How to Build a Cold Frame to Extend Your Growing Season
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How to Build a Cold Frame to Extend Your Growing Season

August 27, 2019


We made a lot of progress this week
preparing our winter garden for the cold. We set up the PVC hoops for our new poly-tunnels and built two new cold frames, which probably look familiar, because
they are made mostly from our old cold frames. We’re expecting temperatures near freezing tonight so it’s great to have these projects completed. Today I thought I’d share how we build our cold frames, which are our favorite season extension tool short of a walk-in hoop house or greenhouse. According to Eliot Coleman, cold frames
create a microclimate that is one and a half zones or five hundred miles to the
south. This advantaged allows us to grow cold hardy crops in zone 5 well into the winter. Soon I’ll build a hoop house over this entire area, which will effectively move our cold frame microclimate even further
south – well into zone 7 or even 8. You can often make cold frames entirely from salvaged materials. Discarded windows, glass doors and shower doors make great tops. These tops came from a control room in a recording studio. You can also use salvaged wood for the frames. This cold frame is typical of how
we usually build them. The frame was built to match the dimensions of this re-purposed refrigerator shelf. We used a wider piece of wood for the back panel than the front and cut the side panels from the depth of the back panel down to
the depth of the front. We place the cold frame cut side down sloping south toward the sun. Please use this link if you liked to see exactly how I made this cold frame. Unfortunately, construction of these cold frames was a little more tricky. I had to make some design changes to accommodate the large tops over a narrow garden bed. Ordinarily, the front and back of our cold frames are at a right angle with the top of the frame. However, to make these frames fit on the garden bed, I had to make the back panel at a right angle with the bottom of the frame instead of the top. I also needed to make the slope of the cold frame much steeper to fit the large tops over the narrow garden bed. This is actually a good thing because it will allow more sun into the cold frames. Now let’s take a look at how I built the side panels from two 2 by 12’s that were cut to 42 inches to match the size of the glass top. Though the glass top is 42 inches, I want the base to be only 36 inches in order to fit on the raised bed. As a reference, I cut a strip of wood to 36
inches. Playing around with a square and the 36 inch strip of wood, I determined
where to make the cuts for the bottom and back of the panel, l resulting in a 36 inch
bottom, a 42 inch top, and a right angle between the bottom of the panel and the
back. I marked the cuts with a pencil, joined the 2 by 12’s together with deck screws, and cut the side panel. I then used the first side panel as a template to mark the cut lines for the other side panel. Again, I joined the 2 by 12’s together with screws and made the cuts. This gives you a better idea of what one of the side panels looks like on the bed. The cut side is down. The front slopes forward which allows more sun into the cold frame, and the back is at a right angle with the bottom. With the side panels complete, it’s time to move on to the front and back panels. The front panel was easy. I started with a 46 and a half inch 2 by 12 and stripped it to 10 and a half inches to match the depth of the front of the
cold frame. I drilled pilot holes with a countersink drill bit in the side panels for both the front and back panels. I then attached the front panel to the side panels with deck screws. The 46 ½ inch long front panel, combined with the side panels, matches the 49 ½ inch glass top. I built the back panel in place with boards cut to 46 ½ inches. I started with a 2 by 12. I then added added a board salvaged from an old cold frame. To finish the back panel, I cut a board to match the angle of the top. I marked the angle with a pencil on both ends, drew a cut line between the 2 lines, adjusted my saw to match the angle, cut the board to size, and attached the board to the side panels. Now that the basic box is complete, I’ll use scrap wood to reinforce the corners and cover the seams between boards. I used scrap would to reinforce all four corners, making sure to fasten the scrap wood to both panels on each corner. I also joined together the boards on the back panel with scrap wood. Finally, though it was probably overkill, I covered all of the seams between boards with scrap wood. This cold frame will last several years just as it is, but it is vulnerable to rot where it comes into contact with the soil. So, to address this problem, I’m going to use a trick I learned from Eliot Coleman. I’ll cap the bottom of the cold frame with 1 by 2’s. The 1 by 2’s will protect the wood from rot, and they can be replaced every several years as they decompose. I capped the bottom of the cold frame with cedar 1 by 2’s that we used as plant stakes in the past. The 1×2’s will keep the pine frame away from the soil and protect it from rot. They should last several years and can easily be replaced in the future if needed. The cold frame construction is now complete and in a moment I’ll put the lid on, but first I need to prune these tree collards, which I hope to overwinter in the cold frame. With the tree collards, we’re hoping to create a zone 8 microclimate in this cold frame that will enable them to grow as
perennials here in zone 5. In addition to the tree collards, we’ll be growing a wide variety of cold hardy crops under protection this fall and winter. Currently, lettuce, Swiss chard, kale, and red veined sorrel are some of the more visible plants. But if you look closely you’ll see a wide variety of self-sowing plants just getting started. In this tiny patch of soil alone, volunteer mustard, giant red mustard, and red veined sorrel seedlings are emerging. The wispy green leaves are claytonia seedlings, which are a favorite cold hardy crop that will provide salad greens all winter and into the spring. With our cold frame and poly-tunnel construction now complete, it’s time to turn my attention to
building our new walk-in hoop house, which will cover this entire raised bed. I hope to finish that project in the next 3 or 4 weeks, and plan to bring you along to share my progress. Well, that’s all for now. Thank you very
much for watching, and until next time remember you can change the world one
yard at a time.

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  1. Since we are both in the same zone, it is wonderful to watch how you extend the growing season. Hard work pays off Patrick. You are indeed a passionate gardener

  2. Hi Patrick! I just love your videos and how you share all of your garden experiments.

    Will love to go on the journey of the hoop house with you! I am in zone 5a but surrounded by zone 5b. Would love to to "zone up" by trying some of these ideas out!

