Day Length
 

How many hours a day do you run the lights in winter vs summer? thanks, Mike

Bump.

I don't grow orchids under lights. But winter daylength in and near the tropics is around 10-12 hours. It may be sufficient to extend the natural day by running the lights for a few extra hours before morning and/or after evening, or both, and turning them off during the day.

I have a Phal parishii and a Schoenorchis in a small terrarium. They get 14 hours of light year round.

This is where artificial lighting is losing me.

You do you calculate the amount of time needed, based on µMol, PAR and so on?

Under LEDs, some of my plants have gotten a purple tint, meaning (if I'm not mistaken) that they're getting enough light.

Yet they get 8 hours, which is waaay less than your 14 hours.

Night length is important to some plants.

Windows in sunroom face west, one set faces south. Northeastern Kansas setting. New setting, as prior they were outside May through September and no artificial light needed. Rest of year in a basement, twelve hours of artificial light daily.

Now in sunroom I'm doing twelve hour light from 7:00 a.m. to 7:00 p.m. from October through May, because more clouds that time of year. June through September 7:00 a.m. to 2:00 p.m. That's the plan anyway.

So it's based on YOUR growing space, YOUR particular weather patterns, etc. Sharing any of that information would help others to be more specific.

You calculate how much light your plants need by published and anecdotal reports of their DLI (daily light integral)

Low light orchids need a DLI of 4-6 wheras high light orchids grow best between 12-15+ DLI. Many grow light manufacturers have published PAR values for their fixtures at given distances you can use this to estimate the PPFD at your orchids height and then use the chart in the link to figure out how much DLI that plant is getting.

If you work you can shift the start/stop times so the lights are on when you are home. When I lived in St Louis I had the lights on 6 pm to 4 am. The plant were in the basement or in an upstairs room with the drapes closed.

Yes, the DLI is important, but it’s not as simple as “x” hours of light and “y” hours of darkness. If that was the case, double the intensity for half the lighted time would be fine, and it’s not.

There are chemical processes in plants that occur in light and others that occur in dark conditions. They are also affected by temperature. A plant, like a phalaenopsis, that has evolved in a long-day, low light environment can live in a brighter, shorter-day one, but those chemical processes will not compliment each other as well for the overall well-being of the plant, so it will not perform as well.

That's a VERY good point Ray, thanks for that.

Do you have more information about those processes?