Tom,

Your experiments on metabolism are very interesting...
I'll add my thoughts...

I grow intermediate and warm growing plants. In the late winter/fall, my growing temps range from 58-75 and in the spring/summer they range 64-84. My warm growers grow more slowly (and most of them start to spike) during the winter/fall. The intermediate growing plants grow like gangbusters in the fall/winter, but slow down when the warm temps of spring/summer come. The intermediate growing plants tend to spike when they get a slight cooling in the early Fall after slowly maturing growths over the summer.

As far as day length, some unifoliate species catts will not bloom. According to Ortho's All About Orchids, C. labiata, mossiae, percivaliana, and trianaei are all sensitive to day length cycles, as is Bulbophyllum falcatum, D. phalaenopsis, Onc. splendidium and even Phal. amabilis. (This is on page 49 of the book. I wanted to share this information because I re-read the book this week-end as a refresher and finally found this information. I know a lot of people ask about it on the forum.) However, for a hybrid this should not make a bit of difference. Most growers recommend 16 hours of daylight year-round under lights. I cycle my lights to follow natural daylength because my growing area is an East bay window.

My understanding of this is that it's not just about flowering a few species that respond to day length. What I have read is that a period of darkness is required for completing metabolic processes begun during the day. So withholding darkness isn't a matter of not producing flowers, it's a matter of actively hurting the plant.

I've never found plant biology interesting enough to learn the details, but this makes sense to me.

Not to be argumentative, but while what you did can be called an experiment, it's not of a type that allows conclusions "beyond a reasonable doubt."

I hope we have someone versed in biology here who can chime in, because there is a risk attached to doing it your way without more information.

Looks like you had some interesting experiments going on. My own two cents here:

Regarding the daylength, I would NOT recommend to give them all the light you can. All the light they can take during the day, absolutely! But all plants still need a dark period for optimum health. To deprive them of a dark period would result in a gradual decline in plant health over time. In a slightly related topic, native trees that are deprived of their dormancy come back spindly or just plain die. Plants can't keep going and going, they need a break eventually.

Where the temperatures are concerned, it would make sense that you would want to keep the plant temps above 70 during the winter. All the plants you mentioned are tropical plants, and during the winter in say Brasilia, Brazil, the typical winter high is about 70. ITs what the plants are used to. Growing in lower than average conditions will reduce vigor and in one experiment i performed on beans can result in a mild dwarfism.

Thanks for posting your findings, very cool!

Hi All,

Thank you for your comments. By adding your experiences and knowledge to the post, we all gain from your insight. The more discussion the better.

I'll try to add a few more pieces to the puzzle.

History: Garner and Allard of the USDA (accidentally) discovered photoperiodism in plants during the 1920s. They were studying how to grow better tobacco. Unfortunately, their plants failed to bloom in the field. In fall, as frost approached, they quickly dug up the valuable crop and moved it into a greenhouse. As the daylength decreased, the tobacco bloomed. Photoperiodism!

Moral of the story: Even a poorly designed experiment can yield important results.

Garner and Allard went on to describe three groups of plants; Short Day Plants, Long Day Plants, and Day Neutral Plants. Most of the following experiments focussed on food crops (soy beans, onions, strawberries, potatoes, radishes, yams, etc). Only a handful of garden flowers and houseplants were tested (dahlias, chrysantheums, Easter lilies, poinsettias, etc). Very few orchids have been tested.

Clint posted an excellent list of short day orchids. I wonder if there are more that others know about. Please add to Clint's list.

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Mehitabel, I always have reasonable doubt about my experiments :-)

You raised some great issues. I'll try to comment.

There are two parts to the photosynthetic reaction in plants: light reaction and dark reaction. Blackman, an English physiologist, discovered that part of the reaction required chemicals, enzymes, and CO2, but it did not require light. He coined this as the dark reaction. Unfortunate wording tends to make you think that this reaction only occurs in darkness, which is not true. This part of the photosynthetic reaction does not require light, but neither does it require darkness. Great concept, poor choice of naming.

Many commercial greenhouses grow stock under continuous 24 hour lighting conditions. Nearly all commerially grown annual flowers are grown this way. Lesser so for other crops. Again, few people have ever researched this topic with orchids.

