Sounds like a lot of poorly composted soil amendments. You don't say where you are, but I'm guessing it's not Death Valley.

How long will it last? Probably weeks.

If you bore cooling holes around each of the plants, you might be able to save them.

Thanks. I’m in Southern California (10a). Any specifics on the cooling holes? I’m guessing just a ring of holes around each plant, as deep as possible?

Well, you want to make the holes as close to the plants as possible, BUT, you don't want to hurt the roots. If you stay further out than, say, twice the dripline, your roots will probably be safe.

The frustrating thing about this is that you'd like to dump water in the holes to cool them off, but that's just going to speed up the decomposition, and heat things up. Also, one has to assume that aerating the pile (which the holes would do) will do the same thing. So the fix is by no means a clean one. Got a lot of ice?

I've never heard of anyone trying to STOP composting, so you're breaking new ground!

Got it, thanks. Frustrating indeed. I’ve never done sheet layering in a bed before. Lesson learned. Next time I’ll wait to plant or compost separately, as I usually do.