Hello Mikes,
Every once in awhile we get a freeze here as well, so this is the some advise based on the concensus of the local knowledgeables.
Wind is actually your friend! It keeps the air mixed and a frost becomes less likely at temps around 32. If it is wind chill you are concerned with...that affects only warm blooded animals. If you think about it, a rock for example is whatever ambient air temp is. They have no heat for the wind to suck out. In fact, the big, big, farms fly helicopters over the crops to generate wind to protect the crops..
Plastic is very bad. It holds condensation that then freezes. A heavy woven cloth is better. If you have to use plastic....don't let it touch the plants. If it does it will have no insulation value...combined with the condensation, like I said very bad.
If you can cover your favorite plants with a sheet and run water on the ground under the cover, that works too. Or keep a constant spray on the plants. Problem is if power fails and you lose the spray....
Anyway...this all just applies to temps near 32, dip much into the 20's and you need to add heat....which the water will do. Problem here is that with ineffiecient central heat ( as it isn't used much) brown outs are common and if the water stops..you're screwed.
If the banana has any size to it at all, a night watt bulb is useless. The heat will dissapate too quickly. A plain old sheet like Ester suggested will buy you 2 maybe three degrees and be more serviceable. If you have access to agricultural crop covers they are your best bet and even then you are only looking at maybe five degrees...which at 32 is a big gain.
