Many of you read my recent blog post “I Am A Farmer” (click here to read), in which I introduced you to my fabulous cold-frame that Matt built for me. Its been a little over a month since then, so I think its time for an update.
First off, I have gotten a couple of questions more than once, so I’ll address them here:
In reality, the only real difference is that my cold-frame isn’t heated. There are probably some greenhouse purists that could explain some more detailed differences, but the main diffference is that a greenhouse is generally heated and larger.
2) How does it work/what does it do?
My cold-frame is built on an angle and faces the sun for the majorety of the day. It is covered in clear but cloudy plastic, and lets in about as much sun as the plastic of a milk jug would let though. (That’s why winter sowing like I outlined in this post worked well too!) When sunlight shines on the face of the frame, it gets trapped by the humid environment and the plastic which partially insulates it. That heat stays inside and keeps moisture inside as well, allowing the seedlings inside to germinate. The shelter from wind alone keeps the temp higher than outside the structure, but the sunlight adds a lot of heat when we have a clear day.
The temperature in the frame is consistently warmer than outside, and I am hoping to get some quantifiable data soon (for my own curiosity mainly). The exception to this was on the windiest day I have seen in a long time, which was about a week or two ago. That leads me to the next point…
The frame is doing well so far, but I have had to get a bit more creative/intentional with how to keep the back side of the plastic in place. The back, or flat part of the frame is where I enter and exit, so it must be free and unattached. However, I was not too happy to discover that the entire back side of the frame was quite literally flapping in the breeze when I went out to water one morning. A huge wind-storm for which my wooden planks were no match had drastically cooled the internal temp and dried out nearly half of my starts. Fortunately, nothing had germinated yet, so no seedlings were lost. I re-stapled the plastic to one side and Matt added a heavier hold-down to one side of the “door”, which has been working very well ever since.
When we get snow, I brush it off with snow brush meant for clearing a windsheald of a car. This ensures that the sun can get through to the inside of the frame, but also helps the plastic stay taught. I find that the wetter, heavier snow begins to stretch the plastic if not removed quickly. This is not a difficult task, and has not caused me any problems thus far.
Moisture retention in the frame is great so far, so I only water every other day (and that is not always necessary, though I check anyway to be safe). Most of my starts still look like nothing more than hopeful bays of soil, but this week I was so very excited to find some green! Now that a few sprouts are presenting, it is much more important that I retain a high enough temperature for their survival inside the frame. These little guys motivate me while I water a bunch of brown for now; aren’t they great?
One other note:
I did a day-long experiment last week on a very clear and sunny day, and found that the cold frame is getting five and a half hours of full sun, and seven and a half hours of partial to full sun in its current location. This could change as the days lengthen, but I am happy with those numbers for now 🙂