I have a large hoophouse that I seal up and use like a greenhouse during the winter. Because it has only plastic sheeting for walls it doesn't hang on to any heat so it is hard to keep "tropical". One surprising thing I've tried is to build another smaller greenhouse inside the larger greenhouse, sort of a tent made out of this very thin clear plastic I had on hand. By placing the tiny electric space heater inside that tent I can keep those plants very warm. So I try to keep the large area just above freezing and never have to worry about the small area. You might be able to build such a temporary tent out of thin plastic (I just used ropes and clothespins to build mine) and put the heater inside it, instead of heating the entire garage.

I don't think you will find a true citrus which is hardy enough to survive zone 7 low temps. Poncirus trifoliata will survive and make fruit. It is a first cousin to true citrus but the fruit is bitter and all seeds. Sasumas/Mandarins were killed back on the Gulf coast during the January 1982 freeze and many otheres were killed during the March 1993 snowstorm of the century. In Alabama, we had a very mild winter of 2005-2006 and one might have survived it. Temps only went below 20 once or twice in suburban Birmingham.

Herman, thanks for the update. It’s great to see fruit already. How large are the Conestoga 026 Segentrange and Poncirus Plus fruit? They look similar to PT…….or are they larger…….photos can be hard to judge. Great to hear 5* Citrumelo has some sweetness. Fruit ripens around Thanksgiving……but the size is clearly larger than PT…….a nice selection. Getting fruit in 3 years is very fast. I gave my brother who lives in Fairfax, VA a seed grown Citrumelo 12 years ago and it still hasn’t bloomed! Keep the updates coming.

Jenny, that’s very useful, understand how the hardiness zones are calculated. Since my area has hot humid summers, I’m gonna guess it’s probably a lot like Virginia or the Carolinas? Crazy pest and mold problems here, but when things grow they grow like crazy. The weeds in the summer are like nothing I’ve ever seen. Yuzu was the first citrus people recommended for this area. Mikan (mandarins) were recommended too. The resprouting is kind of neat, and at least before the moles showed up, they had very extensive root systems, which should help with regrowth. I’m not expecting much or any fruit though, as there’s no leaves to support them, and all has to be regrown in one season. Not sure how useful that is. Thanks Cory. The last time I tried grafting I cut my thumb open in the grafts never made it anyway! Pon, I agree with you, it’s nice to use the passive heat systems. I’m still interested to experiment with some ideas. The typhoons really make it tricky here though, as things being blown away can be a bit dangerous. I don’t miss low temperatures like that anymore. I would have no problem moving to an even warmer area that I’m in now.