Hey folks!
was hoping for some guidance regarding my plants. A couple of the larger ones have started developing these brown spots on the older leaves. No bugs underneath. There are however some bugs in my space because I’m using a biologically rich soil (have lost some seedlings actually from chomping, but that’s part of the price I’m paying for learning)
anyway, I’m not inclined to think it’s bug related because it’s on older leaves but I could be wrong. I do sometimes spray water on them when lights are on but is that really harmful or bro science?
my buddies tell me they’d just cut off the brown part but I don’t like the idea of cutting the plant yet when it’s still this young. And without knowing what happened.
Anyway thanks!!
This is almost certainly due to lack of Calcium uptake. But hold on --don't assume that means you don't have enough calcium and that you need to go adding Cal-Mag. The clear indicators are that you have browned spots with necrosis that are not only at the leaf edges AND you have distortion/twisting of the leaves which is a clear telltale sign that Ca is not being taken up. The problem is that there can be several reasons for the plant not getting enough calcium, from not enough in the soil, to pH lockout, to lockout due to excess Mg, to the soil being too dry, to the soil being too wet.
I have a strong hunch your soil is too wet. I say this because you mentioned having rich soil and spraying water and it sounds like you may have fungus gnats, too because they love soil that is too wet. What is your watering practice and how do you know when to water? A simple soil moisture meter can be huge help, and they cost only about $10-12 bucks. alternatively, you can simply stick you finger in the soil 1-knuckle deep, half way between the stem and rim of pot. It should be just slightly moist, not wet. Over-watering promotes anaerobic environment, shifts your pH, promotes pathogens, and kills root hairs. Sometimes less is more.
If my hunch is correct, you need to dry out the spoil, which is more difficult in a plastic pot. Make sure your pots drain well and they are not sitting in runoff. Place a small fan on the soil on low (like USB sized), and reduce your RH to promote plant uptake of water. No wait -- scratch that. I see your RH is already pretty darn low. If you can turn up your light a little, or drop it lower a few inches, do that too. The damaged tissue will not grow back. Do not cut out the damaged area else you risk infection. Leave the leaf there because the parts with chlorophyll will keep making energy for the plant.
Yes, spraying your plants when they are under bright light can cause lots of burned spots from the drops acting like lenses, but it does not look like this, and that does not cause leaf distortion, but lack of Ca does.
@im_sparky I’m so glad I asked this and you responded. I had that feeling as well, about overwatering. The calcium component though is really interesting. So the soil I'm using is a compost I’ve made which I believe should be pretty abundant in macros and micros. As well as blood and bone meal, and 2-8 mm clay aggregates. I added these to test and see whether I can continue using these pots for many cycles, assuming I keep enough biology in there that the clay will give off some minerals, and I will just have to add macros (is the thought). I was aware going into it that drainage was going to be curious. I do have a moisture meter I use, some of them are in the green some of them are way too wet. But that’s at like 2-3 inches- I let the top 1”-2” dry out. However I think that I can and should let it get even a bit drier than that.
As for the lights, the plants are growing but slowly. I’ve attributed that to the temp (high 50’s low 60’s). But the lights are running at 50% (per Vivosuns germination/seedling guide). Plants are at different heights but it’s in the range of 20”-28”. What’s been your experience with that? I set it up so that I have plenty of room on my light cables to go up or down. Or, I can increase to 75%.
But yeah regardless of light I will let those guys dry out. Thanks Sparky, seriously 🙏🏼
@soiledseed When you say you have added clay aggregates, do you mean something like hydroton?
I am wondering about your soil and aeration, which is a possible reason you could have a Ca issue. If there is not enough air, either from too much water or too dense of a substrate, then that can also cause a Ca issue along with pH and anaerobic conditions. I am wondering what percentage of aeration material you have? Generally speaking, here is basic mix for a good soil, assuming the compost is filled with balanced nutrition and beneficials.
A Basic Cornell-like mix:
1/3 compost
1/3 peat/coir
1/3 aeration, such as perlite, vermiculite, pummice, lava rocks (each one behaves differently)
+ mineral and additional nutritional content: meals, rock-dust, sand/silt/and traces of clay
As for plant height, yes you are going to get variations due to the varied genetics in seeds and strains. Even with clones you will see some variability, especially in soil, due to differences in soil.
