February 2, 2017

Good morning, knock on wood the extra early toms are coming right along. They have already made it through an 18 degree morning. Granted they were covered with quilts.

I have remote temperature sensors under two of the temporary greenhouse and one just in the garden. These are giving me some real good data.

I felt that the greenhouse with the triple cover would be warm; I had no idea as to how much so.

On a recent 60 degree day my regular greenhouse with Ag 70 over film was giving a reading in the 70’s, while the tom bed with the low hoops covered with 2 layers of Ag 19 along with higher hoops with film covered with Ag 70 was pushing 90. The film was rolled back along with the Ag 70. Once the bed had cooled the low hoops with the double layer of Ag 19 registered a temperature in the 70’s. This is the first time I have noted the temperature under Ag 19 in the low hoop configuration. This was the same temperature as my normal greenhouse. The difference is at night; without the film covered with the Ag 70 a good portion of this solar gain is lost.

This reminds me of something Eliot Coleman, a grower on the Maine coast, mentioned: that beds that are covered with fabric inside a high tunnel makes for a warmer bed than one that is not covered with fabric.

The experiment with the three different configurations of film covered beds really enlightened me as to the placement of the fabric. The fabric has to go on the outside of the film. This has big effects as to what happens during the night and then during the day. At night the fabric slows the heat loss that would occur with the film being exposed. Plastic is a better conductor of heat coming in and heat going out of the enclosure. The fabric does conduct heat but to a much less degree. The fabric during the day tempers the amount of warmth generated inside the enclosure.

One thing I was hoping to see in my normal greenhouse is the heating of the soil. Observations indicate that there is some but I have no way to determine to what extent. I keep thinking of purchasing a thermometer to do this, maybe for next year’s winter season.

This all may sound rather tedious but it fascinates me how easy it is to harvest day time heat to protect plants at night. Also it is amazing to see what results can be achieved by just how these components are arranged.

As the days going forward start hitting the 70’s the film will be needed to be rolled back and removed. It has been a good year to test how well this works. I have been very pleased and ready to give it another whirl next year.

This week I harvested chard, kale, spinach, Asian greens, green onions, beet greens and from storage sun chokes and sweet potatoes. Please email for quantities and availability,