Coco grow in week 8 flower, root pH is bonkers

[roperman]

GH nutes, 5 gallon cloth pots, coco : perlite is 2:1, watering every other day with 1/3 strength nutes and calmag. Up to now, runoff has always been really close to nute pH. But now runoff is consistently around 6.4 or 6.5. For the last 4 days I've flushed daily with three gallons (sometimes six gallons) of plain water pH'ed to 5.5 and no matter what, the runoff is pH 6.4. The buds look good, but the lower leaves are now pretty yellow. 70% of the plant looks good, the rest looks sick.

So something is going on in the roots - should I be adding Hydroguard? Is it normal for the runnoff pH to go on the high side this stage in flower?

[Chefbjy]

Isn't that pretty much the threshold for coco? How many weeks left? If it's close leaves just may be dying or it may be time to flush. But idk what strain...pics?

[roperman]

The strain is Northern Lights, it has about 5 weeks left to go until harvest, so thinking this is a little too early for so many lower yellow leaves. I'll have to wait until tonight when the lights go on for some pics.

I agree, 6.4 is in the range for coco, but I'm concerned that 5.5 inflow isn't bringing it down, at all. If the root pH is off, it may explain all the yellow leaves - it can't get the nutes it needs if the pH is out of whack.

[Sheesh]

My two cents: don't worry too much about runoff ph in coco, especially if it's not drastically off. Keep your water / feed ph around 5.8 to 6.1 is most important. Are you giving her a full 5 ml per gallon of cal-mg? Nutrient lockout can occur late in the life cycle and the treatment is flush, which you've done. You may be just fine by sticking to your feeding routine and final flush when ready. Looking forward to a picture. GL.

[roperman]

I'm using calmag in every water / feed. I'll try upping the pH to 6.0 and I'll check what comes out. But if I'm putting in 5.5 and 6.5 comes out in the runoff, then I'm guessing that 6.0 going in will exit at 7.0. If it does come out at 7.0 I'm guessing there would be some sort of nutrient lockout going on due to high pH. I'll try it and post what happens tonight.

[roperman]

[DoctorJohnson]

GH nutes, 5 gallon cloth pots, coco : perlite is 2:1, watering every other day with 1/3 strength nutes and calmag. Up to now, runoff has always been really close to nute pH. But now runoff is consistently around 6.4 or 6.5. For the last 4 days I've flushed daily with three gallons (sometimes six gallons) of plain water pH'ed to 5.5 and no matter what, the runoff is pH 6.4. The buds look good, but the lower leaves are now pretty yellow. 70% of the plant looks good, the rest looks sick.

So something is going on in the roots - should I be adding Hydroguard? Is it normal for the runnoff pH to go on the high side this stage in flower?

Did you use brick coco? I have used two different brands of brick coco and both need TONS of washing. Mostly it was a PPH issue (NaCl contamination, I assume, but I don't know) but the pH was off too.

That said, I'm with Sheesh: don't worry about the runoff too much.

I like Hydroguard for hydro, but I really truly don't think you need it for coco. It's expensive and doesn't keep, so there's no reason to buy it if you don't need it.

Photos would help. If the lower leaves are getting yellow at 1/3 strength FloraSeries in the flowering stage, I'm pretty sure you've just cut back on N too much. Give them some extra Flora Gro or whatever to up the N. FloraMicro would work too.

[roperman]

The coco's been stable, pH wise, but maybe with age now, it's changing. I would be surprised that it would be a problem in flower, after all this time. This is what I bought, and I did rinse it in about 30 gallons before use, it says it comes double rinsed already: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I'll try upping the N a little. GWE says that N is detrimental in flower stage, but what the heck, it's worth a try. I'll bump up the Micro. What puzzles me is that I've got contradicting signs: lower leaves are yellowing and dying, yet I have yellow tips that indicate nute burn. I can't have too little and too much N at the same time. That's what makes me think this is a pH imbalance in the roots.

I forgot to mention that I started mixing molasses into the nutes about a week ago and that's about when the root pH starting going way high, but I'm not convinced it was the cause. I've since stopped adding it, but root pH is still way higher than I'm putting in.

[Sheesh]

One option is to remove those yellow leaves and monitor. You just did a good flush which can help refresh uptake this far into the grow. Those lower fan leaves aren't doing too much for the plant anyhow, IMO.

[Chefbjy]

I don't think any leaves should be removed untill you know for sure the problem isn't spreading. If you can pull them off easy then that's okay but if it hadn't stopped and you remove semi green leaves it will just pull from the leaves you think are healthy.

[OzBud]

last grow I had I worried about trying to keep the drain pH at about 6 when it kept trying to drop below 5.5 in flower.
For the last 6 months I've been growing strawberry plants commercially in coir grow bags and we test drain pH but we don't do anything if it's not the same as our pH going in. Currently feeding with an EC of 1.4 and pH of 5.8 going in. Our drain pH is coming out at about 4-4.5 at the moment and I don't need to try to get it back in line. EC on the other hand, if my drain EC goes above 1.8 then I need to reduce my EC going in to 1.0 until the drain EC gets back down to 1.4

[roperman]

Interesting that your runoff pH in flower was low and mine is high.

