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A question of light and orchids

This is a discussion on A question of light and orchids within the New Growers: Ask the Senior Members forums, part of the New Growers category; Hello My Dear Experts, My question concerns lighting. I use an artificial light source. My ...

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  1. #1
    Velamen is offline Member
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    Default A question of light and orchids

    Hello My Dear Experts,

    My question concerns lighting. I use an artificial light source. My residence has very poor natural lighting, so forget the window. I do, however, allow ambient natural light through my window where I keep my orchids to supplement my artificial lighting.

    I purchased a light stand, four feet in length, consisting of a frame with a suspended hood of the same length, which contains a T5 florescent lamp of 5000 lumens.

    Having realized after the fact that the most sun-loving orchids take up to 3000 to 4000 lumens (unless I stand corrected), I may have committed overkill with amount of lumens. However, having purchased my orchids only a week ago, I have placed them away from directly below the light on my coffee table, over which the light is suspended near the wall. Since these plants are new I have a chance to save them if anyone hollers "Danger!"

    So far, there's no yellowing of leaves though I'm on a sharp look out for them every day. I have a Cattleya chunyeah, Dendrobium kingianum, and a Calanthe vestita. I'm aware that all of these need shade to one degree or another. None are blooming now, just leaves, stems, and pseudobulbs, and the calanthe is not ready for action yet and looks like a lovely cactus plant without needles (remember, I'm new!).

    As I mentioned, none of them are directly below the light but off by a few inches to the side. The light source is also suspended at the maximum height allowed by the height of the light frame, so the light source is at about 1 to 1.5 feet above the plants. I do note, however, a rapid evaporation of water from the plant saucers beneath the pots (I elevate the cattleya and dendrobium over water).

    Also, I use a timer to give the plants ten hours of light.

    To help answer my concern if I'm using too much light, I recap the configuration:

    5000 lumen florescent bulb
    Source 12 to 18 inches from plants (depending on their height)
    10 hours of light daily
    All plants are 3 to 4 inches away from being directly underneath light source (in the bottom corner of a triangle of light formed by the light tray's shape)
    So far, no yellowing of leaves (but may be too early)
    Plants acquired one week ago.

    Thanks for reading this far. I wanted to be as thorough and precise as possible. I appreciate your patience.
    I am a newbie to orchids.

    Happy Holidays to One and All!


  2. #2
    Dorsetman's Avatar
    Dorsetman is offline Senior Member
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    Geoff Hands
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    I'm having difficulty converting lumens into the units I am more familar with - foot candles or lux ( metric system) .
    But first Calanthe - that is a terrestrial, grows on the ground in rain forest, so gets low light - 1/10th the light of a cattleya at a guess, maybe even less - I once found Calanthe triplicata growing in 33 Lux, ( about 3 ft. candles) when orchids in the canopy of the forest got light measured in K lux ( thousands of lux ).. You are making life difficult for yourself if you try to grow too wide a range in your conditions. Most cattelyas do really need it bright - I try to achieve 20000 lux ( 20K lux) on mine - which I do with 400 watt sun lamps plus full daylight . And if you go too near the lamps you may get some kind of burn.

    Leaf colour - yellow just means a dieing leaf as a rule - normal on even evergreens, when the leaf gets to the end of its life, usually because the roots directly beneath that leaf have got to the end of theirs, but 4 years life is about max. Too much light tend to lead to red colour , not yellow - think of it as sunburn.

    You have started on a long learning curve, but one worth the effort, believe me ; I have been growing for 51 years now, and I'm beginning to realise a few of the things I have still to learn...

  3. #3
    Velamen is offline Member
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    I have now placed my Cattleya directly under the 5000 lumen light (lumens are the same as foot candles, BTW) and the Calanthe on the other side of the table, away from direct light. Ditto with my Phal but not as far away. My Dendrobium is nearer to the light source. I will test this arrangement for now. If it's a matter of less light for the Calanthe my room is dark enough, even with the ambient, to move it elsewhere.

    Thanks for your help again.

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