Requesting advice about some leaves turning a little yellow, tips curling up

M

Maurice66

New Member
Hi- I'm wondering if someone could give me some advice about a single plant in my budding grow room. Several of its large fan leaves and a few smaller leaves near the top of the plant have in the past week started turning a little yellow in irregular splotches and the leaf tips have curled upwards. The buds appear totally unaffected. The plants theoretically have about 6 weeks to go before harvest. I read elsewhere on this 420 forum that those symptoms indicate heat stress. I have pulled the plant away from the light to give it a little relief (closest part of the plant is 40" from light) - but leaves remain curled. Not sure yet if more leaves are still getting blotchy.

Grow room specs: 12/12hr light period w/single 1000w hps light about 27" from plant tops, temp range 65-78 degrees normally- max temp has been 85 for short periods; humidity range 45-65, usually in higher part of that range- mid 50's, low 60's, ventilation comes from oscillating fan running 24/7 on medium speed with new air coming into this small (20x30') light-tight barn from open window 10' from grow area. Grow room is in a 8x8" corner of the building open to the rest of the interior.

2 questions: I'm growing one each of several strains and this one - romulan grapefruit - is the only strain whose leaves are turning yellow. Is that unusual? All the other plants look great. Is it possible this particular strain loses its fan leaves during budding earlier than the other strains or is this strain just particularly sensitive to heat?

Any advice would be appreciated! Thanks!!
 
Thanks very much for the response and the suggestion- see photos embedded below....

Again, this is only happening with some of the upper fan leaves on a Romulan Grapefruit plant- no other strains have any yellowing and all look great!




RG_Splotches_1.jpg





RG_Splotches_2.jpg
 
To me, it looks like either calcium deficiency or heat stress or both.

What are your temps?
What is the humidity?
What are you feeding it?
pH of water?
Strength of nutrients (dilution)?
Veg or Bloom?
Type of light?
Air circulation?
Do you use intake/output fans?
 
Thanks for the response! As mentioned in original post:

Budding grow room specs: 12/12hr light period w/single 1000w hps light about 27" from plant tops, temp range 65-78 degrees normally- max temp has been 85 for short periods; humidity range 45-65, usually in higher part of that range- mid 50's, low 60's, ventilation comes from oscillating fan running 24/7 on medium speed with new air coming into this small (20x30') light-tight barn from open window 10' from grow area. Grow room is in a 8x8" corner of the building open to the rest of the interior.

Additional info:

Feeding Medi-One 1x/week @ the recommended 25 ml/gallon dilution
Water pH- don't know.

The several strains I'm growing are all growing under the same conditions yet the RG is the only one with yellowing leaves. This is what's confusing to me.

Thanks again!
 
Woops, sorry I forgot to check the OP.

You might try adding cal-mag to your nutrient solution. I'm fairly certain that it's a calcium deficiency. Do any of the other plants have spots like this?:
calcium_defiency.JPG
 
iwltfum- I'm going to have to give you a hard time about reading posts more completely! :;): I've mentioned in each previous post the yellowing is only happening on the one Romulan Grapefruit plant- not other strains. This is the main reason I'm confused....:thedoubletake:

Kidding aside, sounds like good advice to investigate a possible a calcium deficiency.

Any additional thoughts?

Thanks again and I hope you're okay with a little good-natured ribbing!
 
I agree with Iwltfum & Jojo, it's calcium or pH issues. You want to mix up your nutrient solution first and add all supplements if you use any and then pH the nutrient solution to 6.5 pH for soil. You can take some of the run off water and capture it in a cup to test the pH to see what it is in the root zone.
 
Get the PH levels right, that will take care of all deficiencies. If you try adding stuff... it will get worse. However that looks like heavy overfertilization.
 
Maurice66 said:
iwltfum- I'm going to have to give you a hard time about reading posts more completely! :;): I've mentioned in each previous post the yellowing is only happening on the one Romulan Grapefruit plant- not other strains. This is the main reason I'm confused....:thedoubletake:

Kidding aside, sounds like good advice to investigate a possible a calcium deficiency.

