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Controversy on Paph light levels?

This is a discussion on Controversy on Paph light levels? within the General Orchid Culture forums, part of the Orchid Culture category; Hi everyone! Well, I've decided, probably for the better, that despite everything I've already read, ...

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  1. #1
    mauraec's Avatar
    mauraec is offline Senior Member
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    Default Controversy on Paph light levels?





    Hi everyone! Well, I've decided, probably for the better, that despite everything I've already read, experienced, heard, seen about slippers (especially paphs since I only kept one phrag when I cleaned house), I STILL DON'T KNOW WHAT I'M DOING!!!!



    Just look at all the little icon thingies that apply here! I couldn't pick just one to embody all the feelings I have about this right now....


    Anyway, as for the light issue:

    I've always read that the darker mottled-leaf need relatively low light - say 1500 - 2000 footcandles, the plain green and strap-leaved ones perhaps a bit more - say, 2,000-2500 max.
    As an aside, those of us who grow on windowsills REALLY need at least a basic lightmeter - you would NOT believe how fast the light level decreases as you move away from the brightest part of the window- when I bought one, many of my paphs were in nearly unreadable light - like 500. Wake-up call!!!

    In my case, my windows also sport double paned glass and a screen on one of the sliding doors - which cuts down at least 50% of the light coming through. Add to that that it's summer and my balcony roof shades the entire window (much higher light as fall approaches), and my highest light reading is in a very small area in front of the window (can fit maybe 4-5 plants on that top shelf) maxing out at about 3500 - 4000.

    So.... my paphs are doing okay, with the exception of the rehabbing lowii, but they're not exactly thriving. Most have new growths, but average one growth per spent growth, and these new growths are not growing too quickly.

    I know that a lot of this is shock from repotting them back into a bark mix, after having them in S/H for about 7 months (Don't panic - it wasn't that they weren't doing well, but the aesthetics of those white plastic columnar pots just got to me - if I had a greenhouse..... I'm also convinced that S/H works best with the flush and drain technique - not a small task to do by hand!). But I don't particularly like the medium they're in - seems to dry out every day, so they're about to be repotted again - a later post sometime....


    Anyway, about the light, I've read a number of "guides". Most say mottled leaf paphs need low light, like phals, green-leaved one only a little higher. Then, I've read that in the wild, paphs are used to getting fairly bright, almost catt-like light, and most paphs being grown at phal levels are not getting enough light.

    I know the test of seeing what the leaves look like. I've moved my mottled-leaf paphs into 2500 footcandle light and my green-leaved ones into 3000-4000. So far, okay, but I'd like some input from the true experts here before I leave them there too long.

    I realize that there are a number of things that all intertwine in keeping paphs thriving. I'm about to repot, because the medium they're in is drying out too quickly. I'm stepping up the humidity around them as well.

    But I'm still not sure about the light levels, though, and I'd love some input.

    Thanks!





  2. #2
    sand_tiger86's Avatar
    sand_tiger86 is offline Senior Member
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    This doesn't only apply to Paphs, but nearly all orchids for me. I honestly give up on light-levels and trying to make everything perfect. It makes no sense to me that plants which are supposedly shaded fairly heavily by trees in the rainforest require more light to flower than any other plant I've ever seen in my life. That sounds sarcastic almost, but I'm being quite literal. Ordinary flowers that need "full sun" to bloom do fine in my home, but orchids...God forbid. It's like orchid light standards are a category all on their own, while the rest of the plant world follows normal rules. It gets so aggravating. I just shove them on my windowsill lately and if they like it, fine, if not, I'm not gonna cry.

    Maybe "full sun" for a normal bulb or other flower equates to "slightly under favorable Phal light" in Orchid World.

