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Coco - burnt leaf edges + spotting

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searchingforit

Member
I always get this 3-4 weeks into flower. In combination with this pistils begin to die back and flower/terpene production is limited. Coco mix feeding any of the major coco nutes in RO water @ every pH from 5.6 to 6.2 this still occurs like clockwork. It begins with burnt leaf tips, goes to the edges and by week 5-6 all sun leaves are affected. They will point downwards and become very brittle. Branches are brittle as well. Lighting is 600 watts. EC does not go above 1.4 hand watered once a day. I will point out the first 3 weeks of flower the plants look perfect.

The tops begin to become very dark green so you think it's overfeeding and dial back but I have gone as low as .9 EC of an appropriate coco nute (which ratios follow a full strength 150-50-200 NPK with 150 ppm calcium + 70 ppm mg) and this deficency or burning continues at these low EC readings. The plants closest to the light progress fastest so I think it's a deficiency. Seems like K def but the rust spots throw me off. The next step after this picture in progression is for the rust spots to connect in between the leaf veins forming a solid brown spot on leaf margin.
 
T

TanzanianMagic

Well-known member
Veteran
searchingforit said:
Coco mix feeding any of the major coco nutes in RO water @ every pH from 5.6 to 6.2 this still occurs like clockwork.

The tops begin to become very dark green so you think it's overfeeding and dial back but I have gone as low as .9 EC of an appropriate coco nute (which ratios follow a full strength 150-50-200 NPK with 150 ppm calcium + 70 ppm mg) and this deficency or burning continues at these low EC readings.
Click to expand...

- The R/O water causes magnesium deficiency.
- The green leaves are caused by magnesium deficiency.
- Not all cal/mag sources are readily absorbed by plants.
- Keep the EC an even 6.0 when feeding.

I used to have a problem with magnesium deficiency in r/o water and coco or light mix, when using Cal/Mag which smelled like it was made from bonemeal. Now, I use a constant 0.1 EC of epsom salt.

However the biggest change I've made is stop using R/O filtering.

What I do, is let any tapwater I'm going to use stand in a watering can or reservoir, near the plant, for at least 3 or more hours.

This means the temperature is the same as the plants, and the chloride has a chance to evaporate.

There is a lot of calcium and magnesium in the water.

This problem shows up during early flowering, because that's when the plant needs more magnesium and phosphorus.
 
S

searchingforit

Member
I use RO and add cal/mg back properly. I have not seen Mg def manifest in this way - starting with burnt leaf edges and extremely dark leaves. My understanding of Ca:Mg is you typically will have a def of one of the other. With my nutrients I have approx 150 ppm ca and 60-70 mg or a 2.5:1 ratio which shouldn't cause a def if it isn't locked out due to pH.

The premature dying back of pistills is interesting as I see that (other than broad mites and pollenation) in pictures with +Nitrogen toxicity.
 
T

TanzanianMagic

Well-known member
Veteran
searchingforit said:
I use RO and add cal/mg back properly. I have not seen Mg def manifest in this way - starting with burnt leaf edges and extremely dark leaves. My understanding of Ca:Mg is you typically will have a def of one of the other. With my nutrients I have approx 150 ppm ca and 60-70 mg or a 2.5:1 ratio which shouldn't cause a def if it isn't locked out due to pH.

The premature dying back of pistills is interesting as I see that (other than broad mites and pollenation) in pictures with +Nitrogen toxicity.
Click to expand...
My guess is she just needs a little more magnesium in flowering.

https://www.icmag.com/ic/album.php?albumid=80582&pictureid=1963004

I presume you've already checked run-off to see there is no buildup of nutrients. If that's ok, then...

Magnesium is one of the most common deficiencies in cannabis, because it regulates the chlorophyl which makes the leaves green. The calyxes of the buds are tiny rolled up green leaves, hence the plants need even more magnesium during flowering.
 
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S

searchingforit

Member
You still think the same? Here are more pictures. Happens around the same time in flower (25ish days). Pistills die back and brown premature. These haven't been fed higher than 1.4 ec, which I dialed back.
 
R

rjrom90

Active member
Could be Ca/P lockout from calcium phosphate precipitation. Watering once per day may not be enough to keep the phosphorous in solution which allows it to react with calcium to form calcium phosphate. If watering multiple times per day isn't possible, try a microbial inoculation like Mammoth P to break down the calcium phosphate for plant availability.
 
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TanzanianMagic

Well-known member
Veteran
With the better lit pictures...

It looks like a Potassium deficiency/lockout. And the leaves still look very dark green, so do need a little extra magnesium (0.1 EC of epsom salt is enough if you use unfiltered tapwater).

The dots on one of the leaves could be either calcium deficiency or insect damage.

So it would still be helpful of having a closer photograph, including of the underside of the leaves.
 
Vash

Vash

Ol' Skool
ICMag Donor
Veteran
Do you get runoff every time you water, and if you do have you checked it?
 
S

searchingforit

Member
Vash said:
Do you get runoff every time you water, and if you do have you checked it?
Click to expand...

Yes, I handwater and get a lot of run off. I've also used drip clean with every watering. Cut that out when trying to diagnose. Doesn't matter how much run-off I put through. I'm either overfeeding or underfeeding IMO. I've tried everything from 1.6 down to 1.0. I had this same problem when I was drip watering 4 times a day using 6/9. Every single time. Great growth in veg up to 3-4 weeks in flower. I notice a few brown pistils and this snowballs. Tips look burnt a few days later, then leaf edges. It snowballs. Buds do not swell or stack much after this begins. Smell is not there and so on.
 
Vash

Vash

Ol' Skool
ICMag Donor
Veteran
What I mean by "checking runoff" is have you checked the EC of the runoff? I'd also agree on the overfeeding. Underfeeding gives you a different look - a pale green of sorts. I'd check the EC of runoff first. If EC was acceptable, I'd let the medium dry out a bit before feeding again. If runoff is high, I'd only water until the EC is in an acceptable range. Good luck with it.
 
S

searchingforit

Member
Feeding at 1.4 run off was 1.8 when things went south which means they weren't eating so I dialed back to 0.9/1.0 ec and the damage continued. Going to scrap this crop and try again.
 
PurplePotion

PurplePotion

Member
searchingforit said:
Feeding at 1.4 run off was 1.8 when things went south which means they weren't eating so I dialed back to 0.9/1.0 ec and the damage continued. Going to scrap this crop and try again.
Click to expand...


Yikes, bad enough to scrap it all? I’ve noticed a little bit of the same issue in terms of the rust/burning on the edges, but it seemed to grow out of it after a week or two, definitely not bad enough to scrap it. I believe mine may have been heat related, any chance you’re having trouble controlling the environment? Any signs of bugs? Just some thoughts. Let us know what you figure out, that would drive me nuts. Good luck ! :tiphat:
 
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