IMO, you are probably over doing it! I live in Charleston near the beach and our temps will be in the upper 20's. Earlier this year we had temps in the upper teens that lasted for over 12 hours. This is unusual in our area as I have resided in the area for over thirty years and have only seen temps in the teens on a few occasions. When the temps dropped earlier this year many citrus trees were defoliated from the cold. However, the majority regained their foliage by late Spring and are doing well.

Oh god, Seagel - you CANNOT use plastic because if it's sunny and even 59, it can heat up to 90+ in there during the day and the plant will cook. I've lost stuff that I used plastic on. Better to get something called "Frost Cloth". You can leave that on all winter if you want....I do....

MDog

Or you can keep using the same plastic but add a little door which will be opened by a thermostat bellow -- same as the one used on the old VW bug air-cool engine. When it's hot in there the bellow expanded and pushed open the door, and you can use the little "green house" all year :)

Sapote

Thanks guys.

I've only left the "temp green house" on after sunset and before sunrise (when night time temps get below 40) for safe measure. Gotta love the sudden temp drops of Central FL.