early cold treatment, anyone?

[johno]

Tomato growers: How many of you do an early cold treatment of your seedlings? I have meant to try this for the past few years. This year I finally remembered about it early enough to try it. It says you need to start them 10 - 14 days earlier if you do this. See Tip number 1:

http://www.kdcomm.net/~tomato/Tomato/start.html

Tip 1 - 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.

stages in seedling growth used for initiating (plant A) and terminating (plant B) the cold treatments
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.

[janezee]

Thanks for that info. It's just what I want to do. Tomato seeds, here I come!

[amideutch]

johno thanks for bringing the cold treatment up as it is that time to start preparing. Ami

http://www.tomatoville.com/showthread.php?t=13171

[bower]

I read the thread that Ami linked, so I'm trying to do it, but don't have perfect temperature control. I have 3 varieties started early, and in the stage shown in your graphic: they're under lights in a NW facing window for ~ 12 hours a day, in an unheated corner of the basement. It's not quite as cold as it should be I think, although I turned down the basement thermostat to get closer (brrr!).

Hoping for an early spring.

[Randall]

I'm a fan of cold treatment (possibly a sucker for abuse but that's another topic)! Here's a shot of a plant that's been under 2 1/2 wks worth or so. It makes them really stout and purple:

[huntoften]

I do it every year...this year is tougher though with the record high temps we've had though. I end up with shorter, stockier plants, but they have amazing root systems and perform VERY well when transplanted.

I've had a lot of customers use my plants and were amazed at the health and early production of varieties they've gotten from me when compared to "hot house" plants they've grown in the past.

[bower]

Well, it was definitely cold enough for my february seedlings to be stocky and purple!

The tricky part now seems to be, whether the greenhouse is any better than that cold window.

I put my early plants out there, after I realized it wasn't dropping to freezing any more.. but it's still a bit colder than the window. I picked up a thermometer at the dollarama last week, and verified the windowsill temp is 60F or less, while the greenhouse temp is 38-42F at night, going to 50 or 60F on a day the sun doesn't shine. When the sun shines, look out!.. it was over 80F air temperature in the shade. Quickly dropping to 60F in the evening and as low as 38 overnight again.
The plants that endure these extremes... they are truly golden.
It's true... I would sacrifice innocent seedlings for the chance at an early tomato!

[Randall]

I tried cold treatment last year with 10 out of 40 plants. There was certainly a very noticable increase in flowering and yield on those 10 plants. The very same varieties from the same seed that did not undergo cold treatment didn't yield nearly as well. It made me a believer. This year they are all getting the cold treatment!

[Tracydr]

Mine get planted when temps are in the high forties to low fifties at night. Before that, I've kept them outside at least a month, maybe six weeks or more, except nights where temps are supposed to be less than forty five.
Days are pretty warm but chilly nights. To begin with, I keep them close to the house but then move the cart out on the pool deck with much less heat mass and protection.
I noticed last year my home grown seedlings, which were much smaller than the few I purchased, caught up to purchased and set very, very heavily on first and second truss. Some cat facing due to cooler nighttime temps early on but we have to race the heat in AZ.
I think there is something to the cool treatment, although for me it's simply my way to harden off and keep from having to lug all those plants in and out every night.

[chalstonsc]

Cold treatment works very well for me ....highly recommend...and in my experience does not have to be exact to the article above....best you can do will be better than not doing at all..by far

[JamesL]

Great info here y'all, thanks. Doing this for the 1st time this year as well.
Plants have been "chillin" in my garage for 2 weeks. Looking nice and purply.
The picture is from last week, I just potted them up over the weekend and gave them the Actinovate and Myco treatment.

Question - Hardening off - How important will this be when it comes time to put them out for the season? Not worried about the temperature, but with respect to direct sunlight. Do they still need to be eased into it a few hours a day?
Thanks.

[ljp]

Mine are getting cold treatment -- down to 35F in the greenhouse last night. I have supplemental heat but I expect the best I can do is 2-3 F degrees above freezing. The 600 litres of water is what really keeps the temperatures above freezing. I'm expecting the tomatoes will get these lows two or three times a week for the next month and a half.

[kath]

James-

Definitely take it slow. It helps if you are around during the day to monitor. If it's windy, that will be a factor is well- maybe you can rig up some wind protection. I once rigged up a wind protection system that also allowed shadecloth and later fine row cover to go over the top and they were able to stay out all day right from the start. Starting out in dappled shade is a possibility or just limiting the sunlight for an hour or less at first, starting on a mostly cloudy day, etc. all can help in the beginning. I start putting them out as tiny babies if the temps are in the 50's and bring them back under the lights for a while at night and they hardly need any special treatment when they're ready for plant out. Just experiment depending on your situation and supplies- the plants will start to look wilty when they've had too much for the day. You really don't have to wait to harden off right before plant out- I think they grow faster when they have some real sun during the day. Hope this helps. kath

[JamesL]

Kath,
That is helpful, thanks. I have too much dappled shade on my property so that won't be a problem. Hadn't really considered the wind issue, but that's a good point.
Now thinking about rigging a windscreen to the top of a old kitchen cart so they can be wheeled right in and out of the garage.
We had one of the warmest, and driest March's on record here on LI, except for last week. Saw a lot of night time temps similar to ljp's, and tonight looks like the last night on the extended forecast where it will be in the mid 30's. Plants did not seem to have any issues at all with the lower temps, and the garage tends to hover a few degrees higher than outside.
Might try to start an outside regimen as early as next week, with the intent of going fully out the last week of April.

[lakelady]

I tried cold treatment on some of my earlier starts, which I did intentionally in case I lost any and had to resow. They are doing pretty well, but some still have that purplish cast to the bottoms of the leaves and I'm wondering how long it takes for that to go away? We'll see how they do on plant out and performance this year.