• High Moisture Absorption and Swelling: OSB is extremely susceptible to moisture. The wood strands absorb water, causing the panels to swell, particularly at the edges, which can lead to structural failure and delamination (the layers separating).
• Mold and Mildew Growth: The high-humidity environment of a grow room combined with the porous nature of OSB creates a perfect breeding ground for mold and mildew, which can destroy the panels and affect air quality.
• Off-gassing (VOCs): OSB is manufactured using adhesives that can release volatile organic compounds (VOCs), such as formaldehyde. While some modern "new-generation" OSB uses isocyanate resins (non-formaldehyde), older or standard OSB can potentially release fumes harmful to plants or humans.
• Poor Reflectivity: OSB does not have a reflective surface. It will require covering with panda film (black/white poly), reflective Mylar, or painting with flat white paint to properly utilize grow lighting.
• Structural Deterioration: In a grow setting, moisture can cause the OSB to break down quickly, sometimes in a matter of weeks, especially if not sealed properly.

• Seal the Surface: Use a heavy, high-quality primer or waterproof sealant (like pond liner or epoxy) on all sides, especially the edges, to prevent water absorption.
• Use Plastic Liner: Cover the OSB with plastic (poly) sheeting to create a waterproof barrier between the plants and the wood.
• Improve Ventilation: Ensure active air exchange to keep humidity levels in check, reducing the risk of mold.
• Use Proper Materials: Consider using plywood (especially marine-grade or treated) or white reflective insulation boards as a better alternative to OSB.

Tattooguy8 said:

Been lurking for years finally decided to ask some questions!

Been battling magnesium deficiency looking issues with slow growth and poor root health for a few years now and I just can’t figure it out.

Current situation
Peat with 30ish % perlite
Gh flora series at 2.0 ec. 2.5 ml of
2.5ml Cal mag included in ec
Ph 6.5
Room temp 84
Leaf temp right around 78
Rh 55-60
Ppfd between 150-200
24 hour light cycle in veg
Lights mars hydro fc4800 7’ off the
At 20ish percent
Using ro water at the moment

Been doing this since 96 under hid of course. A few years ago bought a new house and decided to go led. Problems ever since, especially in veg. Magnesium sick spindly, stretchy purple stems. I don’t flower sick plants but if I throw those same sick plants in my flower room in a week they will look so much better with no other changes. Not perfect but acceptable.

I’ve tried everything. Low ec, high ec, tons of runoff, no runoff, 50% drybacks to just at wilting drybacks. I’ve tried coco and peat. I even went back to cmh. Still had the issue but it was slight. Almost impossible for me to get above 250 ppfd in veg. The only thing that kind of remedies the issue is a super high ec. Like 2.5-3.0. I don’t know how everyone can run 1.4-1.6 ec at 400 ppfd at 78 degrees. My plants would literally be dead. I’m obviously having either a root zone issue or transpiration issue or both.

Another related issue, I sprout seed under a t5. Beautiful green growth with super stacked nodes. As soon as I move them to the LEDs the don’t grow new nodes they just stretch their asses off. I have to top them multiple times till they slow down and start to actually grow.

Having to add so much heat into my veg room and still have sup bar results is starting to get old. My plants would literally be dead if my room isnt above 80 degrees with a super high ec. I feel like I’ve read every leveant thread on the internet but there’s no solution. Everyone just disappears. I’m betting they go back to hid.

Sorry for the long post. Please help.

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Week4Bytch said:

Got Pics? And why 24hrs? 18 is PLENTY.

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MrSativa said:

Co2 above 2000ppm certainly is harmful.

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Tattooguy8 said:

It’s funny because my brain wants to think it’s the house or the air in the house haha. All these issues started here. They still persist even with hid just not nearly as bad. My veg room plants look pretty good with metal halide but I don’t like the way they grow. I get pretty lanky growth with mh but I think it’s from the same issue, it just shows different?

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Eastcoast302 said:

You always need cal/mag when using RO water. Are you using it in your watering?

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MrSativa said:

Do you grow in a tent or in a grow room, because this looks like poisoning to me

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Ninjadogma said:

Can you elaborate? What do you suspect it's been poisoned with?

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MrSativa said:

Co2 above 2000ppm certainly is harmful.

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MrSativa said:

I picked this of chatgpt about OSB plates and the fumes.
Back in the days with hps home made grow rooms it was a known problem.

sorry my english is not very good

Using Oriented Strand Board (OSB) for indoor growing, particularly for cannabis or high-humidity setups, presents several significant problems related to moisture, mold, and chemical off-gassing. While it is a cost-effective material, it is generally discouraged for grow rooms due to these risks.
Here are the main problems associated with OSB in grow rooms:

• High Moisture Absorption and Swelling: OSB is extremely susceptible to moisture. The wood strands absorb water, causing the panels to swell, particularly at the edges, which can lead to structural failure and delamination (the layers separating).
• Mold and Mildew Growth: The high-humidity environment of a grow room combined with the porous nature of OSB creates a perfect breeding ground for mold and mildew, which can destroy the panels and affect air quality.
• Off-gassing (VOCs): OSB is manufactured using adhesives that can release volatile organic compounds (VOCs), such as formaldehyde. While some modern "new-generation" OSB uses isocyanate resins (non-formaldehyde), older or standard OSB can potentially release fumes harmful to plants or humans.
• Poor Reflectivity: OSB does not have a reflective surface. It will require covering with panda film (black/white poly), reflective Mylar, or painting with flat white paint to properly utilize grow lighting.
• Structural Deterioration: In a grow setting, moisture can cause the OSB to break down quickly, sometimes in a matter of weeks, especially if not sealed properly.

