Heated coldframe plans or ideas

swanzeyguyFebruary 18, 2004

Hi, I just discovered this site and have a question.I want

to build a good size coldframe, ( not to winter over, but

to actively grow veggies in these very cold New Hampshire

winters where it gets up to 25 below farenheit..I'm thinking

of using one of those small ceramic heaters and a

thermostat to try to keep temps 50 plus degrees..Has anyone had experience with this..Is it realistic..Can a uniform temperature be maintained in a coldframe using a thermostat ,or would a coldframe being smaller than a greenhouse fluctuate too much in temperature range..Any suggestions would be appreciated..Thx


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faithling(z4 VT)

Trying to heat and actively grow vegies in the northeast in a cold frame without supplemental light during the dark months (between Halloween and Ground Hog Day) sounds like a lost cause and a big waste of energy. I'd speculate that you'd use a lot less energy growing veggies indoors with grow lights.

For season extending, I've tried working with cold frames in the past but found all the bending over, cleaning the snow off, and lifting the covers to access the beds (and vent them) felt way too much like work. I much prefer my hoop house where I can walk in and benefit from the protected environment along with my plants!

    Bookmark   February 19, 2004 at 11:36PM
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Bessboro(Z4 NY)

I am curious about Faithling's season extending with hoophouse. I am probably just across the lake from you seeing how we are both zone 4. Been a tough winter wouldn't you say? Anyhow, how long can you extend the season in the fall and when do you start up the hoophouse in the spring. Also do you use any supplemental heat or light or just natural. I'm thinking about a hoophouse but would like to get to know someone who could give me some ideas on what to expect for results and set me straight on how to proceed. I might add I really thought this forum would have alot more people intrested in four season gardening than it has had. Thanks

    Bookmark   February 20, 2004 at 8:48PM
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Thanks Faithling, I would definitely try a hoophouse if I had the yardspace. Your probably correct about the light needs of a coldframe..Just wanted a to have a small, actively growing space that would keep the winter doldrums away..


    Bookmark   February 20, 2004 at 10:03PM
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faithling(z4 VT)

Yeah, there's no getting around it -- the winter doldrums can be brutal. But I get a lot of pleasure from my indoor plants in winter and have had little snibbits of flavor from potted rosemary, cilantro and arugula in the sunniest windows and nice colors and scents from forced bulbs, african violets and geraniums. Every little bit of plant life helps.

I also get a kick out of growing belgian endive in a closet in the house and "harvesting" really good quality cabbage and root vegies from my root celar.

Definately read Eliot Coleman's "Four Season Harvest" for other great ideas for getting through winter and extending the growing season.

As for the hoophouse, it's just one layer of plastic over hoops with beds that were planted with cold hardy vegies in the fall. No supplemental heat or light. Some of the beds were timed for late fall harvest and others for spring. The beds are covered with remay for extra protection while overwintering.

I've been checking every day to see if the warmer daytime temps are making any progress in thawing the frozen ground in my beds. Still hard as rock an inch below the surface. It's going to be another late start this year -- but the sun is getting stronger every day!

    Bookmark   February 20, 2004 at 11:40PM
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Thanks Faithling, it was Eliot Coleman's Tv show "gardening
naturally" that got me interested in gardening.His books are
great reading, I borrowed from library and read from beginni
ng to end.Been a cold winter here in New England, but days
are getting longer and brighter.

    Bookmark   February 21, 2004 at 8:36PM
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yooperjon(Up Mi. z4/5)

Hey folks,
A tip for thawing your ground out earlier;
Frost (Ground Freezing) enters into your hoophouse from the sides on an angle. Line the outside foundation with straw bales to slow, and sometimes eleminate freezing in mild years. Jon

    Bookmark   March 12, 2004 at 1:24PM
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micropropagator(zone5 S Indiana)

I have noticed for many decades that winter onions, lettuce, and other winter-growing crops are 3 times as tall among falled maple tree limbs and other trash. This spring I falled to get a cold frame covered and planted. Weeds grew 3 times as tall in it as in the open space beside the cold frame. Any sort of winter protection is useful and gives you bigger spring vegetables.

I regard my fall root crops as my most important garden. I have been eating from my August turnips since September and it is now May 15 and they will be useful until June 1 this year from the root cellar. Asian winter radishes do not last beyond May 1. Meanwhile, I am eating the seedstalks of turnips that I left in the garden overwinter buried under leaves.

Harold Eddleman

    Bookmark   May 16, 2004 at 12:45AM
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plantman532000(z5 NcntrlPa.)

Many years ago I made a small cold frame for winter growing. It was about 2'x6' and the base was 12 inched deep with a (I believe) equalaterial (both sides the same size) triangle shape when viewed from the side in stead of a right angle. The base was actually a 2'x6'x16" deep planter with the triangluar top set on of it. It had a bottom and was set up on a pair of saw horses. I filled it about half way with potting soil. I used a line voltage greenhouse thermostat to operate a heating cable in the soil and (I think) two 60 watt light bulbs to heat the air. I had 2 inches of foam insulation under the bottom and around the sides as well as in the north roof. Inside was reflective white. the cover had 2 layers and a heat acyivated vent opener to vent it.I also would cover it at night on the really cold nights. It was really a joy to be able to grow things in the middle of winter. It wasn't big, (I'd loved to have had a bigger one) but it didn't cost much to heat here in central Pa.

I grew lettuce, chinese cabbage and lots of cool crops AND was successful in growing TOMATOS! Tiny Tim, the sub/artic series including S/A cherry (really wish I could find that one now!) siberia and severial of the other cool tollerent types available from Tomato Growers Supply.

