A couple years back a family friend dropped by w/a flat bed trailer carying pieces of an old bent up greenhouse/cold frame. The dimensions were impressive at 35 x 150 but ultimately at the time it was useless as there were entire sections rendered unusable due to a snow/ice collapse and the lack of anchor posts and pearlings, as such it got drug over next to the neighbors fence and lost in the myriad of weeds and briars where it became a hinderance every year at bushhoging time.
I had been eyeing some small frames that a former tobacco farming associate had on hand which had been used to make floating tobacco beds for raising seedlings, but I was never able to talk him down enough in price to actually buy the frames; one night while lamenting my lack of a hot bed (despite the fact I have a greenhouse, this project is more for producing seedlings for use on the farm as well as for rooting cuttings in the winter, and I figure if things ever get "that bad" it will be easier to find a piece of scrap plastic to cover this and produce seedlings than to find a piece of 4 year/6 mill plastic to cover a greenhouse) that I hit upon a fantastic idea.....cut the frame down to size, bend it to a usable shape, stick it in the ground and save myself a few hundred dollars.......
So, this past week I commited and drug some pieces of frame over to the Peasant barn where I cut the half sections of hoop in half and then used a wooden post and corner stone in the barn to bend the pipe (suprisingly malliable) to roughly the same size. It just so happened that each hoop also had a female connection on either side which I cut off about 3 feet below the connection for anchoring to the ground. This gave me about 10 hoops (theres still much more pipe but I don't currently need it all) of which I had enough females for four usuable pieces.
I drove the connectors into the ground (spaced in four foot intervals. 12 foot of bed total) and squared them up and attached the hoops to the connectors. I then scoured over the creek bed to find a few flat sandstones to use for walls for a raised bed on either side. After all of this was in place I excavated 8-10 inches inside the frame for a "pit" feature and piled the dirt up in birms to either side of the rock walls and on the end of the frames.
The next step is to burn a hot fire in the pit to kill out any weed seeds and add some potash to the soil, after this the pit will be filled with 12 inches of uncomposted chicken litter with a layer of woodash overtop of it and about 5-6 inches of worm compost overtop of that, it will be moistened down so that the manure composts producing heat and covered over with plastic (which will be attached to heavy rough cut 2 x 6 pieces by wrapping it around a couple times and stapling down using batton tape, giving the ability to raise and lower the plastic on either side or remove it) a week or two later it will be seeded with tomatoes, peppers, eggplants, and tobacco.
This is essentially the same method used for a few hundred years to produce tobacco and tomato seedlings locally, minus the plastic of course; brush piles used to be used for frost protection and then remay material at a later date.
I'll take pictures as the season and project progresses as well, but thought those of you who might have access to some bent up frames or even metal conduit via hardware supply stores might also want to experiment as such. Much cheaper and easier to maintain than a greenhouse and if I had it to do over again I'd likely just build two or three of these to a good size.