Photoperiod - what is the appropriate 'winter'?

[rbarata]

My Phals just bloom reliably, and seemingly on their timetable. I don't do anything except water and feed.

Yes, that's what I do too.
In winter my cool growers are at 12~15 ºC (54~59 F) most of the time. My warm growers are at 15 ºC (59 F) by night and 22 ºC (72 F) during the day.
In summer almost all the house is between 24~28 ºC (75~82 F) most of the time.
I guess people living in hot summer climates find it easier to have blooms since the diferential is more noticeable.

[rockyfarm]

The seasons are what they are, but they don't have to be. Witness growing southern hemisphere plants in the north where they adapt to our seasons. Plants have capabilities to perform 'better' where environmental factors allow them to, and (under lights) we largely control that environment. The reliance of plants on seasonal triggers, such as lower temperatures and shorter days is adaptive to the suite of conditions associated with those triggers in the natural environment. But it's not adaptive to my grow room, where I will not freeze them or desiccate them. I want to reduce the low-growth circumstances to the minimum needed to trigger blooming or new growth.

[Leafmite]

That is a good way to think of it. I have a guava getting ready to bloom, am harvesting herbs and strawberries, I have some limes growing...in the middle of winter.

I found the first year, when I still had the large Cattleyas, that some of my species orchids that normally put out just one set of growths started a second round under the lights. My smaller Cattleyas tend to just keep pushing out new growth and bloom under the lights. However, I am not sure if these ones have an exact season. In the windows, everything tended to rest at this time due to the lack of proper light. For the window-growing plants, I see a slow-down in growth with everything except the passiflora (of course, I want this with the Venus fly trap and pitcher).

[rbarata]

I want to reduce the low-growth circumstances to the minimum needed to trigger blooming or new growth.

Basically you want to do what fruit producers already do, such as producing strawberries in winter and oranges and grapes in summer (for ex.).
The difference is that they already know what to do.
I think you should look genus by genus, specie by specie.

[voyager]

I'm skipping over most of the discussion and am addressing the OP's original question.
I grew orchids for over 10 years with no artificial lighting at 61°North.
That translates to 19-1/2 hour summer days and 4-1/2 hour nights. Winters were the opposite with 19-1/2 hour nights and 4-1/2 hour days [at the solstices].
Except for a Catt. maxima, I avoided hight light orchids like Vandas and Catts. Although, others didn't and were successful with them.

Some were very problematical.
Bamboo Orchids [Arundina] were very difficult to bloom.
But, I could do it.

I never had problems with Dendrobium, Oncidium, Phaius, and other species plants that supposedly needed high winter light. All I had to do was follow the cultural requirements for each of them while tweaking temps, water and feeding.

[rockyfarm]

Originally Posted by voyager

I'm skipping over most of the discussion and am addressing the OP's original question.
I grew orchids for over 10 years with no artificial lighting at 61°North.
That translates to 19-1/2 hour summer days and 4-1/2 hour nights. Winters were the opposite with 19-1/2 hour nights and 4-1/2 hour days [at the solstices].
Except for a Catt. maxima, I avoided hight light orchids like Vandas and Catts. Although, others didn't and were successful with them.

Some were very problematical.
Bamboo Orchids [Arundina] were very difficult to bloom.
But, I could do it.

I never had problems with Dendrobium, Oncidium, Phaius, and other species plants that supposedly needed high winter light. All I had to do was follow the cultural requirements for each of them while tweaking temps, water and feeding.

Very interesting. My original question was how short a time could I supply 'winter' light, and temperatures for that matter. Your far-north winter had very long nights, but these were still over a period of about 3 months, I presume. With supplemental light could you have had successful blooming, dormancy, and more rapid growth?

[Subrosa]

Originally Posted by rockyfarm

The seasons are what they are, but they don't have to be. Witness growing southern hemisphere plants in the north where they adapt to our seasons. Plants have capabilities to perform 'better' where environmental factors allow them to, and (under lights) we largely control that environment. The reliance of plants on seasonal triggers, such as lower temperatures and shorter days is adaptive to the suite of conditions associated with those triggers in the natural environment. But it's not adaptive to my grow room, where I will not freeze them or desiccate them. I want to reduce the low-growth circumstances to the minimum needed to trigger blooming or new growth.

That's a one time acclimation. Once such plants are adapted to the seasons of the opposite hemisphere they completely "forget" about the seasons of their native hemisphere. And how great of an acclimation it is depends highly upon the seasonality of the specific plant. Acclimating tropical plants found near the equator to the opposite hemisphere is practically foolproof. Acclimating ones that seasonally die back to the roots is a completely different kettle of fish.

[Subrosa]

Originally Posted by rockyfarm

The seasons are what they are, but they don't have to be. Witness growing southern hemisphere plants in the north where they adapt to our seasons. Plants have capabilities to perform 'better' where environmental factors allow them to, and (under lights) we largely control that environment. The reliance of plants on seasonal triggers, such as lower temperatures and shorter days is adaptive to the suite of conditions associated with those triggers in the natural environment. But it's not adaptive to my grow room, where I will not freeze them or desiccate them. I want to reduce the low-growth circumstances to the minimum needed to trigger blooming or new growth.

Double post

[voyager]

Originally Posted by rockyfarm

Very interesting. My original question was how short a time could I supply 'winter' light, and temperatures for that matter. Your far-north winter had very long nights, but these were still over a period of about 3 months, I presume. With supplemental light could you have had successful blooming, dormancy, and more rapid growth?

Light decreases from the autumn equinox [mid Sept.] where the day is split evenly at 12hr each for day and night.
Then, from the winter solstice [mid Dec.] where the day is split @ 19.5hrs/4.5hrs day/night, light increases the opposite from the winter solstice to the spring equinox [mid March].
At the mid point between the equinoxes and the solstices the day length is changing at 5 to 7 minutes a day, decreasing in the fall and increasing in the spring.
Tropical plants usually prefer a 12hr/12hr day/night cycle.
I think they might be considered light starved for as long as 4 months or more at that lattitude.
I was able to successfully grow and bloom regularly the cool dry rest type Dendrobiums that supposedly required high winter light to be able to bloom in the spring, February and March.

Many [several?] people in that area did use artificial lighting to good effect.
It made growing Vandas and Catts much easier.
Because I grew in my living room, I refused to use artificial lighting.
I wasn't going to have large HO fixtures or other high intensity lamps hanging all over the living room or have to wear sunglasses at night to watch TV or a computer monitor.
Some things I just will not do for the orchids.

[rockyfarm]

Exactly; we grow orchids for our pleasure, not industrially. The lights I currently use are 100 watt equivalent LEDS, warm and cool white, so they are not blinding (especially since they are in reflectors), but nicely warm the grow room during daylight hours. I keep the TV and computer upstairs, where humidity is lower too.