Ellen, I'm not sure what you mean by "too hot".

All seeds have an optimum temp @ which they'll sprout. If the soil temp is out of range, (too hot or too cold) germination will be inhibited until a more hospitable range is reached.

However, if by "too hot" you mean that the seeds permanently lose viability, I'm not sure. I guess it would be possible... Boil seeds for an hour, I imagine they'd be ruined. :-) But @ the temps our seeds are exposed to, I doubt it. This is conjecture on my part though.

Karen

I've been wondering about this one as well. These last few weeks have been really warm here in St. Louis. Finally back to normal temps for spring. Anxious for my lavender seeds to all sprout.

~stlgirl

Seeds certainly lose viability in a hot compost bin. I think 140 degrees is supposed to kill weed seeds. The length of time the seeds are exposed to the heat also effects the loss of viability. Cycles of hot-cold-hot-cold will also effect germination rates. I don't think our containers hit 140 very often, but this year might have been an exception. What do the summer sowers say about seeds and really hot temps?

Martha