Any idea what's doing this to the leaves?
- Thread starter dba1954
- Start date
Could be too much light, sometimes it shows on the older leaves first. The plant is really young to have deficiency issues. Back the lights off a bit and see if it doesn't stop. If it continues then start mild feeding.
- Thread starter
- #3
Those look like spots from a building calcium deficiency. Cal/mag is the usual go-to for that.
Delps8
Well-Known Member
I don't see anything in the pictures that indicates too much light and 20k lux is a modest amount of light for a plant of that age.
20k lux is about 300µmol which is a good level for seedlings. Given the size and age of that plant, I'd increase the light level by 10k per day for a few days. I grow in hydro so the plants tend to grow quickly but, at four weeks, I'm generally at 65k lux. This plant is looks to be well developed but I really can't tell - more photos of the plant would help.
If your plant was receiving too much light, the leaves closest to the light would be the first to react. The leaves at the top are getting more light than the leaves toward the bottom of the plant and they're younger so their ability to photosynthesize is not as well developed as the more mature leaves that are lower in the canopy and that are getting less light.
When leaves receive too much light, the most common reaction is to curl up their edges so as to reduce the leaf surface that was being exposed to light (canoeing or tacoing) or sometimes the leaves rotate around their stem (a "petiole") in the same way that a Venetian blind can be turned.
The reflexive action to "turn down the light" is common and is akin to "My kid twisted his ankle so I took away his lunch." Light is the only way that plants get food. When you reduce the amount of light, less food is produced, and growth slows.
The leaves in the top photo look like they've had nutrient water dropped on them. Any chance, you dropped nutrient water on them?
The leaves that are showing some light discoloration looks to be the beginning of a nutrient issue. If it's a magnesium deficiency, that could be a result of something that you changed 7-10 days ago. Anything come to mind that you changed back then?
Nutrient issues don't "just happen". Cannabis grows quite well in fairly wide ranges of the chemicals that make up nutrients. If you mix your nutes incorrectly, that can cause an issue. Some strains are more susceptible to nutrient issues, as well. Many times, the nutrient issue is not because of a lack of X but could be too much of Y or an environmental issue.
How are you measuring your light levels? What light are you using and what's the hang height, dimmer setting, and lighting schedule?
Many nutrient issues are because temperature and RH are high. What is the temp in the tent and what's the RH?
Do you have a fan running in the tent?
It would be helpful if you posted a picture of the whole plant in the tent, too.
20k lux is about 300µmol which is a good level for seedlings. Given the size and age of that plant, I'd increase the light level by 10k per day for a few days. I grow in hydro so the plants tend to grow quickly but, at four weeks, I'm generally at 65k lux. This plant is looks to be well developed but I really can't tell - more photos of the plant would help.
If your plant was receiving too much light, the leaves closest to the light would be the first to react. The leaves at the top are getting more light than the leaves toward the bottom of the plant and they're younger so their ability to photosynthesize is not as well developed as the more mature leaves that are lower in the canopy and that are getting less light.
When leaves receive too much light, the most common reaction is to curl up their edges so as to reduce the leaf surface that was being exposed to light (canoeing or tacoing) or sometimes the leaves rotate around their stem (a "petiole") in the same way that a Venetian blind can be turned.
The reflexive action to "turn down the light" is common and is akin to "My kid twisted his ankle so I took away his lunch." Light is the only way that plants get food. When you reduce the amount of light, less food is produced, and growth slows.
The leaves in the top photo look like they've had nutrient water dropped on them. Any chance, you dropped nutrient water on them?
The leaves that are showing some light discoloration looks to be the beginning of a nutrient issue. If it's a magnesium deficiency, that could be a result of something that you changed 7-10 days ago. Anything come to mind that you changed back then?
Nutrient issues don't "just happen". Cannabis grows quite well in fairly wide ranges of the chemicals that make up nutrients. If you mix your nutes incorrectly, that can cause an issue. Some strains are more susceptible to nutrient issues, as well. Many times, the nutrient issue is not because of a lack of X but could be too much of Y or an environmental issue.