  3. #3
    Halloamey's Avatar
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    I would not comment about light, as my experience with window sill growing is limited, but I also think that light is really not the issue for you Maura. The single most important factor that will contribute and affect the growth of your plants is how often you disturb them at roots. Orchids simply do not like it, and it is not a choice but it is unaffordable for the plant from the point of view of energy equations. Orchids are not evolved to adjust to new conditions rapidly. An orchid in wild will grow at the same spot and die at the same spot, without being disturbed. Roots provide water and nutrients which correspond to nearly 90% of wet weight of a plant. So if you damage the roots the plant is going to suffer. Orchids invest a lot of energy in their roots. In case of monopodials they double as their energy storage tissues as well. How ever careful you are while repotting you are going to damage them. and also consider the variation between the media you try. For eg. when you put your plants in SH, they had to completely change their root format to adjust to these new growth parameters, At orchid speed, it must have taken them atleast 4-6 months to adapt and produce new roots suitable for SH, and then suddenly you again change the media. The new roots now are not suitable to take in enough moisture from this drier media. Instead of changing the media, you have to adapt your other culture parameters to match your plants. Otherwise more light/low light etc will not matter because even if you make all other conditions right and the plant is already sulking you will make a wrong conclusion about those conditions.

  4. #4
    Magnus A's Avatar
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    Kelly, it is very dangerous to compare light levels in nature with those behind a glas window!
    Almost all high energy UV-light has been filtered by the glass and this can have a huge impact on light demands for flowering.

    There are also alot of other factor in flowering that you forget. Your total growing conditions differ enormous from the commersial growers greenhouse and even more from the plants natural habitat.

    I though agree with Maura that a inexpensive light meeter that give you a roughly value is a very good investment, as the human eye is extremly good to adopt to different light levels and we are unable to correlate light levels.

    Edit: and I agree with Amey Bhide above that manage to post just before me .

  5. #5
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    Maura, 3K - 4K footcandle light on even a strap leaf type slipper orchid is too much and a risk of burning the plant (in my opinion.). Growing in a green house I have found that some of my phrag orchids like light up to 3K foot candles, but paph orchids (both the darker leaves and the strap leaf) grow better in light ranges of 1000 – 1500 foot candles. JMHO

    cheers,
    BD

  6. #6
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    Quote Originally Posted by sand_tiger86 View Post
    It makes no sense to me that plants which are supposedly shaded fairly heavily by trees in the rainforest require more light to flower than any other plant I've ever seen in my life. ... Ordinary flowers that need "full sun" to bloom do fine in my home, but orchids...
    Can't help with the paphs as I just kill them, but addressing Kelly's point:

    "Shaded fairly heavily by trees " is a descriptor that must be taken with a large grain of salt ... in some cases an entire salt block. People tend to erroneously apply this to ALL orchids. It is simply not the case. Yes there are orchids (such as the jewel orchids, and some of the paphs) that do indeed grow in fairly heavy shade it the wild. However, as has been pointed out, light levels in "fairly heavy shade" outdoors is generally VERY different than what our eyes would determine to be 'similar' conditions indoors. (Judging light levels for plants by 'eye' is a notoriously poor method. Even though humans do not have anywhere close to the best eyesight of the creatures living on this planet, our eyes are still incredibly sensitive to light. The light energy required for photosynthesis far exceeds the levels we need in order to see well.)

    Do recall as well the reason so many orchids are epiphytes -- as a means of escaping the dim understory of a rainforest so they can instead grow in areas receiving MUCH higher light levels. I have seen photos of catts in the wild and they were by no means growing in "fairly heavy shade". Far from it. Rather they often were growing where they were receiving direct, unfiltered sun for at least part of the day.

    While I do not know which other plants you are growing indoors, Kelly, the simple fact is that many if not most of the plants commonly sold as houseplants are NOT full sun plants in the wild. Many of these 'full sun' plants, if placed outside in full, unfiltered sun would fry. Just as an example, african violets typically do well on a sunny east facing windowsill in my part of the world. But this light is filtered by the window glass and further by any screening if such is present. Placing one outside in what would appear to be similar conditions (just minus the glass and screening) would generally result in one very unhappy and, in all likelihood, dead plant. Why? Because those indoor conditions are not the same as the outdoor conditions -- despite what our eyes would try to say. African violets, in fact, ARE understory plants. Yet if you were to attempt to grow one under "heavily shaded" conditions indoors, you would not see any blooms, nor much if any healthy vegetative growth, and again a steady decline to death would almost be assured.

