Black spots - Leaves curling down and drying up - Please help

[richrich]

Hi there,

I am first time grower. Have some plants growing outside in shade (to save plants from direct heat as temperatures here can go as high as 38 degree C).

I water them every few days when the upper soil starts drying up.

Recently the weather became very hot so I moved these plants inside in around 24 degree C and I topped them to stop the vertical growth anymore.

After a couple of days, I started to notice that the new leaves are getting black spots on them. I waited for a day or two but couldn't figure out whats the problem and they started to turn really bad now in like 4-5 days.

Please check the pictures below and suggest what should I do.

 

[MrRudeSnowman]

There is some temperature stress but plants don't look too good even without it. First of all you need to know what is your PH levels in water. When that's done you probably need some flushing and then do some calmag.

 

[richrich]

Let me check the soil/water PH and I'll get back to you in few hours. Thanks for responding though! I hope its not some kinda pest issue..

 

[Papageno]

Yes the spotting is a pH issue that probably built up over time or is due to over watering. By watering before the bottom of the pot drys you can create rot in the bottom and that will mess up the pH.

Probably not rot yet and it isn't too hard to fix if it were.

What is hard is the Nitrogen overdosing causing the saggy curled droopy plant. Google something like "Cannabis Nitrogen Toxicity". Most common thing people mess up.

It would be a good idea to get a few buckets of pH'd water and run it through the pot to flush it out. 5 times the pot size would be a good start. In the last gallon mix in some enzyme.

Then let the pot dry before watering again. At some point it wont be enough and you may need to up size that pot.

 

[MrRudeSnowman]

Yeah the watering thing. Water only when it's bone dry... the basics man.

 

[richrich]

I just checked the PH of the tap water I've been feeding.. its 7.1

I've made more holes in my pots so that roots can get more oxygen. Drained some fresh water turned all the soil once from bottom to up.

Do you know if/how they will rejuvenate back to normal? Is there anything else I can do as of now?

 

[Papageno]

They will come back fine if properly handled. You will loose some fan leaves but let the plant steal as much back as it can first. Only remove them if they are in the way blocking growth and wait till they come off by hand. They will come back a lot though. Many will recover enough to look decently nice.

I mentioned the water because in the beginning you said you only waited for the first few inches to be dry.

 

[MrRudeSnowman]

It can still be worth growing, but look to it more like learning experiment. Don't expect a whole lot from it. Try testing runoff water after flushing next time. It should be 6,3-6,5 for best results. You probably need to lower ph of your water. What soil did you use?

 

[richrich]

I used black soil with coco peat mixed. Its been 2-3 days since first flush. So I flushed them again today and now I can see some of them picking up again. couple of them almost dried up. Lets see how they come up in next few days. I hope they will make back.

Thanks so much MrRudeSnowman & VilliageIdiot for your advice! I'll keep you posted with new pics in next couple days.

 

[richrich]

Hello everyone,

Short update and help needed:

Half of my plants dried anyways even after taking alot of care about the soil PH, humidity and not letting the root rot happen. I am still kinda puzzled what else I could have done?

Please see the pictures below. The ones which are still green are kinda partly sick I guess cuz they dont show any growth since over 10 days now. ANd trying to fall. I am now letting the soil dry 100% before I water them but still they aren't seemingly picking up. Please let me know if theres anything else I can do.

Thanks!

 

[Papageno]

root bound...


The healthier looking plants have a reasonable amount of soil for ones that should be bout half their size going into bloom. You have some plants there that are rather tall in pots that are half filled that are barely big enough to begin with.

Get yourself some big fabric pots and transplant everything.

 

[MrRudeSnowman]

Not all damage can be repaired, keep that in mind. Spots & curls can stay that way forever even if you fix what can be fixed.

It still looks to me like a heat stress and nutrient toxicity (too much nutes with wrong PH).

What does black soil means? I bet that's the problem.

How did you took care of the PH? What is the PH level of the water you use and runoff water? Let's say you use water of PH6,5 and what comes out the other end is PH5 means you are doing it wrong. Got it?

 

[richrich]

Hi MrRudeSnowman,

The black soil I used is the soil used in organic fields to grow vegetables and food. I took care of PH by running 7 PH water through the pots and only adding very little nutrients to last bucket of water I used for runoff.

From your comment, what I understand could be a problem is I didn't measure the PH of the last runoff water. I just ran through them a few buckets (3-4 times the size of their pots). And I did this twice a week.

 

[Papageno]

Cannabis is a plant that prefers to have the roots dry out. You are watering too much too often. The yellowing is becasue you are running out of nutes. you are flushing it all out the bottom.

Not more than 25% runoff. I usually shoot for 15%

Do not water until the pot is light. The top of the soil being dry is not enough. If you keep it wet worst case is it will rot at the bottom and kill the plant. There are many other things that being over watered cause including smaller plants and if continued through bloom lower yields.

I personally don't water until the plant begins to show signs of lack of water as that stimulates excessive unnecessary root growth which makes things better for the plant. They grow bigger and faster that way with stronger bigger roots.

 

[MrRudeSnowman]

Well you have to let your pots dry up and test runoff water in at least one of them if soil is the same. PH of the water has to be lower that 7!!! If it's precisely 7 there will be problems. See if you run 7 through your pot and what comes out is not 6,2-6,5 you are no good.

 

[baxbax]

im 100% sure u have root bound - i guess its root bound from first picture but its clear u have root bounded plants in your last picture - just transplant them and they will be fine

 

[richrich]

I found out what the real cause was.. This soil had mud and some cowdung mixed in it.. There were few small cowdung bits holded by roots which were sending a ton of nutrients which should have caused the the problem in the first place. And the water I was running off was just fine however the cowdung has been so sticky that roots were totally binding that and were not able to get rid of it.

Today I changed the whole soil with coco peat and washed off all the roots. Hopefully now all should be able to recover. I think I am too late to do it but I am hopeful now.

Thanks to you both for helping me realize again.

 

[richrich]

im 100% sure u have root bound - i guess its root bound from first picture but its clear u have root bounded plants in your last picture - just transplant them and they will be fine

I agree that could also be the reason but if thats the one, how does people get huge yields growing in smaller pots than even mine all the time? I would like to learn that art too.