Frost - not sure

Went out round the garden this morning to check if there had been a frost, but don't think so. It was pretty chilly though. Anyway, this happens to be the only picture I've taken today. I am really quite pleased with this dahlia, it's the first one I've had. And in a couple of weeks we are going down to a nursery outside St Albans that specialises in dahlias, so will be interested to see if any of theirs in their celebration garden are still flowering. I do hope so.