Short day length for photoperiod sensitive Catts
 

Some members of the Cattleya alliance require shorter day length to initiate bud growth up the sheath. Since I am growing indoors under lights in a basement plant room I have control over day length and temperature. What do you think the period of time (in weeks or months) of short days needs to be to initiate the bud growth for these photoperiod sensitive plants?

Take a look here:

Greenhouse Light Levels

Thank you much. That is similar to what I have been doing. However, because I also have seedlings that would like a greater period of time at 14 hours or so, I was looking to minimize the time spent at 11 hours. My Phalaenopsis spike primarily because of cooling at the time I am shortening the day length. Because I am in Minnesota my cooling period (with windows open) is September and October and my Phalaenopsis are all in spike now. It would be great if 12 hours in September and 11 hours in October, followed by an increase in light back to 14 hours in November (and for the rest of the year until the next August) would trigger the short day plants into bloom. However, if these plants need a gradual decrease and then increase in light as occurs with the natural seasons then this won't work. I am trying to fool Mother Nature.