Of all the methods I've used this year - so far the easiest, fastest, and I think the best overall (temperature wise) is the lights. They might even be cheaper in the long run since I can use them year after year with only the cost to power them.
I am only trying them on two of my basjoo, the largest and one up front (which I'll probably mulch eventually and remove the lights). But the one in the back is my tallest and I wanted to preserve it. Frost hasn't hit it bad yet - it's next to the house. But we've been 32, 31, and 29 the last three nights. Bad frost yesterday and today - took my whole front yard out. Calling for 33 tonight with more frost.
Lights come on at 38F and the largest lights burn the warmest - but not too hot (I can hold it in my hand). Smallest lights are easier to cover a larger area and together make a nice amount of heat themselves. Last night at 29F the trunk of this banana was a nice 43F (with just a single strand of lights - there are three now). So even on our coldest night of around 16F in January that should mean a lot of protection, especially if I throw the frost blanket over it too.
I removed the
cage from around the larger p-stem - I think the lights will work a lot better than hay.