My outdoor friend uses a patio heater which has a 18†square base with a 7’ tall column and the top has a wide coolie hat type of cover that reflects heat downward. She uses a 20lb bbq propane bottle and set to low lasts about 2 weeks during the 6-7 hour use at night. Has no cover so the heat all goes up eventually. I think it was $160.00 on sale last year. She said it keeps a 30 degree night off of her plants. When I was a kid, we had to light smudge pots in the orange groves to keep frost off the fruit but there had to be hundreds of them and they were diesel fueled and smelly...but they worked. Yeah, maybe too extreme