low temp for tectorum seedlings?

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I was dismayed today to find my tectorum-bearded hybrid seedlings seem to have been killed by cold.  the temps have only dropped to about 30 and only for a an hour or two right before sunrise.  the straight bearded seedlings are fine.  i never in a million years would have thought the tectorum were too tender.  i'm going to be soooo upset if they are dead.  but the foliage looks completely zapped.