Since the root pH is seemingly out of whack, maybe your Great White mycorrhizae would help that.

[OzBud]

I run the flora series plus all additves/supplements at about 70-75% strength in coco except for CALMAG, I always use that at full strength

[roperman]

I use full strength calmag every feed and every watering, 1/2 teaspoon per gallon now in flower. Do you mean 75% of the 1/2 strength regimen that's on Nebula's coco chart for GH? If that's true, you are using about 3/8ths nute strength. Do you use this every time you water or do you feed, water, feed, water?

[OzBud]

no, 75% of the full strength mix from GH, so 50% stronger than nebula's. I water with all nutes every second day for the first week then daily until harvest

[roperman]

Good to know. You've got it down because I was at half strength and got either nute burn or some sort of deficiency.

[DoctorJohnson]

> The coco's been stable, pH wise, but maybe with age now, it's changing.
Nah, that doesn't make sense. It's just cellulose fiber (plus people use it over an over). It has to be something else.

> This is what I bought, and I did rinse it in about 30 gallons before use, it says it comes double rinsed already: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I have bought brick coco off Amazon a couple of times now. Both times it said ultra pure, triple washed etc etc, but when I put my PPM meter in it said otherwise. From now on I'm ponying up the $$ for name brand (GH!) washed, bagged, pre-Ca-treated coco. Spending hours washing the crap out of cheap coco is for da boids.

> I'll try upping the N a little. GWE says that N is detrimental in flower stage, but what the heck, it's worth a try. I'll bump up the Micro. What puzzles me is that I've got contradicting signs: lower leaves are yellowing and dying, yet I have yellow tips that indicate nute burn. I can't have too little and too much N at the same time. That's what makes me think this is a pH imbalance in the roots.

You can damage the tips with just one overfeeding that's used up by the plant or washed away by a flush or diluted by added water. My point is a toxic concentration and come and go in a matter of days.

> I forgot to mention that I started mixing molasses into the nutes about a week ago and that's about when the root pH starting going way high, but I'm not convinced it was the cause. I've since stopped adding it, but root pH is still way higher than I'm putting in.

I've tried molasses a couple of times and think it's better to put it on your oatmeal, but I don't think it does any harm, either. It won't affect pH.

I have to stay with my first guess that like so many of us, in flower you just got the N too low. It happens all the time.

Again, if you just water once a day (or 2X daily in my case) with diluted nutes--say 50% of Nebula's chart--you should't have any problems. (But as OzBud says, keep the Ca/Mg at 100%.)

<edit> I looked at your photos again. It's so hard to do diagnosis from photos, but you know what I'm starting to think now? Maybe (just maybe) magnesium deficiency: http://www.growweedeasy.com/magnesium-deficiency-cannabis When I skipped adding CaliMagic one time earlier in this grow (I was just topping off the reservoir and thought I could coast on last weeks dose), I got classic Mg deficiency symptoms of interveinal chlorosis. Mine looked more like Nebula's photos than yours, with greenish veins and yellowing in between, but your leaves look like they could be just more advanced. And as my doctor says, there's no reason that just because you have cancer you can't have a heart attack, which it to say it could very well be BOTH N and Mg deficiency--they're both very common.

In any case, bottom line, do make sure the 1) you're feeding enough, 2) your feeding regularly (daily is my preferred), and you're giving any coco grow plenty of CaMg, especially if you live somewhere with soft water).

And finally, you're in the home stretch and your flowers look good, so you're doing something right!

[roperman]

Since noting the runoff pH was way above normal, I have been flushing with 3 gallons plain pH'ed water followed by almost two gallons of nutes, at about 30% strength, every day. The yellowing leaves haven't spread too much and the leaves on the colas look good, green with no tip problems.

I've read up on Ca and Mg deficiencies and in mid veg I'm pretty sure I had issues. My cheapo pH meter went out of calibration and I was mixing up nutes that were between 5.3 and 5.8, when I thought I was making 5.7 to 6.2. The pH was much lower than I knew. I've read that Ca and Mg are best absorbed at pH levels higher than 6.2, so the plant's nute pH never got up there, I had deficiencies. I bought a better pH meter and have been really careful to calibrate more often now.

Nebula says if the runoff pH is above 6.5, to add nutes at 5.5, which is what I've been trying. Sheesh says to keep with the normal pH range and ignore the runoff. Maybe the 5.5 regimen has made it hard for the plant to get to the Ca and Mg. But if the runoff has been at 6.5, maybe it isn't a Ca or Mg issue.

My main question I guess was to find out if other's had the same issue with runoff pH in flower.

Thanks for the suggestions.