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Thread: Diagnosis request: phrag orchids with green veins, yellowish leaves

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  1. #1
    Join Date
    Feb 2020
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    Default Diagnosis request: phrag orchids with green veins, yellowish leaves

    I could use some diagnosis here. I have two phrags that grow vigorously but the leaves are more yellow/washed out than I am used to seeing and the veins on the leaves are visible and green. Is this a nutrient issue? Too much light? The yellowing is not blotchy.

    Culture: Grown under platinum LED lights. Bright Catt-level light.
    semi-hydro with Leca
    Watered weekly with RO water and K-lite (75ppm)

    They are growing very well but look to have a deficiency, too much light, or something. Would appreciate any input.
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  2. #2
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    Ray Barkalow
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    Oct 2012
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    Default

    Even though K-Lite contains 3% Mg, I suggest you experiment by adding a teaspoon of Epsom Salts per gallon to each watering or feeding for the next few weeks. It may be that the plants just haven't accumulated enough to sustain a decent growth spurt.

  3. #3
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    Feb 2020
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    Default

    Hi Ray,
    Thanks for the input! I have a gallon of CroMg lying around. Would that work? If so what dosing level would you suggest?
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  4. #4
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    Ray Barkalow
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    I don't know the product, so cannot make a dosing recommendation, but in general I wouldn't add more calcium (I assume "CroMg" was meant to be "Cal-Mag", and not a jar of ground-up, early hominids).

  5. #5
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    Bruce Brown
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    Quote Originally Posted by raybark View Post
    .....and not a jar of ground-up, early hominids).


    cheers,
    BD

  6. #6
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    Lol... the hard part is getting them to sit still while you grind them up

    And yes - meant CalMg... working from memory.😊
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  7. #7
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    Geoff Hands
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    According to Guidso Braem's new book on phrags , they don't like fertiliser. Not suggesting none, but certainly only low levels.
    If you use Elec. Conductivity ( measured in uS - the little u should actually be a Greek mu) then 200 is max. Can't remember how that equates to ppm/TDS since there are so many different standards for TDS meters, some multiply EC by 1.5, some 1.6, and I even found one using 2.0. I'm not trying to blind with science, but many folk do not realise that there is no meter ever invented which can actually measure TDS ; but measuring the EC is easy - it is a simple electrical measurement of resistance, then using the reciprocal for conductivity - although the levels are very low !
    So take the EC , multiply by a constant, and you have TDS. The constant by the way assumes that the stuff dissolved in the water, the fertiliser, is a single compound, say Calcium nitrate or whatever , and the reason for different values, is that they are for measuring different chemicals,

  8. #8
    Real Name
    Ray Barkalow
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    Geoff is right, there is no "constant". Here's a couple of articles I wrote on the subject: Don't trust your TDS Meter and TDS & EC.

    True TDS is simple: 200 ppm is 200 mg of dry fertilizer dissolved in a liter of water. For K-Lite fertilizer and MSU RO (and Akerne's Rain Mix), that comes in at around 35 ppm N. However, I can tell you from experience that my plants - including several phrags - are doing fine at a weekly shot of 100 ppm N solution at about a TDS of 770 ppm - my two meters tell me it's 395 and 475 ppm, to Geoff's point.

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