Discolouration on leaves

[zen-ken]

43 minutes ago, David Attenborough said:

Thats way too much,

 

 

 

(sorry....just yanking your chain...I meant no insult)

Edited October 19, 2023 by zen-ken

[zen-ken]

Light burn doesn't look like that and it would be on the tops not the middle...its a calcium problem

 

Down to the roots or an imbalance in feeding being shown up more by the increase in PAR.

I wouldn't use PAR of the measure of light you put down tbh.....PPFD and DLI are much better ways of measuring.

 

18hrs of 700 PAR and 12hrs of 700 PAR give you very very different DLI/PPFD readings 

 

 

Calcium Deficiency

 

Credit :by Nebula Haze & Sirius Fourside

Problem: Calcium is an important nutrient that helps provide structure to the cannabis plant and helps it withstand stress like heat. When your cannabis plant has a calcium deficiency, the main symptom that you’ll be able to notice is brown or bronze splotches or spots on your leaves. It is also often associated with yellowing (though leaves don’t always turn yellow). Occasionally the splotches may appear purple especially under LEDs. Calcium deficiencies are often caused from low pH at the roots, but also occasionally from growing in soft/filtered water.

Calcium deficiencies are often associated with yellowing in addition to the brown spots, (though not always!). This is an example of the beginning of a calcium deficiency that has yellowing in addition to the brown spots.

Calcium deficiencies are common when growing in coco or using soft or filtered water, but the most common reason to see a calcium deficiency is low pH at the roots

Here’s another example of a calcium deficiency caused by low pH. Symptoms are typically worse on the leaves at the top of the plant and close to the light.

These plants grown in soil are suffering from too low pH at the roots. Although cannabis calcium deficiencies are more common in coco, they can appear in soil and hydro, too

 

This deficiency is most common in the flowering stage after buds start forming (though you may see it any time)

A cannabis calcium deficiency can sometimes be difficult to diagnose since calcium deficiencies are often accompanied by magnesium, iron, and/or other cannabis deficiencies.

It can also be confusing because calcium deficiencies may look different on different strains

Under LED grow lights, calcium deficiencies may even appear purple at first. Later in the flowering stage, it’s normal for leaves to become more colorful, but if all the hairs are still white it’s too early for leaves to be discolored (leaves that lose their green too early can’t photosynthesize as well which can reduce yields). Normally when you see something like this it’s because the pH is too low.

Calcium moves relatively slowly through the plant (it is a semi-mobile nutrient), which means it tends to “stay put” after it’s been given to a leaf. It tends to show up on leaves that are actively growing and getting some amount of light.

Calcium deficiencies most often show up in the following places:

• Newer growth (upper leaves)
• Parts of fan leaves that have been exposed to the light

Found near the top of the plant under the light

This lower fan leaf is mostly in the shade, but the calcium deficiency appears near the edges that are getting light. Calcium deficiencies often show up on parts of the leaf that are still actively growing.

Calcium Deficiencies Appear on New or Actively Growing Leaves

Calcium deficiencies tend to appear on newer or growing leaves, which means calcium deficiencies first appear on leaves where there’s rapid vegetative growth.

Some of the most noticeable signs of a calcium deficiency will appear on newer or growing leaves which may display:

• Dead spots
• Crinkling
• Spotting / Mottling
• Small brown spots
• Stunted growth
• Small or distorted new leaves
• Curled tips
• Leaf die-off
• Affected leaves may appear green besides the spots

Here’s a close-up of a calcium deficiency that appeared on leaves towards the top of a cannabis plant grown in coco coir:

Other Symptoms of Calcium Cannabis Deficiency

If a cannabis plant is affected by a calcium deficiency for too long, it may begin to show the following symptoms due to the lack of calcium.

• Stems become weak or flimsy and may crack easily
• Stems become hollow or show inner signs of decay
• Plant does not stand up well to heat
• Flowers/buds do not develop fully, or development is slow
• Roots appear weak or under-developed
• In severe calcium deficiencies, parts of roots may even die off or turn brown
• Roots are more susceptible to root problems like slimy root rot

Cannabis tends to like high levels of calcium, so it is unusual to feed too much calcium when using normal amounts of nutrients and/or regular soil. There are not many known cases of cannabis calcium toxicity (too much calcium), however too much calcium can cause the plant to lock out other nutrients, so it’s important not to go overboard..