  7. #7
    mauraec's Avatar
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    Thanks, everyone, for your feedback! Amey - thank you for the reminder about switching media and damage to the roots - I have been painfully aware of those consequences in the past. I really switched them out of S/H because I couldn't keep them damp enough without draining and flushing each one at least once a day, and once a week fertilize weakly - for 100+ orchids that was about 6 hours taking them back and forth to the kitchen sink, waiting for them to drain - for 25 or so, it took about 2 1/2 hours a day - just for watering - and that doesn't include dealing with thrips, mealybugs, fussing around with light exposures, and researching each new orchid I acquired. They did really well, but, since I do have another life, I needed a medium that will allow me to water (again, individually) at the most 3 times a week. The S/H system I had had pots with 2 holes about 1" about the bottom, and that reservoir dried up every day, plus the clay pebbles above dried completely even before that.

    Believe me, with the air conditioning on inside, root rot has NEVER been the problem; every time I check my plants, they're as dry as dust. I found. Since I obviously don't want to disturb them again, I'm trying to figure out what "dressing" I might be able to spread over the pot surface to help retain moisture without suffocating them. Any thoughts?

    There's no question they're sulking from being repotted, but they would have sulked a lot more if they had dried out completely for a week at a time - remember, I have almost all slippers - just a few catts and they get the benign neglect treatment outside. I would say that they are not taking a turn for the worse, just not pushing forward as much as I had hoped. And, unlike other orchids, paphs actually LIKE to be repotted every 6 months to a year. I was counting on that somewhat, even with the medium changing.

    One thing I started to slip up on was keeping my humidifiers cranking - I'm rectifying that and know they'll be happier for it.

    This light question has really been the only thing bothering me (well, that, and the constant watering, but I'm working on that). My indoor light levels are significantly higher in the fall and winter (the sun being lower in the sky, and thus shining more directly for longer periods through my windows), so summer has brought with it this new set of problems. The orchids that can go outside - my cym, 2 encyclias, and 5 catts (all of which have undergone the repotting ordeal), are thriving at about 4,000-5,000 footcandles. But I think the slippers inside are suffering a bit. I've moved them around as best I can so that they're getting an average of 1800 or so, except for my kovachii hybrid, which is in the place of honor at about 3000.

    I do think that the species slippers prefer more light than the greenhouse-created and 30-generation hybrids. My confusion was simply that, as I've read more and more about lighting, I've come across more and more differences of opinion and the only way out of this confusion, as I see it, is to check with y'all about it.

    By the way, my Paph. lowii has perked up in the last week since being moved to about 2200 footcandles, so I'll keep an eye on that. Tomorrow I leave for Maine for a week, so Phillip is going to have to man the stations by himself. I wanted at the very least, to leave him with instructions as to where the various orchids should stay located. He's going to have plenty on his hands between my orchids, his orchids, the bonsais, and the fish. Oh boy....

  8. #8
    pavel's Avatar
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    Forgot to address the only areas of your query, Maura, with which I might be able to help.

    As far as a "top dressing" goes, a layer of sphag might do the trick.

    More moisture retentive media: Next time you repot, you may wish to try coconut husk chunks instead of bark with a few plants. The chunks are more water retentive by far and actually break down less quickly than bark. The chunks do come in different sizes. If you wish to give it a go but have trouble locating sources, pm me. NOTE: As with any new medium, there will be a bit of a learning curve for you as you determine how to best adapt your watering with a different mix.

  9. #9
    mauraec's Avatar
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    Thanks, Pavel. I really do appreciate your advice (even if you do say you're a slipper-killer) I'll definitely be putting it to use.

  10. #10
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    I'm sorry I know next to nothing about growing indoors, under lights or on the window sill. On the subject of paphs, I find that I have to use two layers of 50% shade cloth while the other orchids need only 1 layer; how that translates to foot candles I don't know.

    But as to mottled leaved paphs I have seen niveums on very exposed locations in the wild, in Langkawi Island they grow almost to the water's edge, but on the limestone hills near where I live they grow on the cliff sides exposed to the morning sun but heavily shaded from 11 am onwards. The other mottled leaved paphs I'm familiar with is Paph barbatum and they grow beside very heavily shaded streams and runoffs in moist, living sphagnum. So I think we can't generalise and say that all mottled leaved paphs should or should not be exposed to more light or less light. Having said that I reckon the Brachypetalum's can tolerate more light than the Sigmatopetalum's.

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