Soil frozen in greenhouse, water with warm water?

Should I water my plants with warm water to unfreeze the soil? ...or will this shock them and kill them?

I reckon it got below 20 last night in the greenhouse... I'm incredibly impressed that I may have only lost one small avocado tree (it may actually bounce back), but I'm afraid I'll lose more if they go through another night of the same.

What do you think? Something needs to be done soon so... if you can, respond quickly! Thank you so much.

If it is still freezing, you do not want to put warm water on them.

Warm water will lose its heat so fast that it will freeze long before it gets to 32*
Kids that want to go sledding on the driveway know that they need to put hot water on it for a quick/hard freeze.

Also, if you expect more freezing tonight, you probably don't really want wet soil.
That would just encourage it to freeze deeper.

Get some heat in there, or some kind of protection for the plants.
It's a long ways to spring thaw.

Okay. Thank you. I'd read somewhere that the process of unfreezing is really what causes lots of the damage from freezing. So... I'm wondering, if I do heat up the greenhouse, does this pose a risk if soils and plants start to thaw?

What I did the day before yesterday was put rocks in a fire and put the hot rocks in a terracotta pot in the greenhouse. I've also lit incense in the greenhouse to cause mini-climate-change by putting carbon into the air (?).

Not sure... just trying things. Thank you for your help John.

In this scenario, the subtleties of freezing water probably don't mean much. If you are determined to keep adding water until the soil thaws, then warm water will transfer more heat and warm the soil faster. Whether or not that is a good idea for your plants is debatable and probably depends on the plants. I certainly wouldn't use water warmer than 70 degrees F.

If you have only a small amount of water, then evaporation from water heated to 140F or higher will cause a reduction in volume, allowing the remaining liquid water to freeze more quickly, but the water won't magically freeze at above-freezing temperatures and in the enclosed environment of your greenhouse, all of that heat is ultimately going toward raising the temperature of the greenhouse as a whole. If water is the best means that you have of adding heat to the greenhouse, then go for it.

It looks like I might only lose two or three avocado trees (which should have been inside the house). That's after the soil was frozen for two days. I'm amazing at how well things do in that greenhouse.

I also might have lost a couple calendula in the ground outside. But both the calendula and the avocados may surprise me...

I think the hugel that I built inside my greenhouse (and it's small, 6x8) has really helped. I can recommend that. I think lots of heat and humidity come off that hugel.