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Leaves Curling Up


Well-Known Member
Hello all!

I've been lurking for awhile and decided to do my first grow. However, as we all know that usually comes with problems...

Strain - Feminized Northern Lights, Feminized C99
# of Plants - 6 (3 of each strain)
Grow Type - Soiless
Grow Stage - Vegetative
Bucket Size - 3 Gallon
Lights - 1x 300W LED, Separate 104W 4100K Fluoro
Nutrients - Fox Farms
Medium - Soiless Mix (Homemade: ProMix, Pearlite, mushroom compost, with nutrient additives)
PPM - ?
PH - 6.5 - 7.0
RH - 35% to 50%
Room Temperature -75F constantly controlled
Solution Temperature -65 - 70F
Room Square Footage - 3' x 8'
Pests - None Known

Problem: My leaves are curling upwards and growth is very slow.

The leaves are giving the 'taco' curl upwards, as well as some leaves having the edges roll up. It seems there could be several possible issues from my research: heat stress, humidity issues, magnesium/calcium deficiency, too much direct wind, etc. My setup is as follows.

I started 3x Northern Lights on 11/18/14 under the 4100K Fluoro (not ideal I know). Started in Solo cups (no nutrients), upgraded to 1 gal pots (with homemade soiless mix), and finally 3 gallon pots (same mix). Growth looked pretty good, though slow. The larger plants you see in the picture are 2 months old! I put them under a cheap 300W Mars Hydro Light which draws 185W a few weeks ago, and growth has been slow since. I read that growth may be slowed when switching to LED, but I disregarded it. Then I saw curling and attributed it to Mg deficiency, as that was also somewhat correlated to LED use.

I have not fed these plants with any nutrients, other than what was in the soil. The only addition was epsom salt at 1tsp/gal, which I started several days ago, and added some hydrogen peroxide as I had watered not long before.

I also started 3x C99 plants on 12/7/14 and the two in 3 gal pots did well, but I over-fertilized the one in the 1 gallon pot and growth is finally catching up. These plants seemed to be growing quickly, but slowed recently, about the time the leaves started curling. I transplanted the two that were curling into 3 gal pots 3 days ago, and began LST. They were also moved under the 4100K Fluoro, as I would like to start flowering the plants which are under the LED, and keep these (as well as some clones) in Veg.

Some of the plants look like they may have a nitrogen deficiency, but I don't want to over-fertilize. I am also concerned about over-watering, as the pots have not been drying out very fast at all. It is possible I may have some root rot, I supppose, but dont' know how to check for that. I also have an oscillating fan in the room, but it blows over the tops of all plants, so I wouldn't think wind burn would be an issue.

Things I've changed since the curling began:
-Made a controller to keep a constant 75F all day. Should I try to lower this at night?
-The controller also runs a humidifier, with a shutoff at 50% RH. The whole growth has been at 35-50%, as it is winter here and hard to balance humidity/airflow.
-The controller also runs the vent fan for 1 minute every 5 minutes. This should give me a whole air exchange every 5 minutes. Is this good?
-Added a larger humidifier. I would think this would help, but who knows!

Below are the pictures. You can probably see the difference between the strains, but the NL pictures are first, with the younger C99 pictures being last.

Thanks for the help ahead of time!



New Member
Looks like nitro deficiency in the making. I would start them on half strength dose of nutes and full strength dose of cal/mag, and go from there. And the leaf taco is probably heat related. Get a small fan to blow gently across the tops


Well-Known Member
I went ahead and watered all plants with the following (as they are all 6-8 weeks old):

3 tsp/gal Espoma Garden Lime (contains Calcium and Magnesium)
2 tsp/gal Fox Farms Grow Big (also contains Magnesium)
1 cup/gal Hydrogen Peroxide
balanced to 6.5 pH

I used the lime as I couldn't find a CalMag nutrient at my local nursery.

When I took a closer look at some of the leaves, I saw some speckling discoloration as well as a few 'rust spots' both indicative of calcium deficiency (from what I could find).

And the leaf taco is probably heat related. Get a small fan to blow gently across the tops

I'm still pretty sure I don't have any heat stress though. The problem started when I had the plants under my LED light at the recommended 18-24" (I was around 24"). I recently moved 2/3 C99 plants under the T5 fluoro, but they are at about 2" from the bulbs. Plus the fan blows all around the room, at about the tops of the plants.

Is it possible that 75°F is too hot for these girls?


New Member
I agree lower the ph. You could be seeing nutrient deficiencies even though you've added the nutes because it's not available unless the ph is correct. That along with keeping the humidity at 50% and you should be good. 75° is a good temp. Vegging plants can handle up to 85° even though I wouldn't recommend it. I would drop the temp to 70-71 during lights off.


