Day 37 of flowering, is this red fan-leaf discoloration a problem for my 3 Indica SCROG?

Hi there,
This is an indoor grow under approximately 800 Watt of actual lighting power LEDs (3 cheap units daisy chained together consumes about 800W in total). I am getting ~50 000 Lux (according to a cheap Pyle Lux Meter) directly under the largest of the 3 LEDs which should be enough for an Indica(?), and that is where the reddish leaf discoloration started. I don't think it's leaf burn as it does not look like examples I have seen before. Starting week 6 of flowering, and so far I have not seen a single discolored leaf, until 1 week ago when I started seeing some yellowing leaves drooping off under the canopy. I then noticed the distinct red discoloration under the largest cola in the canopy (in the photo).

I am growing in a 4x4 foot SCROG and the screen is pretty well filled in. It's fairly dark underneath, so I was not too surprised to see some yellow leaves. I am growing 3 indica plants in organic "super-soil" type mix with plenty of slow-release fertilsers and good drainage and aeration (lots of peat, perlite). I am also supplementing with cheap Dr. Schulz 10-15-10 liquid synthetic fertiliser with additional micronutrients (iron, manganese etc. ) to supplement the organic soil...Basically this has been a really good grow so far and it's only these few discolored leaves on 1 of the 3 plants that worries me, as I think it is starting to appear on other fan leaves too.

I thought it could just be old age, senescence, in which case no cause for alarm, but I don't want to take any chances so please have a look and let me know what you think, if you have any experience of something similar. Cheers

After 5+ weeks into flowering I'd say that seeing leaves displaying color like that is probably just a trait of that strain. Looks really good!

Yeah , seems to expressing a trait ....

However ..... Me things you got bugs ... Speckling on leaf .
Plus leaves are hella dark , you should be on a P / K bloom with LOW NITROGEN.
(BLOOM nutes ) with lower nitrogen ....

Thanks for the info guys. I will go check for bugs Budzbuddha (respect the name). I know I have some fungus nats in there as I have about 40 trays of various seedlings on the go and there is a LOT of moist soil in the area. Would they cause speckling? I thought they were fairly innocuous as they do not actually drink/eat from the plants, but I guess they can carry mold spores and other crap between leaves. B*stards.

Regarding "hella dark" leaves: I thought I should probably invest in some proper Bloom nutrients but I have spent a lot so far on this setup so I was trying to save a few bucks... false economy perhaps. Also I thought green was good - this is only my second grow so I got a lot to learn I guess! I shall pop down to grab some proper Low Nitrogen, High PK nutes this morning and see if it has any effect.

Update, many leaves in the canopy above the screen are now exhibiting this discoloration. Distinct yellowing along the lines of the ridges of the fan leaf, and dark red/brown covering the top of the leaf between ridges. Take a look in this picture:

Update: no bugs except fruit flies (fungus nats). Have 20 Gallon pots which should act as a buffer against minor imbalances in nutrients supplied through watering/feeding. This makes me think it's not related to nutrients as the other 2 plants in the grow are fine, except maybe a little too green as Budzbuddha noted.

Now I see that the yellowing is occurring around the leaf margins, so maybe it COULD be light burn.... It is occurring just under the most powerful light's centre, where it overlaps with the beams from its neighbours.

Maybe it's some leaf burn (yellowing), coupled with a trait expressing itself (the red/brown areas) combined with an excess of Nitrogen (foliage TOO green for flowering - thanks Budzbuddha). It would be nice to know so I can correct this for the next grow, coming right up in, let's see, 3 weeks!

Whats your PH?

Also it s a MYTH, that weed needs LESS Nitrogen in flowering.

Going by Chem Gro....... Tissue Samples........ weed needs nitrogen through the complete growing process, in increasing amounts.

Also going by tissue samples Potassium should be 2x that of Nitrogen.
19.5 Nitrogen x 39 Phosphorus. 20 Potassium.

jimihendrix1 said:

Whats your PH?

Also it s a MYTH, that weed needs LESS Nitrogen in flowering.

Going by Chem Gro....... Tissue Samples........ weed needs nitrogen through the complete growing process, in increasing amounts.

Also going by tissue samples Potassium should be 2x that of Nitrogen.
19.5 Nitrogen x 39 Phosphorus. 20 Potassium.

Click to expand...

You said it right but then put high phosphorus instead of potassium.

Here is an interview with the president of dyna Grow sharing his results. Which are pretty much like you say here. He adds calcium is consumed in higher amounts than phosphorous and nitrogen is needed all the way through. He also shows a need for silica. But that needs added in hydro not so much potting soil.

That's some good info. I could listen to this guy all day. I'm already on board and my Dynagro plants make the rest look wimpy.

PH is about 7, but I am not sure how accurate the little meter I have is.

It's a little too alkaline. Could this be perhaps because I added in too much dolomitic lime to the base peat?

danmac0710 said:

PH is about 7, but I am not sure how accurate the little meter I have is.

It's a little too alkaline. Could this be perhaps because I added in too much dolomitic lime to the base peat?

Click to expand...

Those probe meters always show 7 for me. A reliable probe type ph meter costs hundreds of dollars to thousands.

Look up slurry method to test soil ph or at least water to runoff and see what comes from the runoff.

But yes. If you added extra lime you can push the ph up to a stable 7 instead of mid to low 6’s where it belongs.

Most pre mixed potting soil has the right amount in the bag.

MichiganMedGrower said:

You said it right but then put high phosphorus instead of potassium.

Here is an interview with the president of dyna Grow sharing his results. Which are pretty much like you say here. He adds calcium is consumed in higher amounts than phosphorous and nitrogen is needed all the way through. He also shows a need for silica. But that needs added in hydro not so much potting soil.

Click to expand...

The Calcium Nitrate in the Chem Gro is also 19% Calcium, and 15.5 Nitrogen.