24 hour photo period?

[Brotherly Monkey]

I was wondering if anyone ever tried treating their orchids to a continuous light cycle, and if so, what type of results did you see?

[jkofferdahl]

You'll likely see the plants perish. Plants, like people, need a rest period.

[marydaniellesantos]

I agree with jkofferdah. LOL. You should at most mimic the suns patterns.

[Brotherly Monkey]

Originally Posted by marydaniellesantos

I agree with jkofferdah. LOL. You should at most mimic the suns patterns.

Meh, I don't buy into the "mimic nature" argument. I mean, in nature, plants don't grow in my basement under artificial lights, right?

[Undergrounder]

Originally Posted by Brotherly Monkey

Meh, I don't buy into the "mimic nature" argument. I mean, in nature, plants don't grow in my basement under artificial lights, right?

Completely agree. There's no a priori reason why you can't give orchids continuous light. Two important points though..

1. I believe the only major factor to consider is the orchid's respiration cycle. A 24/7 light cycle shouldn't be a problem for C3 orchids, (mostly the thin-leaved types like Cymbidiums, Oncidiums, most Paphs). They have stomata that open during the day, and are able to photosynthesise (and grow) without requiring a dark period.

But the CAM orchids (like Phalaenopsis, Cattleyas, Dendrobiums, Bulbophyllum...) require a dark period for part of their cycle. Darkness (or absence of light) stimulates the orchid to open its stomata and gather CO2 from the atmosphere. This is stored in the form of Malic acid, which builds up in the cells of the plant.

During the day, the malic acid is decarboxylated back into CO2 for use in photosynthesis, where it is combined with oxygen and water to create sugars used in growth. Without the dark period, the plant would not be able to gather the essential CO2 used to grow.

So this is the problem for CAM orchids, But even for the C3 types...

2. Just adding more light (either through intensity or length of day) won't help unless you also increase the other major limiting factors on growth (light, water, food and CO2).

WATER is the most pressing limiting factor for growing epiphytes (and generally not light). So if you increase the light period (or intensity), you won't get better growth unless you give it a lot more water. But that's OK, let's assume you use a semi-hydroponic system and can address that need. And let's say you can feed them regularly with fertilisers, so that takes care of that.

CO2 is the next most pressing limiting factor in epiphyte growth, and this is the real problem. If you increase light AND water AND food, you also need to give it more CO2. You can do this with a CO2 tank and bump the levels up to a max of about 1500ppm (air is only 300ppm CO2), at which point the plant hits another limiting factor: The sizes of the holes in the leaves through which the CO2 flows (the stomata). More than 1500ppm is ineffective and detrimental to growth in orchids, and only so much can flow into the plant anyway.

And this is a roadblock you can't overcome. Limits on CO2 uptake will always limit growth, where extra light will just be ineffective and possibly stressful on the plant.

So my point is 1. Most orchids require dark periods for respiration. 2. Even in the orchids that don't require a dark period, there is no benefit to having the lights on 24/7 anyway... you could probably get the same growth with brighter intensity lights and an ordinary photoperiod.

[Brotherly Monkey]

Originally Posted by Undergrounder

But the CAM orchids (like Phalaenopsis, Cattleyas, Dendrobiums, Bulbophyllum...) require a dark period for part of their cycle. Darkness (or absence of light) stimulates the orchid to open its stomata and gather CO2 from the atmosphere. This is stored in the form of Malic acid, which builds up in the cells of the plant.

certainly little you can do about the above

Originally Posted by Undergrounder

CO2 is the next most pressing limiting factor in epiphyte growth, and this is the real problem. If you increase light AND water AND food, you also need to give it more CO2. You can do this with a CO2 tank and bump the levels up to a max of about 1500ppm (air is only 300ppm CO2), at which point the plant hits another limiting factor: The sizes of the holes in the leaves through which the CO2 flows (the stomata). More than 1500ppm is ineffective and detrimental to growth in orchids, and only so much can flow into the plant anyway.

couldn't this be dealt with through adequate ventilation?

[Undergrounder]

Originally Posted by Brotherly Monkey

couldn't this be dealt with through adequate ventilation?

By ventilation you mean refreshing the air with fans/windows, etc?

300ppm CO2 is what is naturally in the air, and having good ventilation would not increase the total amount available, only ensure that the 300ppm air is refreshed as it depletes. The effect is to overcome CO2 depletion, although it is comparatively a very small effect.

I know that people grow Cannabis under constant light - but whether they get significantly more growth or not I don't know. Cannabis are a much higher light plant than orchids, so more light may be beneficial for them where it is not needed in orchids.

[jkofferdahl]

Originally Posted by Brotherly Monkey

Meh, I don't buy into the "mimic nature" argument. I mean, in nature, plants don't grow in my basement under artificial lights, right?

Sounds to me then like you asked a question but don't care for any answers that differ from your preconceptions. So I say go for it - give them lights 24/7. Let us know, in about a year, how they do.

[Brotherly Monkey]

Originally Posted by jkofferdahl

Sounds to me then like you asked a question but don't care for any answers that differ from your preconceptions. So I say go for it - give them lights 24/7. Let us know, in about a year, how they do.

Not at all. I just don't accept that saying "it happens in nature" represents some logical reason for doing, or not doing, something. Especially when I am already growing in such an artificial environment


Also, if I was just going to do it no matter what, there would be little point in trying to discuss it on a message board, nor acknowledging the points raised about the physical limitations imposed by the biological processes of certain orchids

[Grandma M]

I untentionally, had my orchids under artificial light for 24 hours a day for 4 days and 3 nights in the summer. Finally my son came here to check my plants. He turned off my lights, he also remarked that he turned off my 'heater' because it was very hot in there. The 'heater' was not a heater, it was my fan.

Result: my plants suffered because of the extra light but mostly because of all the added heat. It took them a long time to recover, but they all survived.

Unfortunately my plants survived better than I did. I passed out, fell in my driveway, head first, flat on my face and I spent several day in the hospital. I survived but I did mash my face badly.

I my plants suffered because from the extra light but mostly from the heat. My lights are now, all on timers.

Marilyn