A simple cold frame is an easy, economical way to get more out of your garden.
Salad ready to eat in January
You might know that I built a small greenhouse this fall. Unfortunately by the time I finished it in early November it was pretty late to get started – I have a few things going in there now, but I’ve not really been able to use it to full advantage. Being able to enjoy the sunshine while I’ve worked in there out of the cold has been nice. But the truth is that so far this cold frame has been at least as productive as the greenhouse.
While I built my greenhouse on the cheap ($50 out of pocket) building this cold frame actually cost nothing – 100 percent recycled materials. Not only that, but the design is so simple that anyone should be able to build one in an hour or two once you scrounge up the few things that you need. The glass for my cold frame came from a sliding glass door – it started life as double pane glass, but a lawnmower thrown rock converted it to single pane – it works great. You could use just about any piece of glass – as long as it isn’t tinted or too large or small - just build the wooden parts to fit the glass pane that you have. I must say that it is very convenient that mine has a frame around it instead of being just a plain piece of glass, but don’t let that stop you if that’s what you come up with.
The principle is about the same for a cold frame as it is for an unheated greenhouse – inside it’s like your plants are spending the winter 2-300 miles further south – maybe better. They’re protected from wind, cold rain, low humidity, snow, and many frosts. It’s not like they’re in the tropics, it’s just that winter is a lot milder inside of a cold frame. One particularly warm day at the beginning of January it got up to 87 degrees (F) in mine but even though that sounds really hot I don’t think that it’s the same as an 87 degree day in August – the ground is cool and there just isn’t so much radiant energy. Anyway, it didn’t seem to bother the lettuce and spinach that was growing in there. You can probably treat it like it’s at least one zone warmer – Instead of planting arugula in March you can plant it in January – and you also get an extra month in the fall.
Wouldn’t it be better if the glass was at a steeper angle, the soil was in an insulated chamber, everything was weather stripped, the inside was a nice reflective white, and it had an automatic vent opener? Maybe, but it works really well just like this. The truth is that if it was all that complicated or expensive I probably wouldn’t have built it to begin with. Also the fact that it’s a bit leaky probably helps to keep it from overheating and might be more important than keeping out every possible draft.
This picture makes it pretty clear how this works - when it starts getting cold I put boards on the ends to close up the gaps. If you live even farther south like my sister in Mississippi you might just want to leave the ends open.
Isn’t that plain spruce lumber and chip board going to rot? It sure will, but 1) I try to avoid using treated lumber in the garden if at all possible 2) Rot resistant wood like cedar and redwood are uber expensive 3) Nothing lasts forever 4) It was FREE – scraps, culls, and reclaimed materials. When it does rot I’ll replace it with more scrap/recycled material.
Wouldn’t a plastic tunnel work just as well – maybe, but it’s a lot more trouble to open one of those to do anything – the convenience of being able to just tip the glass up means you’re more likely to take care, and pick food out of it. Then again if a plastic tunnel is what you’re up for then by all means go for it – it will get the job done.
Because of the simple design when the weather warms up I can move the whole thing out of the way, or I might move it over some strawberries and replace the glass with a screen to keep birds out. It would also be useful like that for keeping vine borer moths off of young squash plants.
As you can see there aren’t any hinges. The glass just sits on top, and the piece of wood where the hinge would be keeps it from sliding off when the lid is propped open. The 2×4 just elevates the back so that rain drains off - The glass comes off to make it easier to work in – The whole thing just sits on top of the ground – I pushed a bit of soil around the bottom where needed to fill any gaps.
On a sunny day it can get 20 degrees warmer inside of the cold frame than the outside temp.
Where to put your cold frame – In a place that gets as much sun as possible, and remember that the sun will be lower in January than it is in September. I set this one right over an existing raised bed that already had very good soil, and if you have a choice try to put it close to the kitchen so that it’s handy to pick a fresh salad for supper.
Try to put your cold frame in a place where it gets sun all day long instead of being in the shade for a couple of hours like this. It wasn't like that in October.
Other Resources
Cold Frames and Hot Beds – Cornell University
Good ideas! I have some doors that need used. I’ve been thinking about a greenhouse but a coldframe would be a good use for them until I get around to it. Good post!
You should do that – it would probably be perfect for growing out those cuttings that you’ve been working with – http://thehomegarden.blogspot.com/2009/01/rooting-yoshino-cherry.html
The cold frame is a great idea. I just “rescued” a few small windows and stored them. Maybe by the time it stops snowing around here I’ll run into a shower door that needs rescuing :~)
It wouldn’t have to be as big as this to be useful. I only tend to plant 1/3 – 1/2 of this one at a time anyway.
Also if you have 2 or 3 small sashes that are the same size you could just put them in one big frame side by side. There would actually be some advantage to doing it like that. Ventilation would be more controllable, and you could get into one section to pick without exposing the whole thing to the cold.
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I love these nested comments in WP 2.7.
That is cute. I guess it’s 2.7 upgrade time for me.
I live in Norway, in the south/west part, where we get all the cool winter storms, and fantastic summers, I was kind of hoping to start erlier with the help of a greehouse,the nature dosen`t make it easy for us up here. it will be easyer with a greenhouse like this, i hope! Im makingone this year, so thanks for all the help on this site and for the design. I have to do in my way do, hope thats ok ;-D
Have a nice life!
Absolutely – you have to adapt to your conditions, the materials that you have available, and even the tools that you have access to. All that is part of the fun!
