When to worry about yellowing? 5th week flower, rapid yellowing and purple stems, gg#4 auto.

Hey guys. Ive got a gorilla glue 4 auto here. Planted 1 March in potting mix (sphagnum peat, compost bark and perlite). I have experienced yellowing late in flower before, but this has happened very quickly.






I'm at week five of flower and assume to have around 4 to 5 weeks left. Does this look like something I should worry about? My medium pH is between 5.9 and 6.3 depending on where I test (hotspots). I water at 6.5 at 950ppm. Runoff in tray is usually 1000-1200ppm and pH 6.2. I use Canna terra Flores, Cannazym and pk13/14 together for 900ppm.

To cut it short, i would like opinions on whether this is a normal amount of yellowing for a plant with 4-5 weeks to go, or whether I should investigate further. My limited experience told me to check water pH/ppm, medium slurry ppm/pH and runoff tray ppm but it all came back relatively okay.

My gut instinct was telling me magnesium lockout from pH issues and a phosphorus deficiency (due to red fan leaf stems and purple streaking on main stems) but the pH seems to be okay and I'm giving a PK boost as of last week.

It's strange because the bottom leaves are falling off, but then there's this perfectly healthy area in the middle, then the tops are yellowing and the stems purpling.

Under a mars TS 600 (100w) and 6x e27 warm white led bulbs (23w each, 3000k/6500k/IR) for a total of 220w. Sits around 28c hottest and 18c night, at 40-55% humidity lately.

The pk boost,messes with everything.Quit using it, stick with basic food. your plant is low on N,the 13/14 has messed up the balance.

myke said:

The pk boost,messes with everything.Quit using it, stick with basic food. your plant is low on N,the 13/14 has messed up the balance.

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I'll give it a go. I only started pk last week, and used it on Tuesday after flushing and stabilising medium pH (was acidic at 5.2). Was planning again on Tuesday. I don't think one application would do this much, but I'll try mixing just base flower nutes to 900ish and see how we go.

The feed schedule for peat based potting mix recommends the use of pk around week 5 or 6 of flower for a week in total. I thought I'd try it as their description of potassium and phosphorus deficiency showed similar purple stems and petioles, red leaf tips and edges, chlorosis and brown/red spots.

My instinct is to just feed it straight flower nutes in pH 6.5 water and hope it hangs in there the next few weeks until harvest. Might try higher ppm, might not...I have plenty of shit I could try and remedy it with, and everyone I know is suggesting foliar spray every other day alongside supplemental shit left right and centre but I really couldn't and wouldn't 5 weeks into flower.

myke said:

The pk boost,messes with everything.Quit using it, stick with basic food. your plant is low on N,the 13/14 has messed up the balance.

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I keep telling people this. Keep it balanced through the whole run. The plant will take what it needs.

Your plant is nitrogen deficient, that is obvious. I don't think one dose of a PK booster would yellow it out that bad, but it definitely will speed up the process especially if it were already "in the making".

I bet your soil, or you, was not feeding enough nitrogen to meet the plants needs to begin with and the PK just sped it up. I personally would increase the nitrogen and feed half doses of the PK. Good luck.

psychadelibud said:

Your plant is nitrogen deficient, that is obvious. I don't think one dose of a PK booster would yellow it out that bad, but it definitely will speed up the process especially if it were already "in the making".

I bet your soil, or you, was not feeding enough nitrogen to meet the plants needs to begin with and the PK just sped it up. I personally would increase the nitrogen and feed half doses of the PK. Good luck.

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Cheers. I realised it was nitrogen deficient, but figured as I was using over the standard dosage of veg nutes until second week of flower, and recently switched to flower nutes at 7ml/L (2ml/l more than recommended) that I should be safe from nitrogen deficiency and looked at other avenues. A TDs meter soon made it obvious that with a 150% dosage of base nutes, the ppm was only 700.

I then looked at how much nitrogen the Canna terra soil that the nutes were made for contained, and it is far higher than the medium I am using. Assuming they were both sphagnum peat/compost mixes with added fertilizer, so should be similar in properties was my mistake.

VincenzioVonHook said:

I'll give it a go. I only started pk last week, and used it on Tuesday after flushing and stabilising medium pH (was acidic at 5.2). Was planning again on Tuesday. I don't think one application would do this much, but I'll try mixing just base flower nutes to 900ish and see how we go.

The feed schedule for peat based potting mix recommends the use of pk around week 5 or 6 of flower for a week in total. I thought I'd try it as their description of potassium and phosphorus deficiency showed similar purple stems and petioles, red leaf tips and edges, chlorosis and brown/red spots.

My instinct is to just feed it straight flower nutes in pH 6.5 water and hope it hangs in there the next few weeks until harvest. Might try higher ppm, might not...I have plenty of shit I could try and remedy it with, and everyone I know is suggesting foliar spray every other day alongside supplemental shit left right and centre but I really couldn't and wouldn't 5 weeks into flower.

