The owner of the farm I rent my land at is a Master Scrounger. Scrap steel, fiberglass molds, barely working engines, and barrels and tubs of all sizes lay around in somewhat organized disarray. Last year I helped him restack a few dozen 3’x6.5′ panels of tempered glass from a retail store front and have been waiting for this day ever since. My vision? A Ghetto Fabulous, monster sized, uber cheap cold frame. Step one started, as do many of my harebrained ideas, on Craigslist. I found a guy 5 miles from here with 100 bales of oat straw for $2.50 a bale so yesterday I motored over with my TDI Golf, trailer in tow, to load up. 17 bales fit oh so nicely, and with the ground frozen solid I was able to drive right up to the mini Hoop House.
Once the straw was on site and chucked over the fence it was time to start breaking ground. With the recent rains we lost over half the snow, but the resulting ice proved to an issue. The top 2″ of soil were not fun to break through, but below that was frost free. The plan was to scrape free the snow below the bales so that they rested on bare soil as much as possible.
I intended to lay out the bed on an East – West Axis, again to minimize shadowing, with the beds about 5.5′ wide and at least 15′ long. The width of the beds was determined by the length of the glass, the length of the beds is to avoid the shadow from the tree wind break located 30′ to the west, and I want to avoid the footprint of the planned 26×72 Hoop Structure to the East. Here is a shot about 25% through the job (30 minutes) with the layout taking shape:
You can see that there is alot of soil being moved. This is entirely on purpose for several reasons. A bale of straw is well over 12″ tall and casts a heck of a shadow in the low light angles of mid winter. So I sunk the south run of straw about 4″ into the soil. This, combined with the natural south slope of the plot makes for about a 5″ drop over the course of the cold frame. That is good, but I want better. For every 5 degrees of slope you gain about 125 miles of latitude to the south. So the soil from the excavation is piled into the beds, and once melted, will be “leveled” to give additional slope to the interior of the frames to maximize solar heat gain. Finally, the black soil will reduce the Albedo Effect of the white snow reflecting the heat to further increase internal temps and hasten the melting of the snow and frost in the frame.
Some of the glass no longer had their frames and were bowing more than I thought prudent. Luckily I had kept the 6′ bamboo poles I used for tomato stakes last year and they worked fantastic. Time on farm at this point was about an hour and change – much of that spent lumping glass which was stored about 100 yards away. I’ve had more fun than walking that far carrying 60# plates of glass over icy ground in winter winds… But it was worth it:
The straw cost $40, but will get used at least 4-5 more times (mulch for potatoes, then squash, then shredded for compost, then fed to worms, and their poop put into 2011’s cold frames🙂 ). I realize that few people will have 6-7 panels of tempered glass just laying around, but salvage windows, storm doors, etc are remarkably common if you keep your eyes open all year. Will it work? Well with one panel still to go on, no loose straw chinked into all the gaps, and the thermometer literally resting on frozen soil, the interior was registering 46 degrees as I laid the last panel on. Outside air temp was 21 with a steady 12 mph wind – easily enough to kill spinach and kale, let alone the lettuce I have in mind for this cold frame. Wind is the biggest issue in winter. If you can keep temps over 20 (25 better still) you can grow a remarkable amount of food if you shelter the plants.
This cold frame will hold 250-300 heads of Romaine. Early lettuce will command $4-6/lb, which means that my straw and $2 in seed will net a profit of several hundred dollars for my labor. More importantly my family will be in for fresh romaine in less than 3 months. Awesome. Next week I will build another (got 4 blisters today that need to heal), and may put a small one in the hoop house for kicks.