Vicki
Girls With Guns Member
Harvesting... The vegetable must be fully thawed and warmed prior to harvest. If you harvest frozen plants they will be wilted. These are for plants under a single layer of 19 weight row cover. The temp listed is the temp in the greenhouse; not outside.
So how cold is too cold? Single digits leave everything wilted and black. If you had the inclination you could double or triple cover and the hardiest plants would make it thru. But these are temps of deep winter and no Joke.
The most cold hardy I found was Lettuce. It can be expected to survive 10F. Lettuce will grow on the warmer days when the nights are in the upper 20's but will take several days to recover and return to growth if the temps dip into the teens. Prolonged temps in the teens will make it have cell damage and slight texture issues. But will be fine tasting and sweet. It's at least as good as the California imports.
15F Radishes and carrots will be fine for harvest, The tops will be gone. They will not grow and should be harvested before a real warm up or they will go to seed.
20F Cabbage will be fine tasting and sweet.
25F The rest of the Brassicas, turnips, rutabagas, beets and chard, and Chinese greens.
27F All frost hardy veggies will recover daily and continue to grow. Tho several days of cold will stunt the growth.
38F Solicitous are frost sensitive crops and will be stunted but will survive. (tomatoes, peppers, eggplant, ect.)
42F Cucurbit are very cold sensitive and will suffer stunting if the temps drop this low but will survive. (squash, zucchini, pumpkin)
55F Rapid growth for all garden plants is possible in a greenhouse. Temperature in not a significant limiting factor.
One thing to realize is relative humidity has a large bearing on the low temperature inside the greenhouse. Keep things moist if possible. If cold weather is in the forecast water the plants well and cover. The added water contains a lot of latent heat. A simple hose down can raise the temp of a green house well above the danger zone.
Excellent information. Thank you! I managed to get the first layer of new film on the greenhouse today with alittle help and the second layer goes on tomorrow. I'm liking the new film alot. Good deal. There was a small hole in the one piece and I think I'm going to write them to tell them that but I taped it up and all is well. 46 degrees tonight.