The cold frame that I have inside my Junk built greenhouse lkooks just like yours but I have an air matress filled with water and heated by a water bed heater the heat can be controlled very well with this set up. the door as you know is very heavy but because ours is in the greenhouse I was able to hook the door to a pully system which allowed it to be raised very easily. And an added feature is that it ramains oven in any position for venting or to work it it had has to pe pushed closed which is easy enough for my wife to do. Right now the ground is covered with snow the greenhouse is only 40 degrees as it is unheated. But in the cold frame it is 75 degrees and sprouts are up and looking good. Thanks for stearing me to your blog
Bill
You know, the patio door frame that I’m using for my cold frame doesn’t seem all that heavy to me – however I’m a pretty big guy.
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My unheated cold frame has been really productive over this winter – it’s producing all the salad greens that my wife and I want right now. It’s so easy to build one if you don’t get all bogged down in the ideas to make it better (and more complex to build and use) every gardener should use one.
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I just built a very simple plastic tunnel – kind of like you have on your beds – over the weekend. Those are so cheap and easy, there really isn’t any reason not to have a cold frame of some kind.
I think I have become a “stumbler”! Enjoyed every bit of the site and have shared it with fellow gardeners. Thank you for the well-written instructions and insights. It was just what I was looking for.
Very inspiring and useful. Thanks so much. I’m a landscape designer and just starting to get into gardening. I have seedlings coming out of my ears right now, as I just moved and wasn’t aware of the late planting dates. I’m headed to the thrift store for cold frame materials – for sure!! Keep up the great work!
Thanks Amanda,
For the last few weeks it’s been warm enough that the lettuce and whatnot don’t need this anymore so I’ve been using it to harden off and protect bedding plants until it’s time to set them out. Now that time is here and I cam move the cold frame to a new spot where I’ll direct seed some squash for an early head start.
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Every gardener should knock one of these together.
I just made your cold frame, from free materials. today I’m going to fine tune it ,check for drafts etc. I have all seeds bought, trays, planting mix . Kmart had Burpee seeds 40% off ! so I stocked up. can’t wait to get seeds in. I’m doing flowers, & herbs. I live in Michigan. thank you so much for this simple cold frame that a age 50+ woman can do on her own.
I’d like to keep you posted on progress with pictures
thanks
Nora
Excellent! Even though the weather is pretty warm here right now it is still a bit unsettled and unpredictable. I moved my cold frame to a new spot and planted some squash – zucchini and crook necked – and cucumber seeds under it about a week ago. The resulting steamy tropical conditions in there made everything come up in only 2 days! Without the extra protection I would probably still be waiting.
I just commented on your greenhouse page. But I think this would be much easier for me to do. And I’m glad to know it works as well as the greenhouse.
(I do have a piece of glass that I got through Freecycle. It’s about 2 1/2′ x 6′. But it is just plain glass with no trim. So I’m wondering if I should have supports to keep it from breaking. There is no way to hinge it. So I’d have to slide or lift it. I may have to go with something else.)
I’m enjoying finding things on your site.
The coldframe does work just as well as my greenhouse – but with a few exceptions.
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1)When it is cold and you open the lid on the coldframe you flood it with cold air – not really a big deal.
2)When it’s cold or rainy you can work inside of the greenhouse – obviously not an option with the cold frame.
3)You can only grow plants up to a foot or so tall in the cold frame.
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However, you always have to water in the greenhouse – although not all that often when the weather is cool. The coldframe has the advantage that you can open the lid and let the rain water it when the weather is fit.
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I really like both of them a lot!
That piece of glass sounds perfect to me. The only thing that you need is something to catch the prop on when you open the lid. You could glue a flat piece of wood to it with silicone adhesive or you could build a frame around it. You could also use a prop with a rubber tip on it. You do want something that is reliable though – don’t want to break it. However, it is most likely tempered if it came out of any kind of door. Tempered glass will still break, but it’s surprisingly tough.
Love it! I had been thinking of building a low berm to the North of my garden with a row of cedars behind that as a wind block and when I saw your post I thought why not make a terraced cold frame. I picked up 9 old style storm windows this summer and it should work wonderfully. There are some things that just either don’t do well in aquaponics or are easier in dirt. My problem is I have to build any soil I grow in and dig down far enough to make sure it is clean. Thanks for the post. I think I’ll put a link to your page in my aquaponics blog.
I am having an 16 x 7 garage door replaced. It has three solid but old sections and one section with windows. I am thinking of using it as a very long cold frame. Also the metal track it is on will be replaced and seems very strong. Probably 7 ft. sections with a curve in it is almost 90 degrees but it seems that I should be able to use it for ends of greenhouse or hoop house somehow. Any suggestions?
The sections could be usable for the sides of a cold frame if they wouldn’t be too deep. For the top you want as much glazed (clear) area as possible, so unless the windows are very large you might only end up with a small amount of usable area. Also keep in mind that you will be wanting to open the top pretty often, and you don’t want it to be too inconvenient or you will probably tend to your cold frame less than would be ideal. I like your ideas though. It always seems a shame to just send things like that to the landfill. It *is* a shame.
Can you grow taller plants with this method also or just shorter types?
That just depends on how deep you build your cold frame. However you also need to take into account the low angle of the winter sun. If you aren’t careful you can have a section at the south edge of your cold frame that is always in the shade from the frame. Of course you can modify the design if you want to have more vertical growing space.
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