Using Cold Frames in a Northern Winter — Update

This year Yankee Bill built me some lovely cold frames. They are made out of reclaimed lumber from a building that was being torn down by his NY Guard unit and two glass doors.  One of those doors-an old sliding glass door-we’ve had since before we moved in to the Frugal Upstate Village Homestead– because I “someday” I was going to have a cold frame.  Well someday arrived!

Anyway-the doors have solid frames, real glass (although shatter proof) and were heavy.  Really heavy.  So Yankee Bill rigged me up a rope and pulley system to raise them.  The picture below was snapped right after he put them together (I was sharing my excitement on Facebook) so only one of the frames has been rigged up with a pulley and he had yet to put the cleat on the wall of the shed for me to tie the rope off to.

Learning Point:  Using recycled materials is inexpensive and effective–but if you are starting from scratch and buying supplies consider the weight of the tops.  Many folks recommend using some types of rigid plastic.
FYI-that plant you see in the foreground? That’s lettuce going to seed.  I let it flower and go to seed then saved my very own lettuce seeds!  I’ve got pictures-I’ll eventually get THAT post written 😉

Once the frames were all together I planted them up.  I took a few chard plants that were small out of the garden and also transplanted some Kale that had self seeded elsewhere and were little tiny seedlings.  I planted a couple of rows of lettuce, mizuna etc.  In the other frame I added some turnip, onions and more.

It really was a bit late–the end of August.  I don’t think “fall garden/winter garden” till late August early September, but really most crops SHOULD be planted in mid July in order to grow enough before the cold sets in.  The whole idea of a cold frame (or a winter hoop  house) in our northern latitudes isn’t really to grow a lot–it’s more to preserve plants that have already grown.  Once you hit freezing temperatures not much is going to keep growing but certain well chosen crops can just sort of hang out, be harvested and then keep growing in the spring.

The second frame really hasn’t done much with the seeds I planted in there–I started them too late and didn’t choose things that were cold tolerant enough.  The salad turnips have been very slowly growing and will probably take off in the spring, but most of it is wasted space.  I guess I can just chalk it up to experience–and know that I’ve got space to put my flats of seedlings in the spring!

Learning Point:  Plant much much earlier!  Start seedlings indoors for plants that can’t take the heat when the planting TIME is right.

After a few weeks things were growing nicely.  I was able to just leave the tops all the way open most of the time for sun, rain and heat to work their magic.  The rule of thumb according to what I read was: Under 40-shut the cold frame, 40 thru 50-vent the cold frame, over 50 open the cold frame all the way.

One of the things I was looking forward to was a lack of pests in my cold frame.  Most of the articles I read talked about how fall/winter gardening was more pest free, that the temperatures put most things into hibernation or killed them.  Apparently no one told the cabbage worms in my cold frames that.  They did quite a number on my Kale:

I tried just picking and squishing at first, but finally had to go a bit nuclear on them.  I bought BT (Bacillus thuringiensis) to spray both my cold frames and my outdoor rows of kale.  Basically it’s a microbe that specifically kills cabbage worms and a few other select pests.  Although I prefer not to use any kind of pesticide if possible, I like that this is natural and targeted–I’m not going to accidentally kill ladybugs or bees or anything.  Next year I’ll try some of the more preventative measures with my cabbage family plants-like putting floating row covers over them so that the moths and such can’t get down to the ground near the stem of the plant to lay their eggs.

I’ve also found little tiny slugs in there that seem to like the heat and humidity.  I probably should put some beer traps in there or something.

Learning Point:  Cold frames are not automatically pest free–check them regularly and take action early.

With a fairly warm fall I had to remember to vent the cold frames.  Since you are planting them with cold weather crops, too much heat is not a good thing!  Yankee Bill figured I was going to cook everything in there by accident at some point, but I managed to keep everything alive.  I hope I can be as good at remembering this coming spring when the weather heats up again.

We had a very mild early winter with a very, very late snow fall.  The plants inside the cold frames were able to keep growing much longer than I expected.  In mid to late November I was still able to walk out there and pick myself some great looking greens.

Inside the mini hoop house which went up about a week after cold frames the radishes and bok choy were starting to gain ground as well.  I was able to pick some of those for winter salads.

It was really amazing to be able to put together a completely home grown, fresh picked salad from my garden in November!  A variety of greens, salad turnips, carrots, some garlic greens that poked up and some tomatoes. (of course it had dehydrated cherry tomatoes–none of those in the winter unless you get heated and expensive!)

Finally, just before Christmas the snow came.  I was stuck in a bit of a quandary.  What do I do now?  Do I leave the snow on for insulation?  Will that cause problems because the sun can’t get in and warm the air in the frame at all?  Do I brush the snow off?  With the colder temperatures will removing that insulation cause things to freeze?  And what about actually harvesting things?  If the temperatures are cold and I open the cold frame am I letting out too much precious heat?

