Coleus are one of the first things I know of to succumb to frost, especially the tips, and they don't recover. We're supposed to get 38 degrees here Wed. nite. Frustrating since the 10-day shows 3 nights of questionable temps, then back to normal, around 45-50 for lows. Sheesh! Since there is no margin for error with coleus, I plan to get all of my cuts made and in the house by Wed to be safe. I don't know the exact temp where fatality occurs, so anything below 40 is the line I draw.