In the natural habitat, the day length for all the unifoliate, large-flowered Cattleyas is not less than about 11.5 hours or more than 12.5 hours. With LED lighting, which is constant, as compared to your windows where the light intensity is rising and falling during the day, you want an intensity that is about half the peak that you had at the windows but carry this intensity through the entire day. This gives the same daily light integral.
I have been on a deep dive into the winter rest of the unifoliate, large-flowered Cattleyas and I purchased the Baker culture sheets for these species. It is interesting and fun to try and customize the temperature, and particularly the fertigation, characteristics of the in situ species.
For some, the temperature drop in winter is of some importance. For others, it isn't the temperature change but the change in the rain frequency that triggers a growth. I think it is OK if I copy a small section from the warscewiczii document here.
"One grower reports that temperatures must be less than 62F (17C) when new growths are 1/4-3/4 in. (0.6-1.8 cm) long for bud formation to be induced. It may eventually be found that dry periods initiate new growths, cool
temperatures initiate flowering, and that plants can flower twice a year
if these conditions are met. This is our speculation, it has not yet been determined.
Research with cultivated plants indicated that flower buds of Cattleya warscewiczii were initiated in late winter as days become longer and night temperatures drop to 55F (13C). Flower buds did not form if plants were
temperatures drop to 55F (13C). Flower buds did not form if plants were grown with continuously long 16 hour days or at continuously warm night temperatures of 65F (18C)."