  3. Looks like my OH has a new project for winter!😉 A great idea Patrick and it's going to be so beneficial to your tender plants, thanks for showing my OH (and me) how to do this.Always informative and may I say, your garden is looking fantastic!

  4. I made a cold frame last year out of scraps of wood and used some poly for the top. Worked very well. I keep looking for someone getting rid of an old window or door. No luck yet. Best wishes Bob.

  5. I look forward to see how you do my friend ! Next spring I'll be working on a similar project where I'll be looking to convert 1/2 of one of the main beds into a miniature greenhouse for cold hardy crops.

  6. That is a very nice design Patrick. Those will work nicely inside your new hoop house when you stand it up gaining another zone.
    Chuck

  7. love your channel! Here in middle of Norway we are now starting to have froztnights too. So a coldframe is a very nice low-tech solution indeed. Thank you for all your information/inspiration.

  8. Great video. I really like the design of the cold frames, and I love that you show exactly how you made them, so someone relatively new to gardening (like myself) can follow the method you used. I live in Norway, so cold frames are definitely something I want to look into for my gardening. Thank you! As always, I really enjoy your videos.
    Inger

  9. this video give me some new ideas for cold frame design, thanks for sharing with all of us, with all of your videos, i have made some changes in my garden and seasonal activities… to me, gardening is personal activity, so, i like reviewing ideas and keep creating better ways to grow more food, yours is one my top youtubes to follow and learn different or new ideas… thanks william.

  10. Great information from start to finish. Well done. Everyone is looking forward to your walk-in hoop house.

  11. I'm confused on cold frames vs. low tunnels. Eliot Coleman doesn't seem to like low tunnels. I see you use both. Te low tunnel seems easier and cheaper to build. What are the benefits of each? Should I use both for different things?

  12. Not that I need a cold frame but I found this video interesting nonetheless. Capping the base isn't something I would have thought of but I'll take every wood work tip I can get! Nice one Patrick, cheers 🙂

  13. Can you show a video on how you set up that pvc piping and what you are going to do with it? I'm very interested it that. I did enjoy the cold frame info. Especially the 1 x 2 across the bottom. I will not forget that great tip.
    Cheers from VA zone 7
    Louise
    To plant a garden is to believe in the future

  14. I like how you do your videos. They seem so professional. This reminds me of my mom, who used to do cold frames in the spring, and to start new plants. Hers were not so well designed, but they did the trick. Keep up the great work!

  15. Beautiful work Patrick, I wish I had wood working instead of home ec in high school LOL Can't wait to see the hoop house!

  16. Very nice. Glad I live in 8a. Too much geometry for my little brain. 🙂 If I ever move back to the north, I'll get somebody to build me some of these. I can't imagine not having greens in the winter.

  17. The effort to keep the topside as large as possible will pay off Patrick.Winter sun and natural light/heat to the max.Great job.

  18. Wow Patrick you never cease to amaze me, this is awesome, seems like a lot of work, and that's why your garden looks Reign Fabulous!!!!

  19. Great design, Patrick. Fitting the frame to existing glass available is an excellent idea. Ripping 1x2s from old (or new!) cedar fence boards for the bottom protection of the pine would be a good idea, too.

  20. Very nicely built cold frames and I really love the idea of replacing the bottoms with cedar steaks to protect your frames. I can't wait to see your green house. Best Wishes, Peaches

  21. I've been following your channel for months, so it's high time I said thank you for these videos. I'm in zone 4 and have bookmarked some of your methods to try in our little Zone 4 garden, starting this fall. Off-topic questions: Is that you playing the guitar intro, and what's your cat's name?

  22. Nice one Patrick! By the time you've finished with that garden o' yours you'll have made a micro climate that imitates the equator!

  23. Patrick, your garden is amazing and your videos are always inspiring even when I'm not feeling it. I was thinking today I need to build some beds etc. this winter while I'm bored, now I'm going to have to attempt at least the simple version of your cold frame boxes, my carpentry skills aren't what yours are though, you make it look easy. I've got more leaves than ever this fall and still have more on the way. This year wasn't my greatest with the months of rain on end but we still ate very well out of the garden and so did some critters, major critter problems this year. I'm thinking maybe an out of control raccoon. If you need an idea for a video, advice on how to deal with very destructive critters would be awesome.

  24. I went to poly only, since my glass tops broke last year due to so much ice in zone 5.    Using double poly layers works very well, and has some flex so that ice does not affect it.

  25. We tore down our deck. I didn't lay out my garden conveniently to build a walk-in hoop house, but I'm so excited to build some cold frames, and maybe new raised beds.

  26. Love your videos and thank you for sharing. Are your cold frames set on top of your raised bed frame or inside the raised bed frame? Planning to make some this summer and wasn't sure which would be best. Thanks again, Maggie

  27. Can kale be "cut and come again" or does one need to plant it in succession fashion for continuous harvest? I am zone 5.

  28. I Love the idea of (2) 2 X 12 boards stacked to allow more grow room for taller plants. Collards do get tall. I am wondering what is the purpose of the sloped frame? Is this just for aesthetics? I could build a box and put a window on top that is not sloped.

  29. I am so glad i found your, great videos. I will be building a hoop house too…why not? Veggies and woodworking, whats not to love ?

  30. cheers mate thanks for sharing this, great idea with the sloping front, prevents shadow zone!! nice one! Surprised you didnt treat the boards at all?

  31. Patrick, I'm planning to use the cedar 1×2 bottom cap idea to help lengthen the life of my raised bed. Comparing this video to some of your others (raised bed, keyhole, cold frame v2, etc.), it appears you used the bottom caps only on these cold frames. Any particular reason why you choose to not install them on all your other beds? Thanks for your videos!

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