I don't see any reason why you couldn't just hose them off.

It's funny. I see those plant covers all the time, wrapped around foliage, several feet off the ground. The idea seems to be that if you put a blanket over a plant, it'll keep warm. It doesn't. Why? Because a plant doesn't generate any heat. (Which is why blankets keep us warm. We do.) If wrapped just around foliage, the temperature inside will be exactly the same as the temperature outside.

I also see them advertised as covering a plant on top of a big pot. (Without covering the pot, but sealed around the top edge of the pot.) Well, the pot will still freeze, with the roots inside. So that's not real smart. Though if the freeze is short, it might make it.

You need to cover the plant with something with a LOT of thermal mass inside the cover. Like the ground, or a wall. So if you drape them over a plant, you can anchor them around the edge on the ground. That way, the heat in the ground will rise up into the inside of the covering.

I just throw a large tarp over my frost-sensitive plants, and anchor it on the ground around the edge. If it's a hard freeze, I throw a sleeping bag over them first. That makes for better insulation, and just holds the ground heat in better. But the rule for freeze protection is *trap the heat coming up from the ground*.

Our cold temps. have not been extreme, but cold enough to do damage to tender plants. I slept better with them covered. :-)) I do anchor them to the ground.
If not anchored I also doubt they would help much. The potted plants seem to do fine in the garage. I'll put the hose to the covers today before the next front hits.
thanks for the information.

Yep, that's right.

BTW, I have learned that there ARE plants that generate their own heat. Called exothermic plants. These are mainly those stinky plants that trap insects. I guess if you wrap one of them up (but I think it's the flower that produces the heat, so they have to be flowering), they'll keep themselves warm. Warm-blooded plants!