Since you're ruling out heat right away, I did a siterip of a page I found useful, it's from 2008. It's alot of text but might have ideas in it that apply to you.
Leaf Edges turned upwards, heat stress indicated but temps are good.
-indoor or outdoor
Indoor
-soil, soilless, or hydroponic
Soil
-Soil type/brand
50/50 mix of Promix and Fox Farms Ocean Forest
-Anything you have added to the soil
Perlite, about 20% mixed in.
-Soil pH
Between 6.3 and 6.8
-Water source
Just tap water.
-Water pH
PH of water alone before adjustment is 7.3
-Age of plant
6-7 weeks old on average.
-Type of fertilizer
Age old Bloom and Hydroplex Boom Booster by botanicare.
-Rate of application
Once a week
-Lighting source and distance from plant
400 Watt HPS, 18 inches away from majority of the canopy. 10 inches away from the highest stray side shoot.
-Temperature (both day and night if you are running a dark period)
Temp at 18 inches away is 75.6F degrees.
Temp at 10 inches away is 82F degrees
Temperature at night is about 68 degrees at it's lowest.
-% Relative humidity
Currently at 38-40% RH.
-Lighting schedule
12 on / 12 off. Lights go on at 6am and go off at 6pm, which is about the same for natural lighting right now where I'm located.
-Type of ventilation your room has[/B]
1 20" Lasko Box fan for intake. A 8-9" circulating fan inside the cabinet and another 20" Lasko Box fan for the exhaust.
The lasko fans supposedly push 3000 cfm at their highest setting.
Now for the problem.
The edges of some of my leaves seem to be indicating that they are having heat stress.
What is confusing is that the temps in my grow cabinet are good as listed above.
I raised the lights an inch and then I took the plants in the 3 gallon pots off their stands (stack of dvd's) to move it even further away from the light until it was 18 inches away.
I then rotated my crop to ensure they weren't all in the same spot and getting hot spots.
Even with my hand placed over a particular leaf that's curling badly I feel no discomfort at all. So I'm not sure that it's a hot spot.
I've started leaving my cabinet door cracked open slightly just incase hot air wasn't escaping fast enough (I doubt air flow is my problem here given my fan setup.)
beyond that my plants look healthy. Here are some pics of the actual problem.
Some strains do weird things, its all about the genetics. Just keep feeding them neuts and keep the pH around 6.2 - 6.8 so the neuts dont lock up, also a balanced pH could be your problem for stress on the leaves. I doubt its the heat.
+Feed neuts every other watering, not only once a week.
+Make sure you wait atleast 15 to 20 minutes before you know for sure what your new pH is once you balance the water!
As for it being the strain. It hasn't done this the entire grow. Weird that it's just starting to do this after 1 week under HPS.
It was previously under CFL's. The growth of the plant exploded under hps and then about 2 days ago or so I saw the edges of the leaves curling upwards and can't seem to figure out the cause now.
Only thing I can think of is.
+Neuts lock up
+unBalanced pH stressing your leaves
Don't use tap water!!!! Go out to the store and buy some distilled water. Or try Zypherhills. Watering could be your major problem I missed that your using tap water.
Flush it, tap water has to many impurities, I grew all organic even up to the bug spray and neuts.
Well I started flushing my plants. I didn't get the initial run off PH but after a gallon and a half of distilled water my ph was 5.9. After 3 gallons of water it 6.4-6.5.
Seems like the PH just kind of crept up on me suddenly.
I'll be drilling holes in the sides of my pot (1 hole each side) to help aerate faster and recover from the flush. I will do one more mini flush later this week (1 gallon or so).
Hopefully this is my problem. I really wasn't expecting the PH to be so low especially considering I just transplanted.
Is this caused by the salt build up I've read about? (haven't read alot on it, just as I'm reading daily threads and come across it)
The curled-up leaves are classic heat stress even though your canopy temps are correct. This is probably happening on the tops closest to the lights themselves, correct? Higher temps also mean lower %RH in that area and that part of the plant suffers. Keep your plants well watered and circulate air very well so that the cabinet temps are even throughout. Bend and tie the affected tops away from the lights.