@im_sparky okay, right. Per the clay aggregate, no I’m not using the heated/puffed up clay balls. These are from dried clay soils which I sieved between 2-8 mm. I’m studying soil science so wanted to experiment with something I thought made sense, that could rival or surpass the Cornell standard mix.
The main idea is A)local materials, super sustainable B)naturally biologically active C) not wasting space in the pot
My thinking is that putting inert drainage materials into the pot is wasted potential root space. The compost has a good amount of woody twigs/leave and detritus that gives it some “structure” and the clay aggregate as mentioned earlier would feed the soil over time with minerals. Plus add another dimension to the soil potentially in structure. If it was clay powder/loose it would probably hinder the composts ability to drain.
so that’s the soil, but again haven’t had it tested so I’m assuming Calcium is good. If I keep seeing the twisted leaves, and am managing the water properly, would you advice making a calcium solution with eggshells and feeding?
here’s a current picture of that plant, whole plant is dropping. Moisture is kinda low. I think it’s now too dry. I am seeing roots out the bottom so maybe I should pot up. Let me know your thoughts.
And thanks for taking your time! I appreciate it 
@Juglans thanks man! Things seem to be going okay overall- I’m just trying to fine tune. So lucky that there are people here with a lot of knowledge in things I don’t have 😁
@soiledseed With your own mix, it is hard to say because it is not clear if you have enough calcium in there. What calcium component did you include? Did you have your compost tested? She definitely is looking dry to me know. Keep in mind any nutritional issues you are seeing now are from about 10-14 days prior. Not knowing what is already there is the difficulty.
I don't see any continued spotting or leaf distortion in the photo. If you don't see any additional symptoms after you let her dry out a bit, then you are likely fine. Cannabis can take a lot of calcium and store it without issue, as long as you do not overdo it with Mg. If you have some WCA then I don't think a small dose would hurt.
If you are taking an agronomy class, then you likely know, but I'll throw this out there just in case. It would be better to keep that soil evenly moist (if you have enough aeration) rather that have it swing between too wet, to too dry.
@im_sparky Thank you so much man!!
Your insights are super- well insightful. Helpful. I appreciate your time and knowledge.
As others have said the plants needed some time to get acclimated, but I think more than that I’ve basically stopped watering, and repotted into larger containers. Everything is looking great at the moment! Also I’ve been spraying the leaves (during light cycle, no apparent leaf damage yet) and throwing the humidifier on. And it’s getting a hair warmer, today was about 67F in the tent. So who can say exactly there are a few factors happening. But the soil drying I think is a biggie. Anyway, here’s some updated pics!
@soiledseed Glad to help, mate. There are a lot of great people around here helping out, and I'm just paying it forward.
I dont see anything to worry about. Its small plant adjusting to its soil.
If there's any drops of water on the leaves when the lights on it can burn the leaf and leaves a brown crispy patch, a bit like holding a magnifying glass in the sun. That's what it looked like to me but I could be wrong.
If the roots are just starting to reach the bottom of the pot then I would probably leave her in the pot for a wee bit yet to make sure they fill out to the sides of the pot too, that how I do it but that's not saying it's the right way.lol
But I dont think there's much wrong with her that I can see 🙂
Water till runoff and let it suck the water back in from the tray. Cannabis is not a cactus. Ur soil dosent look like clay. U cant over water in those.
Hey guys!
Thank you all for your inputs and insights.
I will post some update pictures, most plants are looking good! But I do have a couple of questions. I will post the 2 plants I have questions on.
1. This yellowing at the bottom. Am I to assume it’s a N deficiency? I should have enough in there. It is sharing the pot with a tomato plant that came out of the compost so I’m wondering if they are competing.
2. What is up with these leaves? The whole plant just looks bizarre. Is there something wrong? Or is it just a weird pheno? Supposedly an Afghani, which of the 3 in my tent, they’re all quite different morphologically.
also, the yellowing at the tips, I read that’s likely lightburn. Is that what others here have found as well?
Thanks!
On to the pics
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