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As suggested stop with the PK boost. What are you measuring soil pH with? The only tester that will accurately tell you is an expensive one. The cheap multi tester meters are nothing but trash and should be put there.

You flushed the plant so any nitrogen from your veg nutes were flushed out, most likely the start of your yellowing. You also stated you switched to "flower nutes" and fed them more then recommended, why? Even normal recommended amounts are usually too much. They also usually contain no nitrogen or very little.

Plants still need nitrogen in flower so cutting out all veg nutes isn't a good idea.

twentyeight.threefive said:

As suggested stop with the PK boost. What are you measuring soil pH with? The only tester that will accurately tell you is an expensive one. The cheap multi tester meters are nothing but trash and should be put there.

You flushed the plant so any nitrogen from your veg nutes were flushed out, most likely the start of your yellowing. You also stated you switched to "flower nutes" and fed them more then recommended, why? Even normal recommended amounts are usually too much. They also usually contain no nitrogen or very little.

Plants still need nitrogen in flower so cutting out all veg nutes isn't a good idea.

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If I used their recommended dose of flower nutes, it was only coming out 600-700ppm. They expect you to use rhizo, zym, Flores, boost and PK lol to get 1000-1200ppm, so I childishly thought I could just up the base nutes to 900-1000ppm and go from there. I have been told 500-700 for veg and 900-1000 ppm for flowering and didn't want to add everything in their feed line to get there.

Only flushed as my medium pH was low (around 5 flat due to peat medium). Measuring PH with a bluelab EC/TDS pen, a bluelab pH pen (around $100 each) and a set of cheap $30 pens as a backup. The soil pH metre is a groline digital, so all legit stuff.

I flushed with pH 7.0 water due to low medium pH, at 900ppm of base nutes with a bit of added dolomite, so it wasn't a straight water flush, so it shouldn't have flushed out nutes, just the salt buildup at the bottom.

Before flushing my runoff in the tray was at 1600ppm, and pH 5.5. After it was 1000ppm and pH 6.5 so I thought I did alright. Runoff is still around 900-1100ppm now, and 6.5.

By the way, the flower nutes do contain nitrogen. The veg nutes were 3:1:4 and the flower nutes are 2:2:4, and there was never a time I flushed with plain water, just pH upped standard nute formula at 900ppm until the runoff pH and ppm was even with the formula going into the medium.

To sum it up, I was using Vega and zym at 700ppm during veg wk 2-5, and 900ppm of Flores from week 6-now. Added PK last week at 75% dose last week, total of 970ppm. I was under the impression that using ppm and ex was more important than using their recommended dosage, but I was probably dead wrong.

Keep in mind I have no idea what I'm doing lol. I'm used to growing outdoors in good soil. My last photos outdoors never dealt with yellowing until the last week or two, and it was always the lower leaves. Its the first time I've had a nitrogen deficiency that hits the top first, and only hits a few lower leaves.

I was under the impression that using ppm was the safer way to measure nutrient strength, but I'm probably crazy running it at 150% to get the required ppm.

I'm just not sure if I should worry too much about supplemental nitrogen now or just keep feeding flores at 2:2:4/900-1000ppm. The only type of supps I have with nitrogen are blood/bone meal, Pro Cal 2-0-0 and a 5-2-2 topsoil amendment powder.

Ok you are at start of week 10 tomorrow. It's an auto. You have done well.

While it might run 6 more weeks, as an auto my guess is 4 weeks max.

It's true it is starting to show N loss but at this stage that's not so bad. It's normal really, although you can feed them to stay fully green.

Healthy is most important now. I would not chase the N that is being used up. Feed flower nutes only as needed, and dont base that on the ppm of runoff, base it on how it looks.

Dont stress about yellow leaves in the last weeks of an auto.

You could water only all the way to the finish and have a nice harvest. That should give you some perspective on how hard to chase the yellowing.

ComfortCreator said:

Ok you are at start of week 10 tomorrow. It's an auto. You have done well.

While it might run 6 more weeks, as an auto my guess is 4 weeks max.

It's true it is starting to show N loss but at this stage that's not so bad. It's normal really, although you can feed them to stay fully green.

Healthy is most important now. I would not chase the N that is being used up. Feed flower nutes only as needed, and dont base that on the ppm of runoff, base it on how it looks.

Dont stress about yellow leaves in the last weeks of an auto.

You could water only all the way to the finish and have a nice harvest. That should give you some perspective on how hard to chase the yellowing.

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Cheers. I figured I'm just being a bit pedantic, and probably putting too much stock into the numbers instead of the actual plants body language. Was mainly freaking out as it happened so quickly, and predominantly the top of the plant. It doesn't help that some of regular growers here just have extremely nice plants as a comparison haha.

Some of the Redding on the top leaves actually looks really cool at the moment.

Excuse the light spectrum. Don't have the battery for flash ATM so left the light on lol. The first plant I've had that has had red discolouration on the top sugar leaves like this.

