This weekend I transplanted some salad greens out to the hoop house. I started them from seeds last month in the warmth of my basement underneath some shop lights and now I've sent them outside to grow up and become a salad.
They've been outside a few days and even though it went down to 29 degrees last night, they're still doing fine. The 10 day forecast is showing warmer weather so these little guys won't have to endure freezing temperatures again at least for a little while.
Now if I was a full time garden blogger and had the time in the world to run all kinds of experiments the first thing I would do is add some sort of thermal mass to the raised bed. Perhaps I'd try a really large stone (like a 30 pounder) or a few 5 gallon buckets. I'd partially bury them on the North side of the bed where they could absorb the rays of the sun all day long. Then at night the stored heat would help to slightly raise the temperature inside the hoop house.
Another thing I'd would like to do is move the wireless sensor on my Weather Station into the hoop house to see how cold it gets in there at night and compare it to the outside temperature. Without a thermal mass though the temperature is probably the same. But at least the plants are protected from the wind so the hoop house is doing it's job.
Since the bed is already full of salad greens and a few root seeds that I sowed over the weekend, the thermal mass idea is definitely not going to happen. But there's a good chance I'll get around to moving the sensor to get some temperature readings. Wish me luck!