Solutions/Mitigation Techniques:
If you must use OSB, you can mitigate some of these problems:

• Seal the Surface: Use a heavy, high-quality primer or waterproof sealant (like pond liner or epoxy) on all sides, especially the edges, to prevent water absorption.
• Use Plastic Liner: Cover the OSB with plastic (poly) sheeting to create a waterproof barrier between the plants and the wood.
• Improve Ventilation: Ensure active air exchange to keep humidity levels in check, reducing the risk of mold.
• Use Proper Materials: Consider using plywood (especially marine-grade or treated) or white reflective insulation boards as a better alternative to OSB.

Verdict:
While usable for temporary or budget builds, OSB is generally not recommended for long-term or high-humidity grow spaces due to its high risk of mold and structural failure.

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Ninjadogma said:

I wouldn't even rely on cal mag from tap, it's carbonate (wrong form). The plants want it in nitrate form. In tap it's like giving them limestone and predictably, the carbonates spike the soil alkaline.

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Eastcoast302 said:

You always need cal/mag when using RO water. Are you using it in your watering?

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Eastcoast302 said:

What’s your VPD? It could be the air & humidity causing the issue. VPD is one of the most important things when keeping a healthy plant.

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Tattooguy8 said:

Back in the day when tents were first a thing they were off gassing and making plants sick. I remember this well. Maybe 2005-2008 ish?

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Ninjadogma said:

Thats crazy. Was it a UV resin that wasn't getting UV cured and then the grow lights started doing it?

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Tattooguy8 said:

Do you have experience with the ppm that usually makes it through an ro filter? Mine is 25 ppm which is pretty normal. I wonder what it is.

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• In hydro, magnesium is best absorbed by the roots in the 6.0 – 6.5 pH range (in hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but magnesium specifically tends to be best absorbed above 6.0) If your going in at 6 and runoff is 6.5 maybe the Root zone above 6.5, maybe water at 5.6 and maybe it brings rootzone down to magnesium levels even though my understandind is
• If runoff pH is…
  
  5.5-6.5 pH – in the right range, no changes needed.
  • Less than 5.5 – provide next watering at pH 6.5
  • More than 6.5 – provide next watering at pH 5.5

1. Low Magnesium in the Growing Medium:
   Cannabis absorbs magnesium from the soil or nutrient solution. If the medium lacks sufficient magnesium, plants cannot uptake enough of this vital nutrient. Your 2.5 ml per gallon seems a bit low and you said you have been as high as 10 ml p/G. Maybe 4 to 5 for a week or two and observe?
2. Imbalanced pH Levels:
   Incorrect pH levels can hinder magnesium absorption, even if it's present in the soil. Cannabis thrives in slightly acidic to neutral pH levels. This is typically around 6.0 and 7.0 for soil and 5.5 to 6.5 for hydroponics. See above where I spoke about PH.
3. Overuse of Potassium and Calcium:
   While essential, excessive potassium and calcium can compete with magnesium for uptake, leading to deficiencies.
4. Root Zone Issues:
   Poor soil drainage or compacted soil can limit root function, affecting magnesium uptake. Healthy roots are crucial for nutrient absorption.
5. Cold or Wet Conditions:
   Low temperatures or too much moisture can slow magnesium uptake, especially in cool climates.

MercDod said:

Good Day Tattooguy8,

I hope the issues your having are not so complex as the this thread is turning. I was doing some research as I am sure you have and ran across a few things for your quick read through to see if anything rings a bell. I copy and pasted some things and added my comments.

magnesium deficiency

• In hydro, magnesium is best absorbed by the roots in the 6.0 – 6.5 pH range (in hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but magnesium specifically tends to be best absorbed above 6.0) If your going in at 6 and runoff is 6.5 maybe the Root zone above 6.5, maybe water at 5.6 and maybe it brings rootzone down to magnesium levels even though my understandind is
• If runoff pH is…
  
  5.5-6.5 pH – in the right range, no changes needed.
  • Less than 5.5 – provide next watering at pH 6.5
  • More than 6.5 – provide next watering at pH 5.5

I personally never used a dryback when using the GH flora during veg or flower, always plenty runoff to get rid of the salts and I watered every day.

Causes of Magnesium Deficiency in Cannabis

1. Low Magnesium in the Growing Medium:
   Cannabis absorbs magnesium from the soil or nutrient solution. If the medium lacks sufficient magnesium, plants cannot uptake enough of this vital nutrient. Your 2.5 ml per gallon seems a bit low and you said you have been as high as 10 ml p/G. Maybe 4 to 5 for a week or two and observe?
2. Imbalanced pH Levels:
   Incorrect pH levels can hinder magnesium absorption, even if it's present in the soil. Cannabis thrives in slightly acidic to neutral pH levels. This is typically around 6.0 and 7.0 for soil and 5.5 to 6.5 for hydroponics. See above where I spoke about PH.
3. Overuse of Potassium and Calcium:
   While essential, excessive potassium and calcium can compete with magnesium for uptake, leading to deficiencies.
4. Root Zone Issues:
   Poor soil drainage or compacted soil can limit root function, affecting magnesium uptake. Healthy roots are crucial for nutrient absorption.
5. Cold or Wet Conditions:
   Low temperatures or too much moisture can slow magnesium uptake, especially in cool climates.

6. A magnesium deficiency sometimes happens after supplementing plants with something that contains calcium but not magnesium, such as agricultural lime. Could it be something with the lime you added?

Im still searching my friend, did not forget about you.
Good Luck.

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