Mehitabel, I do have a whole bunch of botany degrees hanging on my walls to keep my wallpaper from yellowing. It's merely my poor writing skills that keep me from expressing my observations properly. My fault. I tend to get all excited about growing plants, but then fail to get all the words right.

What I meant to say is that some plants do require a period of darkness to flower. Some plants grow better (metabolism) with a period of darkness. But some plants grow just fine under continuous 24 hours of light and these plants are not hurt by lack of darkness. I wonder which way orchids grow best, and flower best. Can orchids be grown under continuous light (longterm) without hurting the plants. Great points Mehitabel.

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Terpguy, thanks for your comments. I agree, we should not recommend that everyone start growing under my experimental conditions. However, if someone would like to sacrifice a few orchids under continuous 24 hour light conditions for a few months, and then report back to us - that would be great.

If you get an orchid to bloom, you have just found another species that is not a short day plant. Perhaps someday there will be a long list of tested species and we can all benefit from the shared knowledge. You don't need a fancy lab to run this experiment. You just need to keep the lights on.

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To the other readers, jump in and share your knowledge with us. If you have observations about growing under warmer winter minimums and/or growing under continuous lighting conditions, we would love to hear your experiences.

Tom

Sorry, Tom. Did not mean to diminish your credentials.

I think I will continue to obsess about providing the darkness period for a while :)

I wonder if they grow any orchids in Alaska? They have six whole months of daylight without any night at all. I know they grow spectacular spcimens of veggies and flowers.

Increased temperatures will result in increased growth and quicker blooming IF there is sufficient light. If you artificially inflate the temperature without sufficient light, your plants will get elongated segments, making them "leggy" to look at and softer in structure, and they will not have built up sufficient energy reserves to bloom properly, if at all.

In the last part of the AOS article on growing Phals, growers shade the plants with heavy shade cloth (almost dark) to discourage spiking. High temps and shade encourage green growth. Higher light and cool temps encourage spiking.

I lost my magazine and can't remember the specifics, but there was a photo of a commercial greenhouse, totally shaded, almost dark, with immature Phals growing. They had to loosen some of the shade cloth to be able to get enough light to take the photos.

Was amazed at how dark the greenhouse was.

Jane

All of this is painfully exciting for me to read (I wish I had the space and the plants to do that). Spending quite a bit of time another magical plant last year.(it starts with C, ends with Sativa, and has annibus in the middle) Photoperiod was the only factor that regulated flowering. I assumed all plants were like that (even though assuming all of anything is stupid). What tells orchids to bloom? And since you have degrees in this sort of thing... I recall, last semester, learning about volitiles, the only one I remember being jasmonic acid (used to warn other plants of insect attack), so are there any orchids that release volitiles to communicate, aside from the fragrances of flowers?

Good question Bob. Well, orchids love to attract ants. They send out loads of sticky honey dew, which the ants devour. Hornets love it also and literally get drunk on it.

As far as letting each other know of an impending insect attack, I certainly doubt it. They can all sit around getting covered in scale or mites without running away.

What tells orchids to bloom? Each plant has it's preferred growing conditions, provide that and you get flowers...sometimes. Some, on the other hand, flower when they think they are doomed. Give them too much of a good thing and you get green growth, give them little - flowers.

The joy of gardening,
Jane

The reason I ask (yeah its crazy) is that a friend of mine is writing a book and my charater is an elementary school teacher and orchid enthusiast by day and a sinister vengeful orchid enthusiast by night. I need to exact revenge on the main character for killing my father. I was thinking I could breed an orchid with the plant that attracts parasitic wasps when a certiain worm with volicitin in its saliva starts to eat it (in the story, not real life). I could send the main character my new breed of orchid and when he cuts the bloom per the instructions hundreds of parasitic wasps try to lay eggs inside of him. The honey dew is promising. (I couldn't resist yesterday, and I tasted some of it; it really is sweet!)
As for the flowering, so it just decides to do it when it decides it has put on enough new growth, and given that the conditions are met it will just happen, it isnt regulated by the seasons at all? For instance, if I grow orhids indoors with the same intensity of light for the same amount of time every day the plant will just spontaneously flower. right?

No. They all have different requirements, light, temps, watering, etc. Pick a type and read up on it. Then work it into your story.
Scary thought...

Jane