ACK!  I googled.  I read.  I tried to find answers.  Nobody seemed to address this particular issue.  Finally I found a single paragraph in Eliot Coleman’s “Four Season Harvest” (the absolute bible for growing things year round in cold climates-if the man can harvest fresh vegetables during a Maine winter, I can grow things in the comparatively balmy NY winter!)

Coping with Snow:

Most of the time, we clear the cold frames of snow so the sunlight can enter.  We use a heavy bristle push broom to do the job. . . sometimes we leave the snow on the frame for insulation if the weather report predicts extra-cold temperatures for a few days following a snowfall.  The plants don’t mind the dark, and with the extra insulation, the frame temperature won’t drop as low.  When we’ve been away and not cleared the frames for many weeks there haven’t been any problems.  Remember, the plants are not growing, just hibernating.  They don’t mind some snow.  (Coleman, The Four Season Harvest 103)

All righty then!  I grabbed the broom out of the garage and swept off the glass.

Used the pulley to pull up the glass about 10 inches and tied it off.

And peeked inside.

Lettuce, chard, mizuna an kale were all still alive if looking a bit wilty.  I cut some lettuce and chard and called it a day.  Since then we’ve had a rather major thaw where I was able to get out there and harvest a few more things. It’s now snowing again.

If I really wanted to feed my family out of the cold frames I’d need to plant a lot more food in there.  I’m thinking that if they act more as “cold storage” in the winter than actual “growing space” that maybe the most efficient use of just a few cold frames is to transplant in almost fully grown plants in late fall at a tighter spacing than I’d normally grow at and let them go into hibernation for the winter.  Then as I harvest them I’d be providing more room so that the plants left in the spring (if there were any) would have room to spread and grow and provide earlier greens than what I can plant in our cold wet NY ground.

I’m also looking forward to seeing if some of the plants that tend to be a bit more “cut and come again” like the mizuna and chard will put out new growth in the spring that can fill in that timeframe where it begins to be warmer but yet is too early to plant.

The cold frames and mini hoop house should also be getting a big workout this spring when it’s time to take my little seedlings out of the basement yet it’s too cold to leave them unprotected overnight.  I can have them in the frames so that I don’t have to monkey around with bringing them in and out and in and out and. . . well you get it 😉


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  1. says

    I’m so glad they are working out for you! Down here in FL, we only need collapsible hoop-housing for cold snaps. I’m going to try to do year-round veggies at my new place, although not much grows in the summer (too hot), so I’ll have to resort to microgreens and sprouts grown indoors for leafy stuff.

  2. says

    Thanks for sharing what you did! My husband and I have talked about doing a cold frame so that we could have a few things in the winter and I think this is the motivation I needed to try it.

  3. says

    Did the hoophouse plants live? I’m thinking about ordering a smaller version of this, and starting plants in it now. (Jan.) Just to see…

    and we’re at a northern latitude, too. (Colorado) But we do get a LOT of sun here.

    Thanks so much for this update, Jen. I wasn’t the only one who was wondering how the coldframes were doing.

    • says

      Cindy-I’ve still got radishes, turnips and Bok Choy that seem to be doing find in the mini hoop. I know you couldn’t start plants in it now–but I’m going to start under lights in the basement soon, and that taller hoop will be a BIG benefit when I’m messing around with tomatoes & peppers in the spring 😉 If you haven’t read Eliot Coleman’s “Four Season Harvest” you need to–tons of great info on this kind of stuff.

  4. says

    I don’t have experience with cold frames, but I recently acquired a couple sliding glass doors that I want to turn into cold frames this spring. There are a couple thoughts I had about the cold times, where you struggle to decide whether to clear the snow from the tops:
    -use a couple packing quilts or thick blankets to lay on top of the frames at night to help keep the warm inside
    -stack straw bales around the frames to absorb heat during the day and release the heat/insulate at night

    Those are a couple ideas I plan to try. The quilts don’t need to be used all the time and the straw can be cycled every couple years into compost or mulch and replacing it with fresh.

    • says

      John-Those are some great ideas! Hay is supposed to be a great insulator–I’ve read about folks just using hay bales for the sides and then putting some sort of light/glass/etc on top. Where mine are placed now I probably could only get bales around 3 sides–which might still help. I’ve also considered finding some sort of insulation material (styrofoam? Some sort of construction foam board?) that I could use to line the interior of the frames. The blankets would work well-but you’d have to find some way to ensure they stayed down in the wind–I’ve had issues with the bottom part of my mini hoop house being caught by the wind and blown open (and it’s weighted down with a 2X4). I had also toyed with the idea of painting a bunch of milk jugs black, filling them with water and setting them inside to act as a heat sink but didn’t get around to it this year.

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