ComfortCreator said:

Ok you are at start of week 10 tomorrow. It's an auto. You have done well.

While it might run 6 more weeks, as an auto my guess is 4 weeks max.

It's true it is starting to show N loss but at this stage that's not so bad. It's normal really, although you can feed them to stay fully green.

Healthy is most important now. I would not chase the N that is being used up. Feed flower nutes only as needed, and dont base that on the ppm of runoff, base it on how it looks.

Dont stress about yellow leaves in the last weeks of an auto.

You could water only all the way to the finish and have a nice harvest. That should give you some perspective on how hard to chase the yellowing.

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You keep bringing up the fact that it's an auto. What does that have to do with anything?

I'd worry about any plant that was yellowing that much and that early in flower. It is FAR from normal.

twentyeight.threefive said:

You keep bringing up the fact that it's an auto. What does that have to do with anything?

I'd worry about any plant that was yellowing that much and that early in flower. It is FAR from normal.

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I bring it up because autos finish a lot faster than photos. The light cycle is not 12 12 as you know.

Do you really have enough experience to say that where he is at is far from normal?

ComfortCreator said:

I bring it up because autos finish a lot faster than photos. The light cycle is not 12 12 as you know.

Do you really have enough experience to say that where he is at is far from normal?

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Any cannabis plant yellowing at that point in flower is abnormal, yes.

Limited experience overall but I must have the worst luck in the world as I've never had a fast finishing autoflower. Quickest I've had one finish was 93 days seed to harvest.

twentyeight.threefive said:

Any cannabis plant yellowing at that point in flower is abnormal, yes.

Limited experience overall but I must have the worst luck in the world as I've never had a fast finishing autoflower. Quickest I've had one finish was 93 days seed to harvest.

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That's what I'm saying. I have 10 running right now. All will be done before 93 days. And fully finished. Dont be 100% sure you got it all down! I dont, but I've run lots of plants now and know where he is at is no issue to worry about (imo).

ComfortCreator said:

That's what I'm saying. I have 10 running right now. All will be done before 93 days. And fully finished. Dont be 100% sure you got it all down! I dont, but I've run lots of plants now and know where he is at is no issue to worry about (imo).

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So wait. Because my autos take longer to finish that means I don't have my growing down? What issues am I having other than longer finish times? I don't grow stick figure autos.

Lol dude chill.

I'm saying your opinion that the yellowing is a big issue is off base where he is at. The purpling is just fine too. It could be better, but it's a lot closer to perfect than sxxx.

ComfortCreator said:

Lol dude chill.

I'm saying your opinion that the yellowing is a big issue is off base where he is at. The purpling is just fine too. It could be better, but it's a lot closer to perfect than sxxx.

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Chill? I'm not upset?

His plants are showing a deficiency early in flower. It is an issue and if not corrected it will continue to get worse. That was my only point not that his plants look like shit. They look great other than the issues he's having. Deficiencies are not normal, period.

You straight out discounted my opinion based on the fact that the autos I've grown have taken longer than yours. The 93 day plant was actually done in 90 my mistake. Started flower in 30 days and finished flowering in 60.

If your plants are finishing quicker than that they are either tiny little sticks that start flowering in two weeks or you are chopping them early.

Update. Still obviously locked out, but I've added dolomite twice over the last month, I've tried higher pH (7) watering for a few days, but the medium keeps going straight back to 5 when it dries out some. No change in feeding (950ppm, Flores and zym). Looked into the medium and it's just an acidic medium being peat moss based and normally used for azaleas, Gardenia, berries and similar. At least the new growth is darker now. First indoor grow so I'm just Gunna coast to harvest and try not to fuck with too much.




I've got a GDP auto, a Blackberry Gum auto and an AK420 auto all ready (have tails) to pop in some pre buffered (6 flat) Coco/perlite mix tonight, and a bunch of jacks cleaner#2/purgatory photo seeds here I'll try in a few weeks once I'm done lining my closet with mylar and routing the filters and fans in the roof.

cheers for all the help guys. I'm sure going Coco over peat will negate some of my lockout issues due to low pH. Here's hoping the next 3 weeks will treat her kindly.

Ph in flower seems ok 6.4 is what lve read as sweet spot, l feed 5.4 every week or so, pk half or quarter strength at onset of 12x12, then again week 3. Yellow week 5 not often but some strains. Nitrogen is important all through grow , my veg nutes are 4x4x4 flower is 8x6x11 which is 2x the Nitrogen. As Therion said BALANCE. is good. Yellowing top and bottom, no clue. Sounds like more than one problem. Good luck and these riu guys and girls are worth more than all the books and youtube videos x10. Gg is known strain to carry tobacco mosaic viris. Sooo? Never seen it but gg4 last year, clone did great mom went wierd during onset of flower. Never got to see either finish unfortunately. Ps. Very pretty bud, looks nice.