I haven't had it in years, but I may build a new one for this fall! Been thinking about it for a while now. I have a very small yard and zoning won't allow a hoop house like I want. Good luck.


    Bookmark   May 21, 2004 at 2:09PM
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Thanks John..Something like that is about what I was thinking . I have the same problem with ordinances , and just wanted to have fun growing something during the cold months..PUTTING IT up on sawhorses is a great idea, helps with the snow we get around here.

    Bookmark   May 21, 2004 at 10:37PM
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plantman532000(z5 NcntrlPa.)

Hey Swanz, Check out the Accessible Garden forum! There is a post from June 3 from cyngbeld with a link to what they called an accesible cold frame. It is a site from Western Red Cedar Lumber Association. I checked it out and WOW! It looks great and could easily be insulated and set up for winter growing just like the frame I made years ago. Only I'd make it bigger than the plans call for, and add a solar vent opener like I used before! LOL Just go to the site and you can even print out the plans. Just thought you'd like to see it. Good growing.

    Bookmark   June 7, 2004 at 9:14PM
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amin(4 MN)

I recently read a great book that may interest you titled the solar garden. They recommend creating an insullated bed by digging the edgesinto the dirt, and insulating this. You can create a passive heat supply with a black barrel of water that will collect heat in the day and slowly release it at night. They have a design for insulated solar pods, (but I may try to do something with 2 layers of old storm windows insulated w/ a couple layers of bubble wrap between. )

Its best to cover the winter beds at night.and you are supposed to keep the snow off the top. (but leave it around as this is extra insulation)

Also I have seen other plans if you have a south facing slope, you can dig in and create asunken bed with the top slanting twords the south, as underground the temp stays an even 55 degrees (supposedly)

There are many ideas I have come across for heating (to many to list) but the greater problem would seem that depending on what you want to grow there may be insufficient light in winter. I have heard great success stories even in my zone four for growing lettuce, arugala, spinache, leeks...and other cold tolerant veggies, most of these suggest the plants still go dormant in Dec. and Jan.

    Bookmark   June 17, 2004 at 7:42AM
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Thanks John, gonna check out that site..I promised myself I'd build something this summer..Thanks Amin,,I think a black barrel of water would just turn into a block of ice without supplemental heating.I've read about the sunken bed concept before, the only problem being, ( as you mentioned) limited light..

    Bookmark   June 18, 2004 at 11:35PM
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Millie_36(Z6b MO)

Swanzeyguy, I remember seeing it done in Northern Germany, but not sure "how" it was done. The man had a greenhouse/green grocer operation going all winter. Fresh lettuce mostly...but lettuce is less cold hardy than the cabbage family. He had berms of soil built up in a field with the cold frames facing south...other than that, I can't say. I suspected that he might be using hot manure buried under the soil in the bottom of the frames. My grandfather told me that was how they built them for starting early season plants...he grew up in Illinois. Chinese veggies, lettuce, cabbage, spinach, kale, etc. needs less light. If you can keep the soil temp at 55 to 60 degrees, it doesn't take much cover to keep them from freezing. We use hot water lines under beds in an unheated greenhouse. Only need to run the hot water when it really gets cold... then on a bad night, toss some floating row cover over the lettuce, spinach, etc. It traps the warm air rising from the soil. Only loss has been leaves that touch the plastic on the sides of the greenhouse. The beds are built right up against the outside cement block foundation. We did line it with some 1 inch styrofoam. Square bales of hay would be better, but haven't needed it. I have used hay bales to build a raised cold frame, but not in country as cold as you deal with.

Works great for winter propagation of woody plants...keeps cutting bottoms warm for rooting while the tops stay cold, so they will stay dormant.

    Bookmark   July 21, 2004 at 8:58PM
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Thanks Millie, it's fascinating all the different techniques
that can be used..That method of propagating woody plants
sounds like something I'd like to try.


    Bookmark   July 31, 2004 at 9:49PM
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Hi Swanz
I have a heated cold frame that I use for starting flowers and veggies. It's made of 2" thick styrofoam that is framed with wood.I use a 1500 watt ceramic heater that is operated off a thermostat I also have a ventilation fan also operated off a thermostat to help with cooling. The box is 4' X 8' I use three wood framed sashes double glased with plastic to cover it. I has worked well for me for the last 4 or 5 years.

    Bookmark   August 8, 2004 at 9:55AM
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Thanks Don, I bought one of those small ceramic heaters,just
gotta get a thermostat,been checking around, they're pretty
pricey, 50.00 dollar range and up.


    Bookmark   August 12, 2004 at 9:45PM
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Another book that has some great plans for frames and cool season gardening is gretchen poisson- solar gardening. frames look a bit pricey but innovative and quite nice.

    Bookmark   September 8, 2004 at 11:53PM
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byron(4a/5b NH)


A combination of old and new.

Near the ground I use peanuts for insulation to get some R value

For old, I used horsemanure as in the Hot bed concept.

Horsemanure plus a few 40w bulbs within a small area, 2" styrafoam for a night cover will keep your plants above 50F when the outside temps are 18F


Here is a link that might be useful: My GH

    Bookmark   September 28, 2004 at 1:03PM
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Thanks Byron, enjoyed those photos.


    Bookmark   September 29, 2004 at 7:34PM
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bluemill(zone8,9,10 ca.)

i made plastic 6' "pup tents", which are easy and work well. e mail me if you would like more imfo. and i use dark colored buckets of water, which collect heat during day and release at night. got idea from elliot coleman book.

    Bookmark   December 24, 2004 at 6:08AM
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