New to coco

[u/Accidental_Ballyhoo]

Hey all,
I’m guessing a cal/mag deficiency and possible light stress? Can you steer me in the right direction?

Canna coco/perlite mix 50/50 3 gal pot wicking pots using GH trio, with cal mag ~500 ppm. Plant is 5 weeks old.

[u/Jolly_Yellow5354]

Okay, so definitely Magnesium issue here. I see people recommending adding more calmag, but let's take a step back first and understand what could be causing this.

So obviously a lack of magnesium, but this can be caused by a few things.

Firstly, your pH could be off. If it's below 5.7, your magnesium binds tightly to the water and has poor exchange. Above 6.2, also struggles to uptake.

Next, is too much calcium. Calcium, magnesium and potassium are all cations. Because cations have similar absorption methods, an excess of one competes with the others. Calcium and Potassium are significantly more dominant than magnesium. So if these get too high, the plant can't or very much struggle to absorb the magnesium. This is a problem I personally ran into and adding more calmag only made it worse. Most calmag are a 4:1 or 5:1 ratio of calcium to magnesium. If your base nutes already have a high ratio of calcium which they often do, this can cause some trouble.

Also, if you have harder water, you're probably already getting a lot of trace amounts in there too.

Strong lighting also allows you to run with more calmag as the plant will require more for chlorophyll.

So someone with 0EC water and high intensity LEDs could running 5-7ml magnesium no issue, but someone with hard water and lower powered lights might run into trouble.

I'd recommend, instead of upping your calmag. Dial it back to nothing and trust in GH bloom to supply the baseline magnesium as it should. Then make up a foliar spray of Epsom salt that you put on before lights out. Make sure to spray under the leaves. The ratio is around 3.5grams per gallon, but you can go up to 10-15g (a tablespoon) depending on how mature the plant is and how bad the deficiency is. Put the spray on once every 3-4 days.

I had this exact issue last grow and dropping the calmag and spraying with foliar had everything come right in 3 days.

I know it may sound a little counter intuitive dropping the calmag. But you're still going to get the magnesium required without the risk of cation blocking because of the excess calcium.

Overall, the calcium may not be the issue and increasing calmag may work. But I just wanted to outline other possible scenarios so you can make an informed decision.

[u/Accidental_Ballyhoo → u/Jolly_Yellow5354]

I appreciate your input and it has me thinking. For this grow I’m using distilled water, and dialed in 5.8ph. My light may be too intense. I’ll check PPFD when I get home.
I’ve used foliar spray with good effect on other grows. Thank you again!

[u/Jolly_Yellow5354 → u/Accidental_Ballyhoo]

Safe as. Let us know how it's looking in a week.

If you're using distilled water, with an intense light you're probably safe with upping the calmag without worrying about too much calcium blocking it

[u/Accidental_Ballyhoo → u/Jolly_Yellow5354]

Here’s hoping!

[u/mango_proof_ → u/Accidental_Ballyhoo]

It's simple though more light intensity, raise the feed ppm. But the new growth looks fine so it's not an issue. Most likely you feed too little calmag at the start and eventually it balanced out. Obviously you need more when you pot up into new coco etc

[u/mango_proof_ → u/Accidental_Ballyhoo]

And foliar feeding with actual food is counterproductive, you want to build a strong root system for that. You should only really be spraying things that are not great in feeds like kelp or whatever where the foliar vs adding to water is night and day

[u/mango_proof_ → u/Jolly_Yellow5354]

Tbh not of this matters if you are feeding the correct feed in coco. A and b plus calmag in ro or distilled. People over complicate things.

[u/Jolly_Yellow5354 → u/mango_proof_]

Fair enough, if you're running a standard drain-to-waste in pure RO, keeping it simple with A+B and calmag works fine most of the time.

​The point I was making is mostly for high-intensity LEDs and/or tap water where the plant burns through Mg. Most calmag bottles are 4:1 or 5:1 calcium to magnesium, so bumping calmag just dumps a ton of extra calcium into the mix, which can end up competing with the magnesium at the roots anyway.

​An Epsom foliar is just an easy way to get pure Mg straight to the leaves in a couple of days without messing with the root zone

Chur boss

[u/Motmotsnsurf]

Cal mag

[u/Accidental_Ballyhoo → u/Motmotsnsurf]

Thank you. I’m adding 3ml /gal and thinking maybe 5ml is better?

[u/Motmotsnsurf → u/Accidental_Ballyhoo]

How much were you adding to start with?

[u/Accidental_Ballyhoo → u/Motmotsnsurf]

Started with 2ml/gal then up to 3ml when I saw first signs. It’s been feeding on 3ml for 2 days. It still seems low right?

[u/Motmotsnsurf → u/Accidental_Ballyhoo]

Yeah. With GH trio I would be at 5 ml all the time. You could just up to 5 or blasting a little with 7 for a couple waterings but 5 should be good overall.

[u/Accidental_Ballyhoo → u/Motmotsnsurf]

Excellent. Many thanks!

[u/GreenBastard5280 → u/Accidental_Ballyhoo]

Ill 2nd 5ml all around.

Helps maintain any sort of imbalance in the coco, if i don't buffer or well enough I get the same symptoms but the cal-mag will eventually fix the issue from progressing.

[u/Accidental_Ballyhoo → u/GreenBastard5280]

I appreciate this. I’m planning to “flush” with correct mixture tonight and fill the bases too. Sound right?

[u/GreenBastard5280 → u/Accidental_Ballyhoo]

I don't personally use wicks but yes, feed with good runoff with more calmag should help.

[u/Motmotsnsurf → u/Accidental_Ballyhoo]

If you are doing a wicking system I would just stay the course and continue to feed from the bases with the additional cal mag. Only time I flush is when I let the coco dry too much and salts build up.