late flower nutrient question

KT cockroach

New Member
Hi all. Fresh meat here.

This is my first grow. It's just in a closet, 150W HPS light with a not-so-great exhaust system I hobbled together with a USB fan. There's a standing fan as well and I leave the door cracked open during the day so there is more air circulation. However if I do leave the door closed all day if I'm at work or travelling it gets noticeably stressed so I know the circulation could be better. The grow medium is Pro-Mix Potting Mix amended with some organic Sea Soil compost. 21 quart pot so roughly 5 gallons. I've been mainly watering with tap water which is a little alkaline (pH 7.8 or so), but have been flushing with rain water (pH 7.2) and distilled water due to some nutrient burn which I will get back to in a second.

The plant has been pretty healthy for the most part. It is from bag seed so I don't know the strain but it behaves like a sativa or probably a sativa-dominant hybrid. I did not feed it at all during veg, and now that I've done more reading I think that it probably had a bit of N toxicity during veg (there was some clawing in the shaded areas) but since I wasn't feeding it at all I just left it alone and didn't think about it.

I didn't know about "the stretch" yet and about 3 weeks into flower I had a poorly timed trip out of town. When I got back the plant had grown about 2 feet and had pretty bad heat stress. By now it was into the 4th week of flowering. The tips of many of the leaves were yellowed and a bit curled which I attributed to the heat. I treated it and it recovered but there are a couple of very long internodes which isn't ideal. Lesson learned. This is also when I noticed yellowing lower leaves and figured out that it had an N deficiency (which makes sense since it hadn't been fed at all and had just doubled its size). So I started feeding it bloom nutes (DynaGrow 3-8-8 ) at about .75mL/L which slowed down the yellowing. After about 5 days some more yellow was creeping in so I fed it a little more enthusiastically... which was a big mistake! I started to notice more aggressive symptoms of nutrient burn. The leaf tips were already a bit curled and burnt from when I went away but it spread, and instead of the leaves turning all yellow and then dying they were just partly turning brown and crispy while the rest of the leaf was still green. This was about a week ago and since then I've been flushing with a mix of rain water and distilled water. I checked the pH of the run-off to rule out pH problems and it tested at 6.8 or so. Here are some photos I took today of the affected lower leaves: DSC_0191.JPG DSC_0193.JPG DSC_0195.JPG

Since then the plant has recovered somewhat. Some of the claw leaves are unclawing but most of the newer leaves near the colas are still a very deep green from nitrogen toxicity. (See here: DSC_0190.JPG ). However there are some new symptoms like a bit of mottling on fan leaves near the top of the plant (See here, there are some darker spots beside the yellowing margins. you might not even be able to see them they're so tiny: DSC_0189.JPG ), and the lower leaves are still turning brown and crispy and dying. That being said the buds are still fattening up and any damage to the plant seems to be minimal.

My very long-winded question is this:
Do I need to worry about nutrient deficiency symptoms this late into flower or can I just keep flushing the soil until harvest? The mottling might indicate a deficiency but again it's super mild and almost unnoticeable. The browning leaves near the bottom I think are just toast from nute burn but it might be a deficiency as well I suppose. Again, this is the 8th week of flowering, so harvest quite possibly could be around the corner, but the strain is an unknown sativa so it could be a few weeks still. Some of the pistils have changed colour and the trichs have started to get milky but most are still clear.

Here are some more photos... Not as fat as a lot of the beauties on these boards but I'm only using 150W so I don't think it's that bad... Let me know if you think otherwise :)
day49.jpg DSC_0197.JPG

I appreciate your thoughts! Cheers!
 

NewtoMJ

Well-Known Member
Alright my man, I read your post. And from what I can see you're not too bad. After all this flushing I would try to feed with something light, because you definitely have a few more weeks but you don't want to overload her again.
 

KT cockroach

New Member
Alright my man, I read your post. And from what I can see you're not too bad. After all this flushing I would try to feed with something light, because you definitely have a few more weeks but you don't want to overload her again.
Awesome! Thanks for your help!
 

Alienwidow

Well-Known Member
I agree with the last poster. Feed light and ride it out. The plant actually looks like a nice plant. Sativa traits for sure and i wouldnt be surprised if the smoke is really good. Also if your using soiless, you might want to get some calmag for the next grow.
 

KT cockroach

New Member
I agree with the last poster. Feed light and ride it out. The plant actually looks like a nice plant. Sativa traits for sure and i wouldnt be surprised if the smoke is really good. Also if your using soiless, you might want to get some calmag for the next grow.
Cool! Thanks a lot! I am using soil but I'll keep that in mind if I change it up in the future.
 

Alienwidow

Well-Known Member
Cool! Thanks a lot! I am using soil but I'll keep that in mind if I change it up in the future.
Pro mix is soiless. Its made from peat, which contains no real organic potting soil. The peat has no food for the plant held within itself, like an organic potting soil would. Thats why constant feeding and micro nutrient supplementation is necessary, and cal and mag are two very important micros.
 

KT cockroach

New Member
Pro mix is soiless. Its made from peat, which contains no real organic potting soil. The peat has no food for the plant held within itself, like an organic potting soil would. Thats why constant feeding and micro nutrient supplementation is necessary, and cal and mag are two very important micros.
Ahh! Ok that makes sense. Cheers
 
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