Calcium deficiencies are more likely to appear when…

• Grower is using filtered or reverse osmisis (RO) water to feed plants – the amount of calcium found in tap water varies, but some tap water has enough calcium to prevent calcium deficiencies
• PH is Too Low – If grow medium is acidic (below 6.2 pH, Calcium can get locked out even if the Calcium is physically there)
• Growing cannabis in hydroponics or coco coir without supplementing extra Calcium (it’s recommended to use a Calcium supplement in hydro or coco)
• When growing in soil that hasn’t been supplemented with calcium (usually from dolomite lime)
• Too much potassium can also sometimes cause the appearance of a calcium deficiency
• Outdoors – calcium deficiency is more likely to appear in acidic soil (below 6.2 pH)

Different strains of cannabis tend to have different nutrient problems. Some cannabis strains (or even specific plants) tend to use much higher levels of calcium than others, and so you may see calcium deficiency problems with one plant even when all the other plants (which are getting the same nutrients and environment) aren’t showing any signs of deficiency.

 

Solution For Calcium Deficiency in Cannabis

Your cannabis plant may show signs of a calcium deficiency if the pH at the roots is too low. That is because when the pH of your root zone is too acidic, your cannabis cannot properly absorb calcium through its roots. Therefore the first step is to ensure that you have the correct pH for your growth medium.

Too low pH is the MOST common reason for a calcium deficiency to appear

Please note: After a calcium deficiency is cleared up, the problem (brown spots and unhealthy new leaves) will stop appearing on new growth, usually within a week. Please note that leaves which have been damaged by a calcium deficiency will probably not recover or turn green, so you want to pay attention to new growth for signs of recovery.

• In soil, calcium is best absorbed by the roots in the 6.2 – 7.0 pH range (in soil, it’s generally recommended to keep the pH between 6.0 – 7.0, but calcium specifically tends to be best absorbed above 6.2)
• In coco or hydro, calcium is best absorbed by the roots in the 6.2 – 6.5 pH range (in coco/hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but calcium specifically tends to be best absorbed above 6.2)

If you suspect your growing cannabis plant has a calcium deficiency, flush your system with clean, pH’d water that contains a regular dose of cannabis friendly nutrients that includes calcium. This will remove any nutrient salts that may be affected the uptake of calcium and help restore pH to the proper levels.

Cal-Mag Supplement

To supplement with extra Calcium… (it’s very rare to give a cannabis plant too much calcium, however, too much calcium can lock out other nutrients so don’t go overboard)

Calcium and magnesium deficiencies often appear together in cannabis. Many growers decide to purchase some sort of Calcium-Magnesium (often called Cal-Mag) supplement for their grow room in case this common deficiency appears.

After supplementing with Cal-Mag and correcting the pH, you should expect to see new healthy growth within a week. Remember, the old leaves will probably not recover, but new growth should be green and healthy.

Dolomite Lime – For Soil Growers (Organic)

If you’re looking for a way to supplement calcium in your organic or soil setup, I highly recommend a product called “Dolomite Lime.”

Dolomite is a good source of calcium and magnesium and can be mixed with your soil. The great thing about dolomite is it works slowly over the course of a few months.

Dolomite has a neutral pH of about 7.0 and will help keep soil at the correct neutral pH range which is optimum for cannabis growth.

 If possible, try to get a finer grade of dolomite compared to something that is more coarse.

How to Use Dolomite Lime for Cannabis: When growing cannabis indoors, add 6-7 teaspoons of fine dolomite lime to each gallon’s worth of soil. So if you’re mixing enough soil to fill a 5 gallon container, you want to add 30-35 teaspoons (about 2/3 cup) of dolomite lime to the mix. Mix the dolomite lime and the dry soil thoroughly, then lightly water it with water that has been pH’ed to 6.5. After getting the soil wet, mix the soil well and wait a day or two to let the soil settle before checking the pH and adding plants. When growing in an outdoor garden, follow the dolomite lime manufacturers instructions

 

Credit Nebula Haze and Sirius Fourside

 

Edited October 19, 2023 by lildaveham
removing the links

[zen-ken]

Edited October 19, 2023 by zen-ken

[Satchitananda]

@zen-ken It does look more like calcium deficiency. Thanks man.

 

I will lower the light for now anyway AND I will give em some CalMag next feed. Or maybe I could foliar feed some CalMag now?

[zen-ken]

Just now, Satchitananda said:

@zen-ken It does look more like calcium deficiency. Thanks man.

 

I will lower the light for now anyway AND I will give em some CalMag next feed. Or maybe I could foliar feed some CalMag now?

 

You don't need to lower the light....I have seedlings under more light than your giving them.....And Im running 24/0

 

Wait till lights out and get the foliar feed on the go....once will probably do it.....I only feed silicon, Calcium and Magnesium once a week on foliar. (The Ca/mg if needed...but silicon religiously till early bud set)

 

Are you using a potassium heavy feed by any chance ?

