Rust Spots mid-flower

[Mañ'O'Green]

Hey thanks for welcoming me! I think one of my problems has definitely been that I’m getting a lot of conflicting info from various sources, so it’s hard to figure out what’s what (and as a noobie I haven’t a clue myself). For instance, when I flushed a couple weeks ago I did so because I was having issues with a different plant and it was suggested that I was crazy for having not flushed yet with fox farm nutes. So I flushed and now I’m having these new problems. ‍♂

You fine folks here seem to know your stuff, so I’ll go straight water for a bit and see how we’re doing

I have been growing something for over 50 years and Cannabis indoors for over 7 years in this latest stretch and I still have problems and learn new stuff every day.

I consider flushing as a last ditch effort to save a plant that is dying. The reason is the root biome. roots even in hydroponics creates a biome of living microbes around them. Organic Living Soil is the epitome of this biome. The microbes make nutrients available to the plant. The microbes are developed in the early stages of root growth and are not easily replaced after being flushed away. They are never likely to be the same after a flush. Mykos and other products like Recharge can be helpful but you need to be careful adding them because they can increase the nutrients available to the plant at a time when the plant may not need what they enhance?

Yes there is so much conflicting information on the web. The ONE that causes the most problems is the idea of needing extra Cal_mag. For the most part soil growers should never need extra there is plenty in all cannabis oriented fertilizers and organic soils.

If you grow hydro in Coco you do need extra especially if you run RO water but that is just about the only time. I have run across 2 growers here in the last few years who's tap water was so soft they needed a little but that is rare.

Anyhow it is a learning adventure we are on.

 

[low_and_slow]

And ultimately, you think you figure it out and then try new genetics that want something else entirely.

It's life.

 

[pg2052]

Hey all - so I just watered my plant. The 3 gallon smart pot took about 4/5 gallon of tap water. I let my tap water sit out for about 48 hours in a big 5 gallon jug before feeding plants with it -- someone told me at some point that I should do that so that some of the chlorine would evaporate (if someone thinks this is a wasted endeavor, please let me know). I feed/water to runoff of about 20% -- something that was suggested to me as a user of Fox Farm liquid nutes, in an effort to prevent salts from building up (again, if you all think I should be watering differently, please let me know).

Anyway, the water was pH'd down to 6.3, and had 135 PPMs; the runoff had a pH of 6.6 and 400 PPMs. I also did a slurry test -- took one sample from the outer edge of the pot, just slightly below surface: 6.7 pH and 78 PPMs; and one sample from right next to the main stalk: 6.9 pH and 55 PPMs. @Mañ'O'Green @Proph @low_and_slow -- any additional thoughts based on those readings?

Thank you everyone - I really do appreciate you all lending a hand.

 

[pg2052]

Also, is there any decent autoflower literature out there? Or even just a general indoor growing book that would be a good place for a new grower to start? I'd really like to get a handle on some of these big picture concepts. Or should I just hang around this board and learn as I grow?

 

[low_and_slow]

Jeff Lowenfels wrote a book about autoflowers recently worth checking out

 

[pg2052]

Hey @Mañ'O'Green @Proph @low_and_slow -- so I waited 48 hours and watered again (plant gets pretty light after just 36 hrs or so). I pH'd my tap water to 6.5, and poured about a gallon of 145 PPM. Pretty substantial runoff -- mostly clear. Runoff water tested at 6.5 pH and 355 PPM. Stick with pH'd water only for a while? Rusted/crispy leaves continue to grow in at the top of the canopy. Eased the light back to around 35 DLI, in case I was burning them a bit. TIA!!

 

[Proph]

I would start back feeding in the 4-500 ppm/ec range and watch how the plant reacts. You want to be watching the healthy leaves to make sure the issue isn't speeding.. The damages leaves won't recover, so watch and protect the healthy ones that are left.

 

[pg2052]

I would start back feeding in the 4-500 ppm/ec range and watch how the plant reacts. You want to be watching the healthy leaves to make sure the issue isn't speeding.. The damages leaves won't recover, so watch and protect the healthy ones that are left.

Great, that's what I'll do. Thanks for the time -- you guys have been super helpful!

 

[Mañ'O'Green]

@pg2052

If you think the pot is getting too light water/fertigate more often. When the pot weighs light at ~50% of the water weight it is time to water/fertigate again.

 

[low_and_slow]

I'm maybe a bit confused with what's going on, so I'm going to run through my diagnostic checklist just to share my observations:

1) This is related to an immobile nutrient because it appears on new growth, not on the lowers and spreading to the uppers.
2) This appears to be related to Calcium based on the appearance of rust spots on the leaves and a 'burned' appearance.
3) The plant does not have a Nitrogen deficiency; the plant is showing signs of potential N-tox.
4) pH seems to be stable around 6.3-6.5, both in terms of feed and runoff (can you confirm your instrument is calibrated and/or do another test with drops to verify the color is close to this range through non-electronic means?)
5) There is visible cupping along the leaf margins, indicative of potential heat-stress (DLI measurements rule-out light stress)
6) Runoff EC does not indicate an obvious accumulation of salts in the medium (again, can you confirm calibration of your instrument?)

Possible issues:
Ca lockout due to high pH or N/Mg toxicity?
Heat stress?
Stress due to extremely high VPD (i.e. low RH)?