Giving Seedlings the Cold Treatment

[bower]

I'm sure everyone's methods are a little different, but personally I take the seedlings from the heat mat as soon as the cotyledons are free of the seed, and I put them in cell pack with a tiny pinch of bone meal to ensure that the necessary nutrients are available.
I don't have temperature control really other than moving seedlings to a warmer area, so they probably (or surely) get more cold exposure than the average deliberately 'cold treated' plants. One thing about the cold is that moisture requirements are much less. So I water the seedlings infrequently and only when they are visibly dry. This is potentially a problem with the liquid fertilizer regime,because I don't want to flood my seedlings or leave them in wet soil when they're too cold to take it up. I used promix last year and really didn't like it, it got very soggy and stayed wet too long after watering for my liking. I will be switching back to a mix of peat and compost, where I don't need any ferts other than the pinch of bone meal.
The other advantage of dry ferts for me is that all the seedlings get the same amount, where my watering tends to be uneven - I'd be lying if I said I could water them evenly, and I'm not set up to do bottom watering especially with the concern about overwatering in cold conditions. All my seedlings have excellent roots, so the bone meal method works for me.

[greenthumbomaha]

Great tip. I have bone meal on hand. Thank you for sharing.

- Lisa

[aimeehoward]

I had no idea about that method and how effective it is. Thank you for sharing.

[chalstonsc]

My pleasure, enjoy

[Ricky Shaw]

An excellent thread here on cold treatment, well worth the time to read it all. I had cold treated some of my seedling last year and felt those plants on average took off better and set more early fruit.

I don't start seedlings for outdoors till April, but have been testing seed and media this month and thought I'd share a some before and after pics of 2wks of cold treatment. This might help some in estimating how much earlier they may need to start if cold treating.

These are Crnkovic Yugoslavian seedling packs separated at the first emergence of true leaves Jan7 and today Jan21, all T5 lighting.



(left) cold treatmented: 12/12 light, ~57F days , ~50F nights

(right) traditional seedlings: ~75F and 24/7 lights week1 and 18/6 week2

[chalstonsc]

SWEET....

[Ricky Shaw]

Couple of weeks later with all plants on 16hrs of light and the cold treated Crnkovic's (right) have caught up to their siblings. (left 3 plants)

I'm not really seeing any need to start cold treated plants any earlier and the 5 week mark is about right for starting my seedlings whether cold treating or not.

[bower]

They look great, Ricky.
I missed the cold treatment last year and I regretted it...

[chalstonsc]

Bower,

Good to hear from you again

I'm missing my cold treatment routine this year, and so it goes....

Maybe I'm not too late per most recent post?

Tom

[bower]

Originally Posted by chalstonsc

Bower,

Good to hear from you again

I'm missing my cold treatment routine this year, and so it goes....

Maybe I'm not too late per most recent post?

Tom

Hey Tom, I think it's still worthwhile at any stage of seedlings. I usually put them right into the cold as soon as they've sprouted, but if I couldn't do that, I would still try and cool it down a bit later on.

I know the regimen that Ami described is different from what I've done, and maybe not as cold either, nor as prolonged. But last year I started my seedlings upstairs in a warmer room (closer to 70 F or at least 65F most of the time) and let them enjoy all the heat in the south windows as well when the sun came out. They definitely got too leggy before it was time to plant, and they had more cold stress when I did put them out. The usual cold room, temperature in that window at night would be closer to 50 F - which is as good as they get after transplant here anyhow!
How big are your seedlings, and what do you usually do with them?

[murihikukid]

Hi...Is the thread still active as I have a couple of questions i would like to ask ...Thanks Ron New Zealand

[amideutch]

Ask away Ron.

Ami

[geoffrey44]

So far as I am aware this thread is still a goer.
Have been using the cold treatment for several years now ( earlier postings ).. for both maters and peppers.
This method certainly works for me but I would also mention that it took quite a while for me to get an optimum fertilisation routine sorted out... bit of fine tuning required there.But ,for me , the bit of extra attention required gives wonderful results
Geoff

[murihikukid]

Originally Posted by amideutch

Ask away Ron.

Ami

Hi..First its so good to hear from you.....Now last season I asked why I could not grow seedlings like the growers and i was told its because of the "cold treatment" but later i got mixed up between Hardening off and cold treatment ..anyway I was searching Google one day i came across a web page of a UK company that makes growth chambers...I can get the website later if interested and i thought "Hell I could make something like that" ....So with the help of an electrical friend I made up a chamber that is just an old stainless steel freezer with rails in it for seed trays to sit on and two radiators with two computer fans on each to blow the cold air through and around and under my trays ...

...a lower/raise lid with 10 x 150cm LED tubes and 6 fancy computer fans (3 at each end ..2 red and 1 blue) with 33 Led's in each.....this was to blow air over the seedlings when the lid was lowered ... this enables me to give as many hours of light daily as required..
My electrical friend was busy making up a cooling unit with a submercible water pump...the idea being to pump cool /cold water from the reservoir in the cooling unit through water tubes into the radiators in the "growth Chamber " and back out to the reservoir in a continuous flow...to cool the air in the growth chamber...
Well we got it going but I soon realised we were not going to reach our objective of nearly 10 degrees so I had an old fridge freezer and I first put the reservoir in the fridge compartment then the Thermostat failed so the reservoir next went into the freezer compartment and I put it under control of an electronic Thermostat (STC-1000) with the probe in the air with the growth chamber and things were looking good until just 12 hours after the trays of my seedlings (with underneath watering) were put in the chamber...the lid with the lights were lowered to as close to the top of my seedlings as I could ..all fans were on ...the thermostat on the freezer was set to switch it off when the air in the chamber reached 10.2 degrees and come on again @ 10.8 degrees... and we were nearly there and something happened... I saw the temperature rising and initially i thought it was the lights creating problems which they were but it soon became evident that the freezer had completely failed....So I let everything carry on for a few hours but the temperature kept rising and i switched off the lights ,raised the lid....kept the fans going ...and thats basicly where I am at now.....

However not to give up.. I have two freezers and I have learnt more in the last 12 hours about refrigeration than in 74 years of life.....I now know that as far as i can tell both compressors are OK...The start Relay on one is OK but I think the transformer feeding the power has failed while on the other I think it is the start relay so hopefully both can be fixed reasonably quickly and cheaply while I am also now looking for another freezer for backup just in case to get the water temperature right down to off set the heat coming from the LEDs....and hoping that my seeds won't mind the hiccup??

Now people think I am crazy but I don't think so....All I am trying to do is grow my seedlings in an artificial climate..giving them the temperature and daily light pattern that experts say they should have....Down here in the a**se of the world weather patterns can be all over the place.....and although I have an excellent greenhouse I think that ensuring the seedlings are grown properly is the secret to healthy plants later on......Within three to four weeks all should be out in my greenhouse ...
I have some photos but its 2.23am here and its cold.. so I better get some sleep ...Regards Ron

[MuddyBuckets]

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.