Random guy, you told the OP to never use tap water, and to use only distilled- this is not good advice when you don't mention that with distilled water you MUST add CalMag, and there are very few situations when a soil grower should not use his available tap water.
The 'impurities' in tap water are mainly dissolved limestone, which your plants need... unless your tap water is known to contain unusually high levels of chlorine, road salt, sulfur, or iron (these are the most common problems with tap water, but still rare for them to be bad enough that you can't use the water), go ahead and use it.
Sounds like the flush was a good idea though, and the extra holes help a lot I've found. Flushing with distilled water is effective, but don't forget to then give a watering with either distilled water + calmag and weak nutes, or tap water + weak nutes.
My leaves have started to uncurl. To answer your questions it was happening to leaves low on the canopy as well as high. Not too many were but it didn't seem to matter where they were located on the plant.
I think salt build up had alot to play in this as I was also seeing the eagle claw leaves and some weird spotting elsewhere. Looks like it was the first signs of lockout probably due to PH.
And yeah I did some more reading and saw a few posts by you that you shouldn't use distilled unless you're using calmag or some equivelant. So I went ahead and just used tap water. I also rinsed off the 2 plants I did in distilled with 1 gallon of tap water each.
Wanna job? Your dead On! The circulation,of a air in that particular area of the room would solve your worries! Relative Humidity. It moves about the room like a Ghost! You can't see it.. But you can surely see the affects of it..%RH..
Actually it was a PH issue. After the flush the leaves went back to normal.
And I have PLENTY of circulation in that room. Check out my grow log for a pic of the cab recently. It has a 20" box fan for the intake pushing at it's highest setting (3000 cfm), another 20" box fan for exhaust at it's highest setting and then like a 12" oscilating fan.
Problem was definitely PH. Although it looked like heat stress it did not seem to be likely to me.
Everything is back on track now.
When you flushed them..... You actually raised the RH in the room. So it was a humidity issue. I stand by that.....:thumbsup:
I'll have to disagree again. My RH was and remains approx ~ 40%. give or take 1-2%.
Even after flushing them my RH did not rise that much.
Not to mention I had multiple symptoms. Leaf edges curling up, random spotting, eagle claw leaves, leaves dying.
I'm just confused as to how you can stand by saying it was a humidity issue when humidity was always within an acceptable range and then when I flushed it you still insist it was a humidity issue.
My soil run off was far below that of what these plants need in order to uptake nutrients in soil.
Even if I had solely just added moisture to the room via a humidifier it would not have resolved my problem.
Potassium is best absorbed in soil from ph 6.3-6.8. My ph was about 5.6-5.2.
In order for the stomata to open potassium is needed. K ions make their way into the guard cells adding rigidity opening the stomata.
Transpiration is also achieved through the stomata.
If the stomata are not opening, or not opening enough due to lack of potassium uptake because of a ph problem then the leaves will not be able to properly release moisture in the air; thus leaving the plant with poor means of cooling itself naturally. The result? Leaf edges curling upwards looking like heat stress when it's really a PH issue.
Imagine if all your pores closed completely on your body. Imagine your nose plugged, mouth sown shut and your erm.. butt corked up as well. Then go stand in a very bright concentrated light where the temperature is about 85-90 degrees. Now throw a box fan in front of you. That box fan would do you no good since your body would not be able to physically release heat from within.
The other symptoms I saw were also due to ph issues. As I saw multiple nutrient deficiency symptoms. Most nutrients are best absorbed in soil at a range of 6.3-6.8 as shown here in this
chart
Had I not had multiple issues happening at the same time I may agree with you, but I'll have to say here that I do not agree with you.
You replied to this post 16 days after I had done a flush. RH wouldn't stay up for over 2 weeks based off 1 flush.
I don't mean to be rude and I am not trying to pick a fight but if you're going to stand by that then I'm going to have to ask you to back your reasoning with something more than reitterating something said by Stinky.
I'm sorry for seeming brash and I'm sure you have loads more expierence than I do but I went through alot of trouble to understand why my plants were having problems and how everything was linked together. If there is an alternative possibility that can be explained from a micro level to the symptom then I'd like to hear it. Otherwise I've already shown that this was not a simple RH issue.