How are you measuring your light levels? What light are you using and what's the hang height, dimmer setting, and lighting schedule?
Many nutrient issues are because temperature and RH are high. What is the temp in the tent and what's the RH?
Do you have a fan running in the tent?
It would be helpful if you posted a picture of the whole plant in the tent, too.
- Thread starter
- #6
- seedling was transplanted into a 3 gallon container. 8/25. It had 4 nodes.
- 8/29 I increased the light intensity from 7,000 lux to 20,000 lux
- The soil is foxfarm ocean and was used in both the containers, same bag.
- No nutrients had been given to the plant, just distilled water. Actually we did just start yesterday per directions for foxfarm nutrient trio
- temp is around 78f, humidity between 45% and 55%
- i have a fan running as well as and exhaust fan/filter
- plant strain in Northern Lights
- 9/4 I fimmed at the 7th node, not sure if it took yet
- i noticed the discoloration 9/6
- The lights are a pair of Mars Hydro TS1000'S at 28" high
- tent is a 3'x3' x72"
- I'm using a Digital LUX Meter LX-90 Light Meter with LCD Display, Range 0-100,000 Lux to measure intensity
thanks for the help !
Plants are looking good so far except for those minor leaf spots.
With the first dose of fertilizer being yesterday (09/06/24) it will be a several days to as long as just over a week or two to tell if it is making a difference. There is a chance you will still see some new spots or changes in color on the leaves developing while waiting for the plant to absorb the nutrients available in the Fox Farm trio.
To be able to tell if the fertilizers are helping is that new spots, etc do not keep showing up. Any existing spots will be there forever. As long as the damage is minor and the leaf remains healthy it can stay on the plant.
@dba1954, it is best to buy a separate bottle or bag of a Calcium-Magnesium product. Follow the dose and schedule found on the package. I don't remember if any is included as one of the ingredients in the trio. Even if it is it will be a minor amount.
The Fox Farm trio is a good choice. For best results the grower should follow the most recent schedule as found at the web-site or by asking Fox Farms to mail a copy or sometimes available at grow & gardening shops.
With the first dose of fertilizer being yesterday (09/06/24) it will be a several days to as long as just over a week or two to tell if it is making a difference. There is a chance you will still see some new spots or changes in color on the leaves developing while waiting for the plant to absorb the nutrients available in the Fox Farm trio.
To be able to tell if the fertilizers are helping is that new spots, etc do not keep showing up. Any existing spots will be there forever. As long as the damage is minor and the leaf remains healthy it can stay on the plant.
It does look like a need for cal-mag.
@dba1954, it is best to buy a separate bottle or bag of a Calcium-Magnesium product. Follow the dose and schedule found on the package. I don't remember if any is included as one of the ingredients in the trio. Even if it is it will be a minor amount.
Delps8
Well-Known Member
Great info and excellent pictures of a really nice looking plant.
Congrats on using a light meter. It's a valuable tool for a cannabis grower.
Soil - don't know much about the subtleties of soil but you've got a nute imbalance. I suspect that it's a function of VPD being a bit too high.
If you're not familiar with VPD, this is a good source. VPD ("vapor pressure deficit") is analogous to "feels like" temperature for humans. 78°F is an OK temperature for cannabis (though it's on the cool side for optimal growth in veg) but, the 45-55% RH is a bit dry. Putting the two numbers together and your plant is transpiring quite a bit.
In humans, it's OK to be in low humidity but we will drink more water. Plants react in a similar manner - they "transpire" more. And when they transpire more, they have to take up more water. The idea of a vapor pressure deficit is that there's a difference in pressure between the leaves (which are full of water) and the air outside. When the air around the plant is dry, water must leave the plant simply because that's the way "things" work. Energy flows from high energy state to low energy state (things "cool off"). Water flows down hill because of gravity. Etc, etc. When it's dry on the outside of a plant, the water will leave the plant.
And when water leaves the plant (pardon the pun), water will flow into the plant via the roots. Chemicals ("nutrients") are brought in when the water enters the roots. Again, moving from high to low.
