SEATTLE — Seattle gardening expert Ciscoe Morris says that keeping dahlias looking good is a matter of picking flowers that are past their prime. ‘If you don’t get rid of the spent flowers, they go, ‘I’ve done my job, I’ve reproduced, I don’t have to do anything but enjoy the sunshine, get a good tan and eat a little fertilizer.’ They stop bloomin!’ Ciscoe said.  He advises cutting any faded blooms back down to their stem, and leaving the side buds, which will still flower, especially if the plant isn’t wasting energy supporting old blooms.