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Greenhouses & Garden Structures

Starting Tomatoes in a cold frame

14 years ago

Is it possible to start tomatoes in a cold frame? If I would start the tomatoes indoors and once they germinate, take them out to a cold frame - would they survive and continue to grow? If possible, I would like to get the tomatoe starts out of the house once they germinate. I actually have one of those popup flower house green houses. Would that work as a cold frame? If anybody has any helpful suggestions, I would greatly appreciate it.

Thanks,

Mike

Featured Answer

kudzu9

14 years ago

mike-
Without supplemental heat in a cold frame under those circumstances you're not going to have good results. There's simply no way a cold frame will maintain the temps you need with freezing weather at night. If your coldframe is somewhere you can reach it with an extension cord, you could use a germination heating mat. Mine are 44" X 22" and I can get 4 standard flats on one. They only draw about 100 watts, which is like a standard lightbulb, but they oould do a good job of keeping the soil for the seedlings warm, particularly if you put a piece of styrofoam
between the mat and the ground. Covering the cold frame with a blanket at night (plus a piece of plastic to keep the blanket dry) would also make your setup more energy efficient.

Here is a link that might be useful: Heating mats

Comments (7)

dcarch7 d c f l a s h 7 @ y a h o o . c o m
14 years ago
I have been doing it for many years.

Great way to get a couple od months' growint time.

dcarch
Dan _Staley (5b Sunset 2B AHS 7)
14 years ago
Is it possible to start tomatoes in a cold frame?

Sure can, if you can get your soil temp up and keep it up.

If I would start the tomatoes indoors and once they germinate, take them out to a cold frame - would they survive and continue to grow?

That's how its done, but you have to keep it up over, say, 45ÂºF at night in spring.

I actually have one of those popup flower house green houses. Would that work as a cold frame?

If you are describing one of those 3-shelf things with about 10mil plastic and a zipper, you won't be able to keep it warm enough at night for toms, esp starting them. Most coldframes are wood sides and glass tops, preferably two layers of glass for what you want, and some way to vent in the day, either going out there and physically opening the top or having a vent opener do it. Then remembering to close it before sundown to keep in the heat.

Dan
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Hope you don't mind if I first link to your previous post on this question since it has some info in it already. You indicate in it that your zone is 6B correct? If so you really need to add that to your sign in (see how we all have our zones listed by our names. Then someone asked in the other post what seeds specifically you are talking about? We still need that info since all seeds are treated differently. So what seedlings are we talking about? Some will tolerate full sun exposure, some will require a bit of shading to keep them from burning. But basically, in very general terms and with several exceptions, you just control the temperature. And with mixed vegetables that may be difficult to do without some shade-type covering. For example young lettuces and other leafy greens won't tolerate near the same temps as tomato and pepper plants will. Leafy greens require cool growing temps once they germinate. So this first year, depending on how your cold frame is built (not to mention the excessive warm temps we are having this year) you will be doing a lot of experimenting, trial and error learning, to discover how your cold frame works. You mention both lettuce and spinach in the other post. In zone 6B those should already be out in the garden several weeks ago since it is rapidly becoming so warm they are already starting to bolt and go to seed. Hope this helps. Dave
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LOL! Well, here in Salt Lake County, UT, we have long winters & summers, and short springs and autumns. It's weird; things start warming up in late February, but there are a lot of false starts, and it's not uncommon for us to have a lone snow storm in late April, even if we hadn't had snow in weeks. I don't know the spring frost date off hand. Judging by the sources on the web, it's probably somewhere between 4/18 and 4/26 (one site said 5/18, but I think that's way off). If 'spring frost date' literally refers to the average date of the last frost, then late April seems plausible, as Winter often takes a dying gasp around then. But generally, frosts are few and far between by then. If we have a frost in late April, it usually follows a week or two without frosts, so even though late April might typically be the spring frost date, I don't know if that's the best date to go by (maybe you guys can help me figure this out). I mean, the average low creeps above freezing by March 11th, according to Weather.com. I know that this is only an average, and that in any typical year, I can expect several frosts after this date, but late April still seems a bit late to me. But what do I know? Over the last few years, I bought my tomato plants at the garden center, and I always waited until May to plant them.
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mike3
Original Author
14 years ago
Thanks for the information - I appreciate it. dan_staley, you said that you need to keep the temerature at least 45ÂºF. Is that possible in a cold frame if it is below freezing outside? It is not too uncommon to have below freezing well into March here at times.

Thanks again,
Mike
mike3
Original Author
14 years ago
Thanks for that great idea kudzu9. All of this information has been very helpful. It has given me what I need to know to think about.

Thanks again,
Mike
Dan _Staley (5b Sunset 2B AHS 7)
14 years ago
I'm at 5700 ft and my coldframe is ~44ÂºF right now, outside is ~28ÂºF, yesterday not full sun. Today will be full sun and this time tomorrow it will be warmer inside. But that is because the sun is so intense at this altitude.

Nonetheless, there are coldframes and hotboxes, where the hotbox has added heat, usu by electricity. There are soil heating cables available thru the seed catalogues, or the germination mats described above, or a string of old-style Christmas lights for added heat. In March there most people use their coldframes to harden off their crops, taking them out there in the morning and bringing them back in for the night, usu for a week-10 days. If your temps are going to be below freezing a coldframe will keep the frost off and above freezing, but not much more, as kudzu said. One other thing: control leaks. Even several small holes mean heat loss, esp in wind.

Dan
mike3
Original Author
14 years ago
Thanks for the additional information dan_staley.

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