Modified TT SFG vs. Cold Frame

middlemamma wrote:Great timing camp....

In the SFG bed, I also planted a bunch of misc. stuff: White onions, BS

martha wrote:

Boffer, I didn't know you had to plant BS (she says with the most innocent facial expression you have ever seen.)

boffer wrote:Modified SFG bed vs. cold frame

(this post is about the use of cold frames in the springtime-not autumn)

Cold frames can be a great way to get a head start on spring planting and for hardening off plants. What people rarely talk about however, is if you stick it where the sun don't shine, they don't work very well. I had a thermometer in my cold frame until it broke; I haven't replaced it. If I want to know what it's like inside the cold frame, I get in my car. If it's 20 degrees F, with snow on the ground, and the sun is shining, it can get quite warm in the car. If it's a steady 40 degrees F with clouds and rain for days on end, it's quite chilly. Occasionally, we get a February where we don't see the sun for the entire month. People start jumping off bridges and tall buildings because it's so depressing. And cold frames become next to worthless.





Every year I get more of my beds off the ground onto tabletops. This year it was time to start getting my cold frames off the ground. I had a modified TT bed that I used for an experiment last year, that I decided to use.





It's 4x6 with a plastic cover similar to what Mel describes. But I insulated the box (sorry no pics of this). I put 1 inch pink foam on the bottom, then I covered the bottom and sides with that 1/4 inch bubble wrap that's sandwiched between aluminum foil. I bought a soil heating cable from my local hardware/nursery to fit the box. It has a built-in non-adjustable thermostat set for 70 degrees F. The cable gets taped to the bottom, and the thermostat is placed in the middle of the soil. I monitor a thermometer in the soil. This year in February, I had 4 nights that got to 24 degrees. The coldest the soil got was 58 degrees. I used a watt/hr meter to measure the power consumption. On average, the soil heater uses a little over 1 KW per day. For me, that's about 11 cents a day.

I planted the same seeds in the cold frame and modified SFG box on the same day. Lettuce, rads, spinach and carrots. We've had above average sunshine this year, and there is still a good size difference.










In the SFG bed, I also planted a bunch of misc. stuff: White onions, BS, brocolli, luffa, cabbage...... The way the stuff is growing, I'm thinking next year of doing some of my indoor seeding in this box. That way I won't have to harden off and transplant stuff. After I harvest the veggies in the cold frame, it's history!


Carrots in 25 days





White onions
(dang, I should have weeded before I took pics!)

LittleGardener wrote:
This is just AWESOME! - Thanks for sharing
as always, I have lots of questions:

1. WHAT did you use for the BOTTOM? of these "Heated T.T. gardens"
(preventing buckling/caving)

Two other threads that are applicable here:

Building table tops.
Building heated hoop houses.

2. How do you keep the wildlife such as DEER (etc) out?

After fighting the deer for six years with temporary fencing and silly ideas, I finally broke down this year and put up 6 foot fencing. I'm a slow learner!

3. Could a person compromise by starting something similar on a DECK?

Sure

4. About how much would it cost to build one of your "Heated T.T. gardens"?

They're just sfg boxes, so whatever your preferences for boxes are. The soil heating cable with thermostat is a little over $3/sf.

5. About how much would it cost to heat one, annually?

I have run a watt meter on them and it costs ~12¢ a day per box.