It depends on what you are growing.
Some orchids bloom as a response to changing of the photoperiod, others depend on the diurnal temperature variation and others rely on both.

I just read where someone drops the light time to 12-13 hours for the fall, then ups it again for winter.

I have:

Dendrobium
Oncidiums
Burrgerria
Wilsonaria
Barkerari
Cymbidium
Encyclia
Maxelleria
Zygopetulum
Phiaus
Reed Steam Epidendrum
Cattleya
Phal
Renenthera

Quite the array.

Barbara, most orchids in cultivation come from the tropics and sub tropics.

Length of "Day" here at latitude 33 South

Mid winter just short of 10 hours sunshine

Mid summer about 14 hours sunshine.

Sun in mid winter weaker because it is warming the frozen north but nearly every orchid i own has at least 50% shade-cloth cover. It might be as Wetfeet says, Depends....

Red stem epidendrums need high light all year otherwise they grow lank.

You need advice from the the under light guru, Howard.

I understand that Catts that have alot of C. labiata in their parentage require the short day treatment. I'm not aware of other orchids that require short days to initiate buds, but I don't know everything. Poinsetias do, but that's off topic. msflintlock

Thanks, guys!!!!

When growing indoors and using cfl you are usually using duration and consistency to stand in for intensity. In most cases you have nowhere to go as regards a downward adjustment in the fall/winter. A truly daylength dependent bloomer like the catt mentioned or the more well known non-orchid flowering houseplants will not reliably bloom indoors. Even if you did adjust the light times stray light from other sources would inevitably cause an issue. Christmas Cactus will set buds in the presence of a nightly temp drop even if daylength is unregulated. I think Poinsettia are more demanding in this respect. I would leave the light time in an indoor garden unchanged and individually deal with any daylength dependent bloomers on an individual basis. Often a period of time out of doors at the beginning of Fall, and by that I don't mean shuttling back and forth indoors and out, but left outdoors day and night until buds are set, will be the best way to handle both orchid and non-orchid daylength dependent bloomers.

H

Awesome! Thank you, Howard!