I have a 5 ft. upright rosemary that is several years old but this winter we got to minus 9 degrees one night & the leaves on the rosemary feel dry & crumble... could the cold have killed it? I also have prostrate rosemary on a narrow bed on top of a 4 ft. wall & finally got them to grow over & cascade down the wall ... now this past winter I fear may have killed them also! Should I just leave them both alone to see if they will revive/come up from the roots ... or are they a lost cause & I need to pull them? How long should I give them to green up before I call it 'dead'?! I didn't realize they could not take temps. like we got that one night here!