After two sharp frosts most of my dahlias are done for. But these tree dahlias, pictured this morning, are looking as fresh as a daisy. The one with the pale green leaves in the foreground is the Dahlia Imperialis. This is the tallest of the dahlias and will continue growing, frost or no frost, until Christmas. It has only once produced flowers outdoors in my garden, which was on December 16th in 2006, after the longest, hottest, summer we’ve had this century. But the others, Excelsa and Tenuicaulis, have been flowering freely all summer, and although their flowers are insignificant compared with the hybrid dahlias (these are species) something is better than nothing at this time of year.