Day length / rest period

[protium]

Hello all, I am trying to understand how the length of day under artificial lighting affects orchids.

From what I have been reading I understand some orchids need a rest period during the winter in which they are watered and fertilized less often.

If the orchids were kept under artificial conditions in which the hours of light, temperature, humidity etc.. didn't change over the course of the year would they still need a rest period?

I understand that the orchids wouldn't flower under these conditions.

Assuming one can control the hours of light received and the day and night temperature; Is it possible to keep an orchid in vegetative growth and then force it to flower buy changing light and temperature?

[King_of_orchid_growing:)]

I highly advise against doing this for plants that go dormant/deciduous during the winter. Over time you will see the negative effects. It may not be right away, but you'll definitely wonder what happened. I especially discourage this experiment if you're going to do it on rare plants.

If you're experimenting, try this on plants you're very confident you'll find very easily no matter what. A controlled experiment also means you need to get more than one of the same kind (species or hybrid). I'd say you'd have to get at least 10, preferably more of the same hybrid/species, that are roughly the same age, similar in size, and the same number of growths per plant. All the more reason to find extremely common plants.

You need to set up controls and an experimental variable.

[Ross]

I agree and would add that light and day length affects more than just the vegetative growth. Most plants (and most orchids) need to harden the vegetation (ie mature the growths) prior to flowering. While I have been successful in keeping a few orchids repeatedly blooming over more than a year, the growths get steadily smaller and spikes shorter. I personally don't care if I kill the plant because it's demise just gives me a space to fill with new orchids. But most folks want to keep their plants going over time and what you suggest will ultimately lead to weakened plants as "King" suggests. I try to shorten the day length as natural day length shortens - just not as short. This time of year I shorten day length by 1/2 hour every month and will keep this up until spring when I will start lengthening the "day" by increasing "lights on" by 1/2 hour each month. June is my target for 14 hour days. December is my target for 10 hour days.