Heading home today from the state of Florida. I have told the Grands that it will probably be the last trip down here till Late fall. Gardening in St. Louis occupies me 24/7 during growing season.
This week in it was very cold here. I left very cold in St. Louis. In fact it was extremely cold. I believe this January is the coldest in at least 10 years.
We have a Green house that is 48 X 24. It is a hoop house with double poly. A small fan keeps it inflated with an insulating layer of air. We found a small thermometer that is battery operated at Walmart. It records the high, low temps and the current Temp. It also records the high, low and current reading of humidity. Each day twice a day we remove the battery to reset it.
We have found when the temps are at 20 to 32 degrees outside, the double poly only keeps the temps inside about 10 degrees difference through the night. When the temps dropped to 0 and the two days we had -12 and a week of -'s the temps inside never dropped lower than 18. During the day if it is bright sunshine outside the temps can reach 100 degrees inside. Wind does not seem to be a factor in the temps inside. On an very cold cloudy day when it is preparing for snow the temp can be counted on to be at least 50 degrees during the day with no auxiliary heat source. I believe the stored heat in the earth keeps the temps up during the night. The ground inside the green house never freezes. We have had at least a 1/4 inch thick layer of ice on the inside of the green house plastic due to the humidity accumulating.
Growing prolifically in the empty beds are those hated winter weeds, Henbit and Chickweed. We don't mind the chickweed in the green house because we pull some every day to feed to the 6 Hens we have. They have done quite well in this cold weather. Producing 4-5 eggs almost every day. The Henbit though, geepers, does anyone know of a natural eradication of either one of these plants. Henbit is a perennial pain in the back side. Chickweed gets out of hand so quickly and even though it is an annual it seeds and grows in all weather. The only time I have seen it thwarted is in hot and dry, but those seeds stay sleeping till more advantageous living conditions come around.
I haven't access to pictures till I return home. Or I would post some now.
We have a smaller hoop house inside the large green house. It is 9X16. It is not a double poly. It is on a 2 ft high base that is insulated. The base walls are constructed with out door plywood, which is painted with enamel outdoor paint. There is batt insulation in the walls. We used a heavy gauge plastic to cover the hoops with. The end walls are a baffled plastic. We made it removable and put screens on the inside so we will have an environment that would be bug-less as it can be. Also so we would have summer ventilation. There is a fan in the north end to help pull in cool air.
We have been keeping my over flow of house plants in the small house. Things like Hibiscuses, crotons and avocado trees. There is a 6 ft row of 2 feet high rosemary which is over 6 years old and still growing fabulously (I have had trouble with powdery mildew on it. We keep a fan blowing on it constantly.) If anyone has a cure or preventative let me know. I tried spraying baking soda water on some rosemary that I had outside this summer and it turned black within 24 hours and died. (I use baking soda to prevent black spot and powdery mildew on my roses.)
We are using space heaters to heat the small green house. I don't know if it is economical but we had no other planned source of heat. We didn't even now if the little house inside the big house would be able to retain enough heat to have the house plants in. This is our first year with the inner house. We will have another heating set up by next year. It was a rush job at the end of last year.
The rosemary that is 6 years old has been previously only covered with heavy covers and three lamps underneath to keep the area from freezing. being our last few winters were on the warmish side it suffice to keep it alive. When spring came it recuperated toute suite. This year in the new inner green house it is acting like it is in the Mediterranean. Growing fabulously.
I planted some tricolor sage in the smaller house (I haven't been able to winter it over in the st. Louis area.) So far it is doing great, hope I will be able to take cuttings from it when I get home this week. There is also a plant of Bergarten sage in there and I will be treated to some beautiful sage blooms soon.
Have to run to catch a plane. Hope to return with pictures tomorrow.