cbdhemp808
Well-Known Member
So, what do you think? too much humidity in this case?
Canoeing leaves
- Thread starter Cheschire
- Start date
led causes a completely different type of damage in the absence of heat, it looks more like a genetic disorder. led photons are capable of damaging a leafs cell walls, if placed too close or turned up too high. it is unique to led and looks nothing like regular heat damage.
even a weak led can cause it if placed too close. regular heat damage can also occur but is less common.
600w is 600w. they both will produce the same heat if consuming the same level of energy. it's part of the law of thermodynamics.
where led differs is the ability to produce more light with less input than hid sources. that is what the black dog folk were measuring.
i'd also be suspicious of how that got measured. i can change a reading on a laser thermometer by 10c just by moving a couple inches closer or further out. you have to literally mount the things on a tripod and measure the exact same spot across several locations at the same distance, then take an avg.
i've used a professional laser therm in a work setting. the thing cost a few thousand, most of your garden variety can tire models just won't have the same level of accuracy.
indoor air movement, extraction, and rh will all effect that number as well. you should expect the surface leaf temp to be a bit lower than most ambient temps. the plant creates a 'micro-climate at the leaf surface to help it transpire and accomplish photosynthesis.
it's a number often cited for growers contemplating c02 or married to a vpd chart. it's mostly a ballpark and does not reflect reality. normally you want similar conditions for growing regardless of the light source.
the 10 degree decree is a hold over from a long line of longstanding hid users trying to adapt to led. it's not really adhered to anymore.
it's possible. it just may not be cost effective to put what is needed in to control the environment that closely. vpd is also a range, it's not one exact set of conditions, things can vary and still be pretty well within decent growing conditions.
vpd is a tool and not a hard pressed rule. most folk wind up growing inside of it without ever knowing. we did grow weed before those charts existed guys
those controllers are great. even a fan speed control is a good idea. i'm still using a speed control in the veg room and am contemplating upgrading.
the flower space has no control at all, and it moves about 6 times more air than i need lol.
i re-used the fan from another much larger space. it's an old school monster snail. we might incorporate a damper on the exhaust. that's how it was done old school.
best guess is a combination of heat / rh / light. vet's growing in a known high rh climate. i'm ruling out any root issues as @VetSmoke85 knows what he's doing. temps seem fine, leaving rh and light. he can't affect rh effectively, so he pulled the light a bit and reported an improvement.
cbdhemp808
Well-Known Member
It was a sophisticated test setup, computer controlled with all the plants at the same height. They used a FLIR i7 infrared camera to measure leaf surface temperature (~$3,000). (sorry, link to article was moderated out.)
The OP reported in the beginning of the thread that the light was at 32" and at 50% strength, so it appears there's no way it was heat-related with a 300w LED at 1/2 power, and ambient temps 70-75.
None of this seems to be enough to cause cupping/canoeing.
Perhaps over-fertilizing... I think @Bill284 was onto this.
Or, calcium/magnesium deficiency.
Delps8
Well-Known Member
That might be a reason why things are out of kilter. Photons generated by LED's are different than photons from any other source and the i7 doesn't compensate for that.
Here's the trick that we old timers used back in the day - you'll get a lot more accuracy if you multiply the displayed temperature by a factor of 1.000. The extra zeros are needed or the quantum inversion ratio that's used by the i7 will descale asymptotically. How it all works is pretty complex but can trust that I know what I'm talking about because I'm on the internet.
cbdhemp808
Well-Known Member
I added some more to my reply above. They also used a "StellarNet spectroradiometer" to determine the light spectrum at the hanging distance.
The main purpose of the test was to measure leaf surface temps.
Are you telling me that 150w of LED at 32" (2.7 ft) above the top of plant is going to cause leaf canoeing? I don't think so.
Delps8
Well-Known Member
No - my reply was a nonsensical tongue in cheek response addressing the idea that photons from LED's are "special" in a very passive aggressive way.
The idea that a $20 IR thermometer is not sufficiently accurate to grow cannabis completely ignores that huge number of variables and inaccuracies that impact the many months long process of growing cannabis. Sure, if it's off by "many" degrees that will have an impact but a couple of degrees either way is not a show stopper.
