Black spots on my leaves

I have been high stress training this plant and just leave stripped and cleaned up the lower branches. These plants are outside in a hoop house. I water with PH levels between 6.5 and 6.8 and am using organic dry nutes. I feed every couple of weeks with 4-4-4, worm castings and have added 0-11-0 bird guano as a top dress. I watered this morning and didn’t notice anything. This evening I saw this problem. I started this from seed given to me out of a freebe that he didn’t want to grow. It was labeled “bruce banger”. This plant is in with two other photos and one auto. I had bud rot on one of my plants last season on one branch, and was able to bag it and save the rest.
I would like to know if I need to take this robust girl down and out, or if there is hope to save her.

Here is a better picture

I’m thinking that I may have a nutrient deficiency. It is just beginning to show flowers, but i have a few months until harvest and freezing temps. Any suggestions would help.
This is what it looks like today. Anyone??


Might be a Cal-Mag deficiency

Plant overall looks fine; a bit light in color but that could be the plant. That looks more like possible mildew or ‘rust’: does it rub off?

It’s possible a dose or two of cal mag would help: wouldn’t hurt for sure.

Thanks for the reply! No, it does not rub off. Its in the leaves. I will try cal mag ASAP!

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Looks like Manganese deficiency. Currently dealing with it myself. Check soil PH if you can. If soil PH is too high above 7.0 that’s when plant stops uptaking manganese. Need to lower soil ph with a flush. You can also try a foliar spray with Manganese. Mines not as severe as yours but here’s a pic.

This was posted by @garrigan62
First I want to welcome you to ILGM. Sorry I didn’t get here sooner but I had to take a few days off.
Any way your plants problems seem to be…

Manganese (Mn)
Micronutrient and Immobile Element

Here are a couple of pic’s that look just what your plants are going through.



Manganese Helps enzymes break down for chlorophyll and photosynthesis production,
as well as it works with plant enzymes to reduce nitrates before producing proteins.

Having plants that are deficient in manganese can turn the young leaves into
spotted (mottled) yellow and or brown areas on young leaves. Dead (Necrotic)
yellow spots form on top leaves, while the lower older leaves will or may have
gray specks and or spots. Symptoms can include yellowing of leaves while the
leaf veins can stay green. Can also produce a chequered effect. As the plant
gets newer growths the plant will seem to grow away from the problem, that’s
why the younger leaves may be unaffected. On the top of the leaves, brown spots
can appear. While the severe areas of the leaves turn brown and wither.
Parts Affected by a Manganese deficiency are: Young leaves.

Too much Manganese in the soil will cause an iron deficiency. The blotchy leaf
tissue is caused by not enough chlorophyll synthesis. Your plants will seem to
have very weak vigor caused by the excessive amount of manganese.

Problems with Manganese being locked out by PH troubles

Soil ph of over 6.5, High iron soils, Low nitrogen Soils, Dry weather
and compacted soil.


Manganese gets locked out of soil growing at ph levels of 2.0-5.0
Manganese is absorbed best in soil at a ph level of 5.5-6.5 (Wouldn’t recommend
having a soil ph of over 7.0 in soil) anything out of the ranges listed will
contribute to a Manganese Deficiency.

Hydro and Soil less Mediums

Manganese gets locked out of Hydro and Soil less Mediums at ph levels of 2.0-4.5
Manganese is absorbed best in Hydro and Soil less Mediums at ph levels of 5.0-5.6
(Wouldn’t recommend having a ph over 6.5 in hydro and soil less mediums.) Best range
for hydro and soil less mediums is 5.0 to 6.0. Anything out of the ranges listed
will contribute to a manganese deficiency.

Solution to fixing a Manganese deficiency
Foliar feed with any chemical fertilizer containing Mn., or mix with water and water
your plants with it. Any Chemical/Organic nutrients that have Manganese in them will
fix a Manganese deficiency. (Only mixing at ½ strength when using chemical nutrients
or it will cause nutrient burn!) Other nutrients that have Manganese in them are:
Manganese chelate, Manganese carbonate, Manganese chloride, Manganese dioxide,
Manganese oxide, Manganese sulfate, which are all fast absorption. Garden Manure,
Greenssand are both good sources of manganese and are medium/ slow absorption.

Now if you added to much chemical nutrients and or organics,( which is hard to burn
your plants when using organics) You need to Flush the soil with plain water. You need
to use 2 times as much water as the size of the pot, for example: If you have a 5 gallon
pot and need to flush it, you need to use 10 gallons of water to rinse out the soil good
enough to get rid of excessive nutrients.


Thank you for the input. I do not currently have a way to test PH of the soil.
I have been using dry organic nutes, and only feed every couple of weeks topdressing and working into the soil. I will look into a manganese supplement also.
I find it strange that I am having this problem with only one of my plants, the bruce banger. The Jack Herer plants look great, and all are in the same soil, same feeding, and same water, pots, house, etc.

I think you mean Magnesium. That’s a classic Mg def shown.

The other thing is you may have had a ‘departure’ from nominal grow conditions at some point which caused this and the plant is now showing the result. You can’t look at this growth as it’s already damaged, to determine if you have solved it you need to look to new growth for improvement.

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@Myfriendis410 OK thanks for clarification. So does this look the same?

Interveinal chlorosis, bronzing of leaves: cal mag def.

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Thanks. She’s been getting 5ml of calmag every feeding. What might be causing this then?
I have another plant not same strain but planted same time only in kind soil and she’s doing fantastic.
Could this be overfeeding?

It could be any number of things. A deficiency or excess, PH out of range, genetics always plays a role etc.

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@Myfriendis410, @Deepsix, @registereduser Just a quick update. I have changed the PH of my water (shooting for 6.2 to 6.5) and introduced cal mag. All the new growth is looking healthy and the rapid discoloration has stopped! I understand that the damage on the affected leaves will not be repaired.
A HUGE THANK YOU to you guys! You have put my mind at ease, and my grow back on track! This community ROCKS!!