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Bacterial leaf spot? Too high EC?

Hi there. I'm growing plants under 2 54w t5 lights in coco coir. They're fed every 2 to 3 days when the coco gets dry on top. Today I noticed some black spots/ tears on two plants.


Could this perhaps be bacterial leaf spots? My other smaller plants are fine and there is a similar sized chocolate
Bhutlah doing fine.




My theories are that it could be bacterial leaf spot, the ec could be too high or maybe some water was spilled onto these two plants somehow causing them to burn. They're in a room with no insects and it is not too humid in there. There is a small fan blowing on them constantly.

Does any one have any ideas? I don't want them to die =(
 

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They look fine to me. Definitely don't see any signs of bls. Do you have them in straight coir? Feeding every couple of days seems excessive otherwise. I dont generally start feeding mine until they have 6-8 sets of true leaves.
 
Also, you want the top couple inches of soil to stay dry to prevent overwatering, fungus gnats, and other problems. The top can be dry and still be soaked on the bottom.
 
Thanks for your reply. They are in pure coco coir which has been sieved to remove the fine coco.

Because the coco is so coarse it dries out quickly. In the higher resolution photos it looks like it could be nutrient burn so I might try bringing them down to 0.6 ec or 300ppm. Perhaps 500 ppm is too much for plants this size.

Would you suggest watering from the bottom only?

In the higher resolution photos there are black spots especially on the bottom photo and I can't figure out the cause of it. Maybe I'm ovdrthinking?
 
CMJ said:
Yes, maybe bottom water and let them be...
 
OP says he has a coarse mix, with the fine pith sifted. I'm not sure if that will make for the best wicking mix.
 
Keep the EC on the low end.  Water ONLY when necessary, and maybe even still let every 6th or 7th watering be straight (no nutes), until you actually get a good showing of leaves.  
 
Don't bottom water only. You want to water from the top at least periodically to flush out the chemical salts that otherwise accumulate. When you do a "flushing" watering, water with a light fertilizer solution (not regular strength, but not only water) and pour through from the top until a reasonable amount flows out the bottom.
 
To me it looks like you had some minimal transpiration issue during leaf formation, but if so we're talking incredibly minor and largely unavoidable. Significant concerns will generally be much more noticeable or last over time.
 
Thanks for your responses and much needed reassurance. This is probably a case of helicopter parenting.
 
I will lower to EC back to 0.8 which the plants responded well to. They probably don't need to be fed any higher until roots are coming out the bottom of the cups.
 
With how fast the coco coir dries out I can see very minute amounts of salts accumulating on the top. Top watering seems more ideal to counteract that especially because only the top is visible.
 
It's hard to see into the coco coir and tell if it has salt all throughout it but to be safe let us assume it does accumulate. Ideally every feeding will flush out some of the salts so long as there is run off (which there always is). The salts on the top actually get dissolved each time the plants are fed.
 
I feel uneasy about giving coco coir pure water because of cation exchange capacity. Perhaps a diluted calmag solution may be a better option The coco coir drains very fast when it's sifted so flushing the plants even with 250mls of water would only take 30 seconds or so to drain out so after each plant could be fed nutrients again directly after flushing.
 
Again, thanks for the help, it is much appreciated.
 
You shouldn't grow in straight coir unless you are using drip irrigation several times per day - it doesn't retain water or calcium very well at all. I use a mix of 70% coir, 20% vermiculite and 10% perlite for both seedlings and outdoor growing. I do recall reading it was either vermiculite or perlite that is able to retain some calcium, which is a very good thing.
 
If I lived in a hotter climate, I'd most likely use 60% coir, 30% vermiculite and 10% perlite. Even up to 40% vermiculite for extreme hot / windy climates, reducing the coir to 50%.
 
podz said:
You shouldn't grow in straight coir unless you are using drip irrigation several times per day - it doesn't retain water or calcium very well at all. I use a mix of 70% coir, 20% vermiculite and 10% perlite for both seedlings and outdoor growing. I do recall reading it was either vermiculite or perlite that is able to retain some calcium, which is a very good thing.
 
If I lived in a hotter climate, I'd most likely use 60% coir, 30% vermiculite and 10% perlite. Even up to 40% vermiculite for extreme hot / windy climates, reducing the coir to 50%.
 
Not that I disagree with the using of straight coco coir - I normally wouldn't.  But there is nothing wrong with the way the OP is doing it.  (since it's been sifted)  I like your mix better, but in the right conditions, coarse coco produces some pretty phenomenal results.
 
As far as coco not retaining Calcium, it's quite to the contrary.  The cation exchange of coco is such that when you buffer with calcium, you will release Nitrogen, Sodium, and Potassium.  Calcium will attach to coco coir more than possibly any other nutrient - except for when Calcium is deficient.  Then, it starts locking up Nitrogen, Sodium, and Potassium.  That is one reason why early coco coir growers had such problems with salt content.  Before the calcium charging was well understood.  The charging is essential for releasing the Potassium, specifically, but has the added bonus of purging excess sodium. (which was often a resultant of salt sea water)
 
This is why you MUST either pre-charge coco coir with calcium, or buy a product that has already been charged/buffered. 
 
