I saved persimmon with a tarp and 1500 watt heater against 24F. This is a pretty big tree, about 7ft wide and tall. So it takes a big tarp. Two nearby unprotected trees lost all fruit and leaves.

I saved grapes from the same freeze by covering and heat.

Saved 15 inch tall sweetcorn by heavy covering without heat. A very few leaves were frost marked. Was covered with cardboard, blankets, and refectix insulation, three layers overhead and two on the sides. It would have taken very heavy and many layers frost blanket to save this crop from 24F.

Wrapped one jujube graft breaking bud with three layers of row cover. It was killed by ~28F and hasn't sprouted back. Other jujube grafts covered with heavy black barrels survived 28F but not 24F later on. It took blankets and another layer to save those.

I think the frost blanket by itself is effective only on low growing veggies with warm soil close at hand. I think fruit trees are too high to benefit much from frost blanket.

An air tight covering has usually worked for me with sufficient heat inside. 750-1500 watts for medium size tree and 100-250 watts on a small tree.

I saved my figs a few nights ago with tarps and no frame. You need to have the covering spread out below to capture rising heat from the ground. Because I didn't use a frame I lost anything touching the tarps. Uncovered figs a few yards away (nursery trees) were fried.

You both have pretty much confirmed my suspicions, while also providing the evidence that it is possible. Now I'm not sure if I will continue to try covering my peach and apricot trees, unless maybe the temp is not expected to go much below the critical point. Maybe I'll try a tarp where I use the heater method next time.

Air movement is used to protect orange trees from moderately low temperatures. My mother believed that old-fashioned Christmas lights with no cover saved her apricots some years.