Experts and BHG readers answer.
Can I save my frozen dinner-plate dahlia?
The extent of damage to your dahlia depends on how cold it got, and for what length of time. If the plant was nipped by frost, it will probably come back; but if it was completely frozen, it may be too late to save it. If the roots didn’t freeze, the dahlia should be able to grow from the roots. At this point, the best option is to wait and see if it resprouts. In the future, wait until all danger of frost has passed to set out your dahlia, or be prepared to protect it from frost on chilly nights.