Well-Known Member
Stealhboat and dkellz are spot on lower ph with pro mix
I run 6.2 all the time unless my runoff is going way up/down then I will go to 6.0(if runoff creeps up)-6.4(if runoff goes down) pro mix can run at 5.8-6.5 but are ladies seem to like it at 6.2


Well-Known Member
Thanks for your help guys, I'll shoot for a pH of 6.2! I originally was using 7.0, which seemed to work well, then lowered it to 6.5 to prevent some nutrient lockouts, but didn't know I should go so low. It makes sense though, as the one plant in Fox Farms Ocean Forest seemed to keep going strong after the other nutrient problems. It still showed some deficiencies, but the runoff was around 5.8 usually.

Anyway, the plants all look better. The C99 plants have fully recovered, and no more curling. The color cleared up on the yellowing plant, but I'm still having some curling on one of the taller plants. Maybe time will tell, and I found an organic Cal/Mag nutrient I'll start using for each watering now.

I have another issue now, though. I'm almost 10 weeks into veg for the Northern Lights, and 2/3 plants are showing some preflowering. These were the plants that weren't doing well, but I'm not sure why they'd start flowering under 18/6 LED lighting! The plant in the Fox Farm mix isn't showing signs, so could they be stressed by nutrient/pH issues to flower?

I was planning on flowering as soon as I fixed my nutrient problems, so the timing is fine, but I wanted to check for future grows. I have healthy clones of all plants, and I'm pretty sure they aren't autoflowers because of the 10 week veg time, but maybe you all can help me!



Well-Known Member
I appreciate all the input guys. I think this is mostly a pH problem as I'm having trouble with adjusting my pH of my veg plants. I'm using tap water, pH'ed to 6.2 with vinegar (I'm cheap), but after flushing with 10 gallons (they are in 3 gallon pots), my runoff is still at 7.8 - 8.0. I'm thinking this could potentially be thrown off because of my cheap pH meter (digital one seen here). The runoff is still a dirty looking brown, and this is my first thorough flush for these girls. I've read that some growers don't even measure runoff, but it only makes sense that it is an indicator of soil/soiless pH.

My mix only had ProMix, pearlite, mushroom compost, lime, Espoma 'Plant Food', bone meal, and blood meal. I typically water with at least 10% runoff. I don't know what would be keeping it so high and dirty colored though!


Well-Known Member
So I found out that my vent fan has not been operating at all, possibly for the last 1-2 weeks, which could have contributed to the problem. I replaced it, and the air feels much cleaner. Humidity is still around 50%, and temperatures are 75-78°F.

I did some testing and determined runoff from all plants (except the fox farms plant) was anywhere from 7.5 to 8.3, WAY out of range. I tried flushing and flushing, with 6.3 water (I even broke down and bought some pH down). That didn't help. Somehow I have a very basic mix. So I decided to take drastic measures and flush with a fairly high percentage vinegar solution to drop the pH. It took a lot of flushing, but I was able to get all the runoff into the 6.2-6.5 pH range. I then flushed with 6.2 pH water directly after the vinegar solution. After 2 days, they don't particularly look any worse than they did, but I'm hoping I didn't destroy the root system. All the plants have very soaked medium, so it's going to take some drying out time before I can re-fertilize and get them back on track. I know it may take them a few days to recover from this huge pH drop. Any suggestions are welcome.

Also, I'm still getting the curling/tacoing on a lot of the plants, and it's come back in some cases. I did get a TDS meter, and tested my tap water. It comes in at around 340 ppm, which I understand is quite high. This leads me to believe I shouldn't have a Cal/Mag problem, but I could be wrong.

Has anyone had any issues like this? If so, how did you solve them?


Well-Known Member
To add some closure to this thread, I believe it was all due to a pH issue. I bought a new pH meter, and it turns out my old meter is now a piece of crap. This was likely due to improper storage. Let it be a lesson - store your pH meter properly! Some require a potassium chloride solution and some are OK to store in distilled water. Don't just rinse it off with tap water and put the cap back on!

So now that the pH issues have been resolved, the plants are looking pretty healthy, even though some of the lower leaves didn't recover.


New Member
iif been having this problem with my plants heat isn't to hot an heaps air flow iv pulled light away from them an all new growth is curling real bad an its happening to 5 of my babys could it be bugs iv gave them epsom salts an kelp notes an iv flushed them still no change day 5
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New Member
Iv been having problems with curling an dont no what's going on can some one help me out an tell me what's going on its happening to 5 of my plants could it be bugs


Well-Known Member
Welcome to the forum. We need to know what lighting, grow media, nutrients used and when, the pH of your nutrients, and a picture under normal lighting to help you. This is a very old thread. Start by going to the Introduction section and say hi there with more info


New Member
I'm growing under 400w hp sodium light dimmable to super lumens an iv used thrive an super thrive epsom salts to organic seaweed an blood an bone an fish an sea weed groth booster use them at different times some together bout couple days ago an iv flushed them all no change an PH is at 6.2 6.5 6.6 an
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