Hi Rick,

Day length is a function of your Latitude, so it varies continuously with where you are on the map and where you are on the calendar. And plants in nature deal with that. I split the 24-hour day into thirds, and have my timers set for 16 hours of light and 8 hours of darkness. That seems to work OK for the plants I grow, and it suits my personal preferences, so I haven't run any experiments with different timer settings.

Many plants do respond to the photoperiod differently in Nature during their life cycle (photoperiod can induce or delay flowering in some) , so it would make sense to do some research and/or experimentation on the preferences of your delphiniums.

ZM

My lights are on for 16 hour a day usually. I'm beginning to believe that for some things it might be better to cut back the hours. I grow a fair amount of cold season greens (mizuna, bok choy, kale etc.) in cold frames and tunnels that are started indoors. I have not yet run an experiment but it seems to me there is a tendency for plants to run to flowering prematurely. I plant on testing this theory by cutting back the lower shelves to 10 hour a day. On the other hand warm season indoor starts seem to do better with 16 to 19 hour per day.