Hello friends,
Last year, my citrus trees barely survived their first winter in north Texas. Over watering in December just about killed my moro orange, and a soap/neem oil mix killed the new growth on everything else. Then, I pulled down the green house after an 85 degree day, only to have a freeze 5 days later. I put plastic over the trees, so they survived, but all the leaves touching the plastic died.
Fortunately, I had just discovered the trees really liked a 30-10-10 fertilizer DW had in the gardening cabinet (Rhododendron food). I consciously decided to pay less attention to the trees, stopped trying to kill bugs with chemicals, and cut watering back to once a week until the heat of summer. Everything recovered.
Over the last month, I've build my second greenhouse. The 'plant' area is about the same size, but this version isn't connected to the house. Last year, the green house had a plastic-enclosed hallway to the house and an open sliding glass door kept the thing at about 50. This was a very bad idea. We spend about $200 extra on heating and the house was chilly all winter.
This year, the 'Nov-April' greenhouse is independent of the main house. Now, it is a 'cold house'. I just want things to stay above freezing. Heat is provided by 6 or 7 strings of 5 watt Christmas lights run through the branches. I've buried the pots to let the ground warm the roots (last year, they were up on stands and the Christmas lights were wrapped around the pots).
The greenhouse seems to stay about 10 degrees above the outside temp, so it stays above freezing until the outside temp drops below 22 degrees. That is about as cold as it gets unless an artic front blows through and drops temps to 5-10 degrees for a day or two. This has already happened once. To keep the plants above freezing, i covered everything with plastic or old sheets. Under cover, the temperature stayed around 50 degrees. The general air temp only dropped to 30.
The greenhouse covering is 4 mil plastic purchased at Home Depot. Last year, I used 6 mil plastic. The 6 mil plastic was too perforated to be used a second time, so it might have been over-kill. Given I spent so much on heat last year, heating by Christmas lights seems a wonderful alternative. They are on a thermostat and only turn on when the temp drops below 50 degrees.
Below is the temperature performance of the greenhouse/cold-house. We are in north Texas and get plenty of sun during the winter. The sun will raise the temp 30 degrees or more above outside temps if the door is kept shut, so even when the outside is 10 degrees (about as cold as it gets), the plants are well above freezing without any extra heating.
outside
inside
zzzzz