[GSZZ]

3 hours ago, Satchitananda said:

Temps are about 26-28c lights on and 20c lights off.

 

Lets not complicate beans on toast lads, the issue isn't a mineral imbalance its cold roots.

[Satchitananda]

Just now, GSZZ said:

 

Lets not complicate beans on toast lads, the issue isn't a mineral imbalance its cold roots.

 

 

You didn't quote the sentence after that one that said "I have a heat mat keeping the roots at 23c"?

[zen-ken]

Just now, GSZZ said:

 

Lets not complicate beans on toast lads, the issue isn't a mineral imbalance its cold roots.

Yeah...tbf....I did beat around the bush to get to the 'root' of the problem  

 

I have no idea why all you coco and soil growers don't have the soil/coco at 25C

It's not like you have to worry about pythium is it ?

 

I keep 20C cause I have to........not cause I want to 

 

Edited October 19, 2023 by zen-ken

[zen-ken]

2 hours ago, zen-ken said:

 

I wouldn't use PAR of the measure of light you put down tbh.....PPFD and DLI are much better ways of measuring.

 

Please excuse me here.....you were in PPFD.....I had a massive blonde moment there didn't I 

[Satchitananda]

Just now, zen-ken said:

Please excuse me here.....you were in PPFD.....I had a massive blonde moment there didn't I 

 

 

 

[Satchitananda]

I will turn the heat mat up to 25c AND foliar feed them CalMag (actually PM MagneCal) AND introduce a third tube heater for lights out.

 

Thanks everyone.

[GSZZ]

Just now, Satchitananda said:

You didn't quote the sentence after that one that said "I have a heat mat keeping the roots at 23c"?

 

Is that an actual pot reading though or is it just what you've got the jobbie set at? Or an air temp reading? You weren't clear - 20c air temps would usually suggest that roots/plant is cold anyway. Always remember that air and actual temps are two very diff things.

 

Calciums uptake is controlled by transpiration and magnesium availability - you'll never not have enough calcium in solution/soil/tap combined, but you might not have enough mag. Raising potassium also increases magnesium demand, and can leave not enough for sufficient uptake of calcium like zen ken mentioned - but your pots looked dry in the first post, if its not cold roots, it'll probably be how you're watering them - i'm confident the issue here isn't imbalance.

 

Just now, zen-ken said:

Yeah...tbf....I did beat around the bush to get to the 'root' of the problem  

 

 

Just now, zen-ken said:

have no idea why all you coco and soil growers don't have the soil/coco at 25C 

It's not like you have to worry about pythium is it ?

 

I keep 20C cause I have to........not cause I want to 

 

Mine are regularly at 25c or above, 28c night and 30c days, moving to 26c nights and 28c days as flower moves on.

[Satchitananda]

Just now, GSZZ said:

 

Is that an actual pot reading though or is it just what you've got the jobbie set at? Or an air temp reading? You weren't clear - 20c air temps would usually suggest that roots/plant is cold anyway. Always remember that air and actual temps are two very diff things.

 

Calciums uptake is controlled by transpiration and magnesium availability - you'll never not have enough calcium in solution/soil/tap combined, but you might not have enough mag. Raising potassium also increases magnesium demand, and can leave not enough for sufficient uptake of calcium like zen ken mentioned - but your pots looked dry in the first post, if its not cold roots, it'll probably be how you're watering them - i'm confident the issue here isn't imbalance.

 

 

 

 

Mine are regularly at 25c or above, 28c night and 30c days, moving to 26c nights and 28c days as flower moves on.

 

Thanks for explaining.

 

 

The pots aren't dry, the are still quite heavy.

 

They haven't received any feed so they haven't received too much Potassium.

 

The 23c is measured by the thermostat probe which is stuck into the soil at the bottom of the pot.

 

 

[GSZZ]

Just now, Satchitananda said:

The pots aren't dry, the are still quite heavy.

 

Well a calcium problem can show if the pot is too dry or too wet - something I see sometimes with soil growers (and coco growers, too) is they take the wet/dry cycle a bit too literally and really wait for the medium to properly dry out before really soaking the pots, duing which time, the actual time the plants are transpiring and photosynthesizing is actually only a small period of time between them starting to transpire after a water and them stopping again. In some cases with soil growers, thats a whole lights on period or two the plants aren't transpiring/limited transpiration and that calcium isn't getting where it needs to be!

Edited October 19, 2023 by GSZZ

[Satchitananda]

@GSZZ thanks again.

 

They have only been watered once in these pots, that's when I potted them up the other day...it's possible I soaked them a bit then. Maybe I should have been more reticent with the ol' watering can?