I'd suspect that at 32" hang height, the amount of heat added to a canopy by a 150 watt LED grow light would be very hard to even measure.
cbdhemp808
Well-Known Member
So I think you agree – the cause of the canoeing wasn't heat from the light.No - my reply was a nonsensical tongue in cheek response addressing the idea that photons from LED's are "special" in a very passive aggressive way.
The idea that a $20 IR thermometer is not sufficiently accurate to grow cannabis completely ignores that huge number of variables and inaccuracies that impact the many months long process of growing cannabis. Sure, if it's off by "many" degrees that will have an impact but a couple of degrees either way is not a show stopper.
I'd suspect that at 32" hang height, the amount of heat added to a canopy by a 150 watt LED grow light would be very hard to even measure.
What do you think of over-fertilizing or cal mag deficiency?
Delps8
Well-Known Member
Yes.
Nutrient burn, a Ca deficiency, or an Mg deficiency.
There are numerous deficiency charts floating around - they're your best guide.
I've had an Mg deficiency and the big indicator for that was interveinal chlorosis. That stood out like a sore thumb. When I looked at your plants the first time, that's what struck me - the lime green color between the veins of the leaves. Interestingly, it's in just one plant - is that one older? I ask that because the stems are so much longer that it looks like that plant is more mature.
A Ca deficiency just popped up on my current grow with the only symptom being tan/brown spots in the center of the leaves. Again, very easy to spot.
Re. canoeing - I think excess light can cause that. I've had a few instance of excess light. The most common reaction has been light avoidance, meaning that the plant has reacted by changing the orientation of leaves not by changing the physical shape of the leaf.
Over to Google - "what causes cannabis leaves to taco" and, lo and behold, the common answer is heat and humidity issues.
One response deals brings up having too much wind on the leaves. The logic behind that is that too much wind drives up the transpiration rate which ends with leaves drying out because the stems can't pass enough water to keep the leaf cells turgid.
I've attached a screenshot from Bugbee. Work through the chart, eliminating the items that you know are OK and that will point you in the direction of the culprit.
I've never had fertilizers cause canoeing.
Generally rh and heat.
What's the VPD?
Stay safe
Bill284
there's a report out this morning on how the laser therms won't properly measure the temp of a black person. doctors and hospitals have been advised to use standard therms when measuring patient temp.
the laser therms are sensitive to the color of what they are measuring. it's a flaw all of them have, no matter the cost.
I tried using our laser temp thermometer on the leaves yesterday. Just says 'low' as they're probably a bit below what is normal for a human. Ha ha.
i used to use them when mixing the base for fibreglass. they will measure semi-solids and heated liquids far better than anything else.
Measured mine and my youngest son's temp the last couple of days. 39-40C. We've both tested positive for COVID today. The Mrs just tested positive too. Explains why I felt so crap. Lol
oh no. i got sick a few wks ago and probably had it. my boss made me work through it, and then 2/3 of the work unit got sick and went down immediately after. 2 folk wound up in hospital. then he took 2wks off for himself over it.
Yeah that sounds like COVID. Thankfully feeling much better today compared to the last couple of days. Pain in my chest and rubs has got a little worse but the headache and fever have subsided. That headache was brutal so I'm glad it's gone for now.
i'm just glad we didn't lose anyone. we all got lay off notices as soon as it was over. i got 15+ yrs in. a whole 2wks severance as a thank you.
That's awful mate.
So the majority of its been hashed out but I believe you’re seeing a few things. You said r/o water that you just added calmag to last watering. R/o waters usually are stripped of your average tap water nutrients including calcium and magnesium. You also have a fairly high VPD going for the stage you’re in.
I think you’re seeing your plants perform light avoidance because they’re lacking the magnesium needed to photosynthesize at the rate your environment is demanding of them. The calmag was a good call.. Be careful not to overreact now that you’ve started to narrow your issue and please keep us updated!
I think you’re seeing your plants perform light avoidance because they’re lacking the magnesium needed to photosynthesize at the rate your environment is demanding of them. The calmag was a good call.. Be careful not to overreact now that you’ve started to narrow your issue and please keep us updated!
cbdhemp808
Well-Known Member
Me neither! only heat.
