for toms and peppers. 1. when to put the seedlings out in the cold and at what temp and duration 2. when to bring them back in under the grow lights and ~68* temperature 3. should this process be done daily and for how many days 4. the plants will be placed outside on the deck when temps are between 40* and 55* in a shaded area or on cloudy days Any explanation will be appreciated, certainly don't want to damage the seedlings with a bad decision.

January 2, 2020	#2
SharonRossy Tomatovillian™ Join Date: Jul 2012 Location: Montreal Posts: 1,140	I am certainly no expert, but in terms of cold treatment - once the seeds have germinated and are under the lights, it is recommended to keep the temperature on the cool side - for me that means around mid-60’s or a little cooler - with a fan constantly on. Too warm and they will shoot up quickly and get too big before hardening off. Once you start to harden them off by exposing them to some shade and gradual sun, they don’t go back under the lights unless weather conditions don’t allow for leaving them outside. I usually take about a week to ten days to harden off and leaving them overnight. The temperatures are usually around 68 degrees or higher when I start to expose them. But I don’t leave them outside if it’s too cold - 40-55 degrees seems very cold to me. If you put them out at that temperature, chances are they won’t be happy. More experienced growers can comment on this.

January 3, 2020	#4
greenthumbomaha Tomatovillian™ Join Date: Nov 2011 Location: Omaha Zone 5 Posts: 2,514	Start your seeds slightly earlier than you would at normal temps. They will grow not only stockier, but a tad slower. When its time to plant out they will grow quickly, so not too much earlier. - Lisa

January 3, 2020	#5
slugworth Tomatovillian™ Join Date: Oct 2014 Location: connecticut,usa Posts: 1,150	depends on the lights with the modern led grow lights you can put them directly outside to make more room indoors. there is no weaning process.

January 3, 2020	#6
smithmal Tomatovillian™ Join Date: Nov 2012 Location: Sykesville, MD Posts: 42	From what I'm reading, isn't "cold treatment" the same thing as "hardening off?"

January 3, 2020	#8
RJGlew Tomatovillian™ Join Date: Jul 2013 Location: Alberta, Canada Posts: 643	I have found that if I grow seedlings in cooler temperatures then their growth rate is reduced and I end up with sturdier, more robust plants. I'm not sure why this is termed a `treatment.' My understanding is professional growers do this to produce the very nice transplants they do. Importantly, I still germinate at 80 F for quick germ to avoid seed rot, use a good seed starting mix to deter damping off, and start them a week earlier so the final transplants are the size I wish.

January 3, 2020	#9
oakley Tomatovillian™ Join Date: Jun 2015 Location: NewYork 5a Posts: 2,303	From the other 'cold treatment' thread... "*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.*" Because it is different than 'hardening off'. Coined words exist so it can be spoken among a group discussing a subject. And not all make sense but we go with it. If I get the 'soggy flats' someone might finally figure out ..."we call that dampening off".

January 3, 2020	#12
luke Tomatovillian™ Join Date: May 2011 Location: Mississippi Posts: 177	This is interesting. I am starting my seeds this weekend in an attempt to catch an early planting date to beat the summer heat. I plant out in my garage unless I have extreme temps. In the late winter and early spring, the garage ranges from the mid 40's to the 80's. Guess they get some cold treatment by default.

January 4, 2020	#15
KarenO Tomatovillian™ Join Date: Oct 2012 Location: Vancouver Island Posts: 5,922	I see this topic brought up every year and I know many insist it’s necessary . I very much agree with Mark. I’m a gardener, not a plant seller but my method involves starting seeds around the first day of spring in front of a south window and under strong artificial light indoors, moving them to my small greenhouse at potting fertilizing from the start. My aim is for large budding vigorously growing plants for final transplant mid to late May and ripening fruit outdoors by the end of July for some, mid to late August at the very latest or it’s not a variety I will grow again. Deliberately stunting seedlings makes no sense to me and if it’s necessary to keep them small enough to maintain under Lights indoors they were just planted too soon. It is detrimental for them to be in an overly hot environment as well but Strong light and air movement produce my best seedlings and early fruit for me.