I also should have added that if you are measuring a significant runoff of Calcium in your nutrient solution, then it's because the media is already buffered to full capacity.
 
solid7 said:
 
Not that I disagree with the using of straight coco coir - I normally wouldn't.  But there is nothing wrong with the way the OP is doing it.  (since it's been sifted)  I like your mix better, but in the right conditions, coarse coco produces some pretty phenomenal results.
 
As far as coco not retaining Calcium, it's quite to the contrary.  The cation exchange of coco is such that when you buffer with calcium, you will release Nitrogen, Sodium, and Potassium.  Calcium will attach to coco coir more than possibly any other nutrient - except for when Calcium is deficient.  Then, it starts locking up Nitrogen, Sodium, and Potassium.  That is one reason why early coco coir growers had such problems with salt content.  Before the calcium charging was well understood.  The charging is essential for releasing the Potassium, specifically, but has the added bonus of purging excess sodium. (which was often a resultant of salt sea water)
 
This is why you MUST either pre-charge coco coir with calcium, or buy a product that has already been charged/buffered. 
 
Yeah I read something interesting regarding this and perlite or vermiculite effects, but for the life of me I can't find it anymore.
 
I buy the Canna Professional Plus coir which is already buffered and have had outstanding results with it - I have so many pods hanging off my plants now I won't know what to do with them all! 
 
podz said:
 
Yeah I read something interesting regarding this and perlite or vermiculite effects, but for the life of me I can't find it anymore.
 
I buy the Canna Professional Plus coir which is already buffered and have had outstanding results with it - I have so many pods hanging off my plants now I won't know what to do with them all! 
 
I can tell you that if you live in a humid climate, you don't really want to use vermiculite.  It retains moisture.  But it also retains nutrients, so it's really good stuff for a dry climate.  I use biochar here, instead of vermiculite, in either case.  Perlite is still the king, for me, when it comes to drainage.  I haven't found a substitute yet that does such a balanced job of draining while retaining good useable amounts of moisture.  I've not really heard about perlite retaining any nutrients.  But who knows...  
 
What I can say, is that if you're using coco coir, you'll want to be careful about using "bloom" nutrients with mega doses of K, because K in coco will do actually undo the calcium, and lock out the aforementioned cations. (including itself)
 
Any premium coco product will be buffered, and like you say, great results.  I have almost totally switched over, because it lasts longer, and doesn't compact like peat.  Peat has some humic and fulvic acids that are lacking in coco, but that's a super easy amendment.
Glad to hear someone else is growing in it.  
 
Here is a good article that shows how using Canna A+B, which I am using, works so well together with coir:
 
"Canna Coco A&B have been designed to work with Canna Coco Pro Plus so that no separate grow and boom versions are needed. This is achieved through making use of the Calcium buffering process inherent in the coco. Coco A&B has higher levels of calcium in than regular nutrients. As you increase the EC into the flowering period, the elevated levels of calcium exchange themselves for potassium within the solution surrounding the coco fibres. So essentially you create your own flowering nutrient ‘inside’ the coco itself."
 
https://www.groworks.co.uk/product/canna-coco-professional-plus
 
solid7 said:
 
I can tell you that if you live in a humid climate, you don't really want to use vermiculite.  It retains moisture.  But it also retains nutrients, so it's really good stuff for a dry climate.  I use biochar here, instead of vermiculite, in either case. 
 
I live in a relatively humid climate but I also sometimes only water my plants once per week as they are in 30 litre containers where there is 6 liters of vermiculite. I fully intended them to be in direct sunlight 19 hours a day and only need watering once a week because with my deck building project this summer it was impossible to setup the normal drip irrigation system. NOTE that this strategy doesn't work so well in the 12 litre containers which I am using for some of my plants.
 
podz said:
Here is a good article that shows how using Canna A+B, which I am using, works so well together with coir:
 
"Canna Coco A&B have been designed to work with Canna Coco Pro Plus so that no separate grow and boom versions are needed. This is achieved through making use of the Calcium buffering process inherent in the coco. Coco A&B has higher levels of calcium in than regular nutrients. As you increase the EC into the flowering period, the elevated levels of calcium exchange themselves for potassium within the solution surrounding the coco fibres. So essentially you create your own flowering nutrient ‘inside’ the coco itself."
 
https://www.groworks.co.uk/product/canna-coco-professional-plus
 
Yep, so there we go.
 
I actually haven't used this product, or read any labels.  I have been using coco for a long time, and had to find out by trial and error, and lots of deduction.  Believe me, I killed a few plants. LOL
 
So flushing with Ph'ed tap water should be fine?
 
Here is how they look 1 and a half days later.
 
The caramel bhutlah is starting to green up a bit but it's still yellow in patches.
 
bAnyRcA.jpg

 
The lemon drop looks very pale on the new growth.
 
S0fkGN9.jpg
 
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