Any additional thoughts?

Thanks again and I hope you're okay with a little good-natured ribbing!
Click to expand...

Haha not a problem. I actually did read that part, I just wanted to make completely sure that nothing minor was going on with any other plant that you may have over looked. It's an interesting problem, since it is only happening to one plant. What's different about that plant compared to the other ones?
Position under the light?
Do you water this one first every time you water, or last?
How does the medium dry out relative to the other ones?
Does it have a fan blowing directly on it all the time?
Anything else that might be different?
 
MrRudeSnowman said:
Get the PH levels right, that will take care of all deficiencies. If you try adding stuff... it will get worse. However that looks like heavy overfertilization.
Click to expand...

Oftentimes, certain lines of nutrients don't include enough calcium and magnesium for whatever reason. If it is a calcium deficiency, then your pH could be correct and the plant might still need calcium. You could be burning your plants with too much phosphorus, but still be deficient in calcium, and adding calcium in that situation, wouldn't cause the burn to get worse.

Rudesnowman is right though, you probably should check your pH if you are having problems like this and he's also made a good point that it could be nute burn as well. I'm not familiar with the nutes you are using, but the full strength recommendation on the bottle might be too much.
 
I tested our water pH today and it turns out our water's more basic than the plants apparently like (pH at about 8-8.5 and I understand the plants want something in the range of 6-7- right?).

I tested the water again with the Medi-One nutrients dissolved in it (approximate dilution) and the nutrients drop the water pH to about 6.

So since I've been feeding the plants once per week with a solution apparently at about 6 pH, and watering with no nutrients once per week with our well water at about 8-8.5 pH, perhaps the pH going back and forth is not so good for some strains? Remember this issue is about the leaves getting splotchy and curled up on one plant- one particular strain- the others look great (although a few of the leaves on one of other plants/strains are showing signs of what I understand is over-feeding- see below).

I tested the water draining out of the bottom of the "problem" plant's pot after flushing the soil this morning and see that the pH is the same at our water's pH- 8-8.5.

I'll get some "pH Down" and make sure the water pH levels are where they should be when I water and feed the plants. I'll also lower the amount of Medi-One I'm using in my nutrient additions to make sure I'm not over-feeding the plants. Another plant just yesterday started showing yellow leaf tips even though I've been carefully following following the manufacturer's dilution recommendations. These symptoms look entirely different than the other plant's leaf curling and yellow splotches.

All of this is somewhat confusing since none of this happened to the plants I grew last year using the same water source. This year's effort is different in four possibly important ways (?):

1) Last year I grew three strains outdoors 100% of the time (but suffered at the end with a bud mold attack);

2) This year I'm growing a couple additional strains- last year's strains look great and it's the new strains whose leaves are yellowing and tips curling upwards.

3) Last year I used a once/week Miracle Grow solution to add nutrients to the plants which I now know is a no-no. But the plants/buds looked absolutely fantastic until a few of the buds got the mold right at the end; and

4) The potting soil I used last year was an all purpose "Turf King" soil with fertilizer added bought at a regular garden center, while this year I'm using Roots Organics Potting Soil recommended by a friend who grows cannabis.

Any thoughts on any of this would be very helpful as I try to refine my growing techniques!!

Thanks again for all the advice and suggestions so far!
 
You are on the right track buddy!

Runoff water will change pretty slowly to desired PH levels, wait for soil to dry an flush again.

Check the soil's PH level and nutrients. By the looks of it your soil is good to go through the whole process. Not sure you should use any additional nutes. Maybe at the very end - this is the big secret of having huge yield... folks always fertilize to much and that is a killer.

Another thing - i use phosphoric acid to lower PH. Works perfectly and it's cheap.
 
MrRudeSnowman said:
Another thing - i use phosphoric acid to lower PH. Works perfectly and it's cheap.
Click to expand...

Off subject, but I was curious about where you get your phosphoric acid? When I run out of pH down, that's what I plan on getting, as pH down is made of dilute phosphoric and citric acid anyway. It's good for other stuff too, I just didn't know where to find it!
 

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