Sick plant diagnosis

[Nate]

I thought maybe this would be a good place for people to post their questions about their sick plants. As a relatively new grower, I find it’s sometimes hard to differentiate between different deficiencies/excesses or other ailments.

[Cannabliss]

To help set this off here is a snapshot quick guide to visible deficiencies. 

[Nate]

I’m having a hard time posting this for whatever reason. I’ve typed it out 3 times now, and it hasn’t gone through once yet, which is frustrating. hopefully it doesn’t post it a million times later on..

 

I’ve been having some yellowing of the newest leaves on some 15 day old seedlings. The got a bit stunted due to a power outage last week from hurricane Fiona, and the the yellowing started after transplanting them to a coco/perlite mix. Initially I thought it was a calmag deficiency, so I started a twice daily foliar calmag spray a couple days ago. It didn’t seem to improve right away, so I checked my runoff EC, and it was around 1100 µS, so I fed/flushed with some nutrient solution ~500 µS last night. That seems to have worked, as it seems like the new growth is coming in quicker, but we’ll have to wait and see. I’m going to try to post this without the pictures, because I’m thinking that may be screwing up the post(?). I don’t know, I’ll try to upload the photos if I can.

[Keith]

This is a good one too.

[Keith]

And this has helped me a few times.

https://www.alchimiaweb.com/blogen/deficiencies-excesses-cannabis/

[Nate]

 

[Somatek]

What was the EC of the water/ferts when you watered them last that caused the run off to be so high?  Is  the coco/perlite mix fortified or a soilless mix that’s inert with no significant nutrients?  Were they drying out before getting transplanted as hydration affects the availability of nutrients in the rhizospehere (aka root zone), so something as simple as being late on transplanting and letting them dry out a bit too much between waterings can express as a deficiency when the issue is actually unrelated.  Diagnosing problems is hard as you need a holistic approach that considers how interdependent everything is in a grow, which is much harder then just looking at nutrients issue charts and trying to match a leaf to solve the problem.

[Nate]

I think I may have increased the EC prematurely as the yellowing was presenting. The coco isn’t fortified in any way, and they weren’t ever allowed to fully dry out, although I may have under watered them in the jiffy pucks, as I’ve never used them before and I wasn’t sure if I should water as much as if they were in coco etc. They definitely stretched a fair bit while the power was out, and were probably about a day late being transplanted because I didn’t want to stress them out any more than I had to. They seem to be bouncing back though, so I’m just going to keep things stable as far as nutrients/environment, and just wait and see.

[Nate]

 

[Somatek]

A high EC, especially if it’s N heavy, won’t express as yellowing leaves but the opposite with deep green leaves, curled leaf margins and bright green new growth.  I wouldn’t expect to see nutrient lock out in only 15 days unless you’ve been blasting them with nutes right off the bat.  It’s possible it’s completely unrelated to the nutes and was simply a result of being in the dark after Fiona.  It’s always good to keep in mind with soil that it takes a bit for the plants to show the effects of what’s changed, they aren’t overly reactive like we are.  Which is hard as we all tend to pamper our wee ones and fuss over them like mother hens.

With that said I wouldn’t be running my EC higher then 0.5 (or 500 millisiemiens but I’m just not use to seeing it that way lol) for seedlings anyway so everything you’ve done makes sense, flush the soil to get the EC into a range it should be at and give them time to show you how they react.

This is also why I take detailed notes when I’m using a new system or ferts, it’s much easier to learn if you have detailed notes of exactly what you did and when along with pics.  Especially for dialing in optimal feeding levels for a clone, if you have data you can look back over a couple crops and notice patterns like yellowing lower leaves at week X, which lets you know the plant needs the N cranked up a week or two earlier.

Glad you and the babies weathered the storm as well as can be expected and hope you all get some rest and recovery.

[Nate]

That makes sense. Could very well be due to the outage, I just wanted to get things within a better range for the stage that they are at. I kind of slacked with the notes this time around, last run I had been checking and recording runoff every feed. I’ll definitely have to keep better track from now on.

[NeuroticTurtle]

if weak nutrient solution worked, it sounds almost like you needed nitrogen N27 foliar feed instead of calmag.  From what I’ve been reading seedlings need an intense amount of nitrogen…

[Nate]

You might be right. I just figured if it was nitrogen, it would’ve started with the lower leaves since nitrogen’s a mobile nutrient. It may have just been the fact that they’re only on their first sets of leaves that threw me off. I was thinking they’d be getting some nitrogen from the calmag foliar spray since it’s a 3-0-0, but it may be that the pH of the foliar spray was out of range for the nitrogen to be available (I had it above 6.2 pH as per the tutorial on coco for cannabis).

[Cannabliss]

Was the coco precharged with calmag? I’m not a coco grower so I definitely have no authority in these parts lol but I have been reading up & eating a lot of stuff on it. Coco usually needs to be rinsed out & soaked in 150% strength calmag. (Unless it’s pre-charged)

[Cannabliss]

@nate I have now read through the above conversation. Not letting them dry out is the right path, as I hear coco shouldn’t be drying out between watering & feeds like soil. The issue must be in the medium. Have you tried 5.8ph?
The magnesium is looking like what it wants.
I didn’t notice this mentioned.. but could be the light be too close at too high of a setting?
I run a 150w light about 2ft away on 25-35%. 

[Nate]

Yeah the coco was pre rinsed and buffered, and I haven’t let the coco dry out. My input pH of my nute mix has been between 5.7 and 6.2. Also, I used the same coco coir for my last run (I’m using the unused portion of the bag I bought last time, not reusing the same medium), and I didn’t have any calmag issues that time. The light may be a bit too intense though, it is a 600w MH at about 2 feet away.

[Nate]

[Nate]

The seedlings seem to be bouncing back now, definitely seeing more vigorous growth, and a darkening of the leaves compared to the previous week. I’m going to continue on feeding at around 500 μS EC, and most likely continue with the foliar calmag as well, at least until I see some darker new growth come in. I’m definitely going to keep a close eye on them for the next few weeks, but it seems that they are improving.

[Somatek]

I kept my 600w mH a lot closer then 2ft with seedlings/freshly rooted clones, I’d be surprised if that’s the issue.  If you’re continuing to see improvement, considering the time frame it reinforces my belief that it’s probably stress from the power being out.  Especially as you mentioned they stretched during that period as etoliation is a reaction to stress.

[Nate]

Good to know. I didn’t think it was too close as I’ve had seedlings the same distance in the past, but I know I’ve seen some people say that you shouldn’t have them under intense light right away.

[Somatek]

People say a lot of things without necessarily knowing what they’re talking about, which is why I try and always be clear if I’m speaking from anecdotal experience or established horticultural facts based on peer reviewed studies.  Sadly there are many that are pot specific yet (compared to most crops at least) but that makes it all the more exciting when we do find some.

[Nate]

For sure. Personally I’d love to know the science behind things, but I definitely don’t want to discount the tried and true methods just because it isn’t proven in a study yet. There’s definitely a lot of bro science out there though, so I try to take everything with a grain of salt.

[Somatek]

The Handbook of Cannabis Production in Controlled Environments by Youbin Zheng is a wonderful book focused on factual, science based info from a list of contributors who’s credentials are intimidating.  Well worth the read if you want to deepen your knowledge.

[Nate]

Right on, I’ll have to check that one out.

[Author]

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