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Four Season Vegetable Gardening

Cold frame on a concrete patio

19 years ago

I found plans on the internet to build a simple cold frame using plastic window well covers (they look like giant clear plastic seashells) turned on their side and nailed to a frame made of 2x4s cut to fit. I'm going to put it on my concrete patio, and I was wondering what I could put under my plant pots as insulation--a rubber mat with holes cut for drainage, maybe? Has anyone used cold frames on a concrete patio and, if so, how do you insulate plants and seed trays against the cold concrete? Thanks a lot.

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Comments (4)

kathicville
19 years ago
Hi...I noticed that no one has been able to give you an answer so far. I use a plastic-covered 2-shelf 'grow rack' on my somewhat enclosed porch, which boasts a VERY cold tile floor (with a concrete slab underneath). To try to minimize the amount of cold that the plants are subjected to, I stack up a couple of old fleece dog mats (donated by my canine) on top of a heavy rubber doormat. (I also use sand-filled trays and a heating cable for one shelf of this set-up.)

My cuttings and seedlings are in plastic trays, so leaking/drainage isn't an issue. Sounds like yours, however, would have drainage holes. Fleece, therefore, probably isn't the best option. Have you considered a good bedding of straw and fall leaves? Maybe 4-6" thick when compressed by your plant trays/pots? Last year (in addition to the porch set-up) I had a couple of very primitive, small 'cold frames' outside (on ground) that I used in late winter to start different kinds of lettuce. I stuffed them with leaves and nestled my pots into the leaves. They thrived, so I guess the system works, at least for plants that don't mind a bit of chill!

If that seems too messy, perhaps you could find one or two wooden pallets for free and use them as a platform above the straw/leaf insulation? Or some other, similar 'platform,' built to fit the size of your cold frame? Just a thought...!

Good luck!
Esvee
Original Author
19 years ago
Thank you, Cathi. This is good information. I have completed one of my window well cover cold frames, and it looks great. I think I have decided to put them out on the ground over a hole filled with leaves and grrass cuttings and covered with landscape fabric, instead of putting them on the concrete patio. I think my plants will have a better survival rate that way! Thanks again.
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Cold Frames (sort of) ideas and questions
Q
Comments (10)
Thank you for responding, I think I was unclear. The "portable" one wouldn't be 8" high total, I was thinking I'd need about 6-8" of soil, the box would have to be taller than that, of course. My concern is that being off the ground, the soil will be too cold from the air underneath. As to what I'd use it for, I was thinking starting seeds mainly and maybe growing things like lettuce, spinach etc, earlier and later. The more I think about it, the more I probably like the "permanent" box next to the trellis better. But, now I'm wondering if it will be too hot for lettuce and other leafy's there, even with the top off, on the concrete. That patio can get pretty hot as it faces east and that spot gets sun until about 5 p.m. This stuff is all trial and error for me given the spaces I have to work with. Your spot for lettuce intrigues me. I never thought under a tree would work for any kind of veggies. I do have a spot next to the patio, in my second picture you can barely see it behind the curve of pavers and potted tomaotes, where currently two dead dogwoods stand that are coming out this spring. The neighbors hickory tree shades that area and I've never had any idea what would grow there, given that in the middle of the growing season it's fairly shady a good portion of the day. Thanks again, I appreciate any advice.
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How would you finish building this cold frame?
Q
Comments (1)
What are you planning on using for your glazing (or top covering)? How are you planning on opening your cold frame when it gets too hot inside? I'm going to assume that you have typical 8x8x16 cinder blocks. I would probably remove your cinder-block side walls and use plywood instead. I would frame the top of the back-wall and front-wall cinderblock with a 2x8 board. I would then put a piece of plywood to frame the two side walls with a 2x4 sideways to act as "joists" for that angled side wall (near the top). You could use the extra blocks to make your cold frame larger or for another project. I would then frame the glazing with 1x2 boards with weatherstripping on the bottom so that when it rests on your 2x8 or 2x4 boards you get a mostly weather-tight seal. I would hinge the top and add an auto-lift-vent to the bottom. If you plan to continue to use your side-walls I would modify your top row so that there are no bricks going forward. This would give you a relatively straight run from the front of the bottom bricks to the front of your top bricks (going up 8" for every 16" horizontal). I would still then cap the ends with plywood and do what I recommend above with 2x8s on the front/back cinderblocks and a 2x4 on the side to support the glazing. At your discretion you could add 1 or 2 liter bottles filled with water into the holes of the concrete to help stabilize the temperatures (assuming the tops are capped with a 2x8). I believe your structure gives you 4ft x 2ft floor space. For all this work (and if you go with the auto-vent) you might want to consider going larger if possible. :-)
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using a cold frame
Q
Comments (1)
You should look into the Scottish Rock Garden Club site; see link below. Here is a link that might be useful: SRGC
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Update on concrete patio and patio furntiture question
Q
Comments (9)
You have to imagine how you are going to use the space first. Do you like to spend time out side. You have lots of shade, so I imagine it would be pleasant under the eaves. Then, yes, set up a table and chairs to eat out side with a server. Conversation places, to lounge and talk, etc. Just as you would in a large indoor space. I love the look of the bertoia chairs, but I find them very uncomfortable to sit in for an extended period. A pair might be nice outside the master with a little table for a cup of tea in the morning or a glass of wine before bed and would be nice to look at otherwise. In a hot clime, I wouldn't want metal furniture because even the frames conduct and radiate heat. I'd look for teak or wood. In your price range you may be able to find an original designer who's work you like. Sometimes, for outdoors, all a wood indoor piece needs is a different finish, which you can order as for from a custom or original designer. There are thousands of brilliant furniture makers out there working in wood, Mark Tuckey comes to mind.
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kathicville
19 years ago
You're welcome! Good luck! One other thought: I wonder if there's any value to using the double-sided silver insulation stuff that comes in rolls from your local big box hardware store? (In my house, I used it to insulate the space behind the pipes of my kitchen sink, to keep them from freezing. Works like a charm.) It's not cheap, but it IS reusable...........You might also post your question on the greenhouse forum. Those folks are passionate about finding inexpensive ways to keep their wintering-over set-ups toasty...........Have fun!
jonathanparker
14 years ago
I feel mineral wool insulation is perfect for insulating against cold concrete its resistant to moisture it has a lot of body and will keep cold from creeping in.

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