When you VPD is 1.5'ish, per the screenshot below, your plant is taking in about 33% more water than it is when VPD is 1.0 (that's a good VPD for veg).
I'm not saying that is what's causing the nutrient issue but, if it was my plant, I'd get raise the RH ASAP and increase the amount/frequency of water, if that's OK to do (I'm not a soil grower).
Re light levels - I've attached a document I've written on converting lux to PPFD. Lux reads a different spectrum of light than plants do, so you can convert a lux reading to a PPFD value which indicates how much PAR the plant is getting. The TS 1000 light is a tiny bit more blue than a "standard" white LED so, according to Mars, the conversion factor is 0.0147.
At 20k lux, your plant is only getting 280µmol. I think you said it was 4 weeks? A plant that age could be at almost three times that level of light. At only 280, your plant is not getting much light at all - truly in seedling territory. Having said that, it looks great. Beautiful color, good foliage but seriously underfed.
Yield may not be all that important and each grower has their own goals for their crop. If you want to maximize yield and quality, your light levels need to increase. There's no reason to not raise your light levels 10-15k per day. Cannabis is more than happy to go from 300µmol to 450 to 600 etc. but my experience is that grower's are hesitant. Your plant is pretty close to mature in terms of its ability to process light. It's not fully grown but the leaves' ability to photosynthesize is very highly developed by 28 days so, from the perspective of the plant, it's wondering why it's on a diet!
Each time you increase your light levels, check your plants, looking for a physical reaction to the light increase. The first few times you increase the light levels, I don't think you'll see any negative reaction. The signs of excess light are that the plant will change shape so it will reduce the leaf area that's exposed to light. It does this by curling the edges ("canoeing") or rotating the leaf vertically around the petiole, in the same way that a Venetian blind turns vertical.
Note my comment "I don't think" - I've seen two grows where plants could not handle 500µmol, which is about ½ of the level where most cannabis maxes out. The issue turned out to be that the growers hadn't watered properly and the soil was hygrophobic. The hard, dry clumps of soil in the subsurface made it impossible for the roots to grow properly and the plant hit its limit at 500. A cannabis plant in a good grow environment will thrive at 800-1kµmol of PAR.
I believe that your plans have a nutrient imbalance because your RH is low. If you increase RH and/or water a bit more, I think you'll see the issue resolve. Adding more light will help you get the most from your grow.
- Thread starter
- #9
I've increased the light to 30,000 lux and added calmag to the feeding. RH I'm not able to control at this time, it is what it is for now. The watering can't be increased or I will run into other issues. I wait till the soil is fairly dry to avoid root rot. The foxfarm soil holds water pretty good so I only water about every ~5 days. As the plant grows the frequency will increase.
i hope this turns around, I will keep you posted and thanks to everyone for helping
i hope this turns around, I will keep you posted and thanks to everyone for helping
- Thread starter
- #10
A few more leaves showing spots as expected but the plant is noticeably darker green. The temp in the tent is now 81F with the increased lux. I started calmag this morning with my watering so keep my fingers crossed.
- Thread starter
- #11
so i picked up another temp/humidity gauge with wifi. Temps get up to 84 during the day now, 42% humidity and at night 71f and 61% humidity. Guess I need to work on controlling that. The FIM didn't take so i did it again. No new leaf spots since starting feeding and calmag. The plant is growing fast growing almost 2" over the last 3 days.
Just reading through here, and I noticed you are using distilled water! There's your problem! Distilled water has no micro nutrients and no chelated minerals. You would be better off with spring water. I use my tap water, for almost 20 years now!
- Nutrient deficiencies
Using distilled water alone can lead to nutrient deficiencies. - Removes minerals
Distillation removes minerals that are good for plants, which can lead to stunted growth and discoloration over time.
Good luck to you
Ditto on Mocha
Saw this earlier today, meant to comment but had to leave
Distilled strips the good stuff out of water, it’s not optimum for people, pets or plants
84 is lights on target temp but you want high rh in veg and lower rh in flower to avoid bud rot & pm
Saw this earlier today, meant to comment but had to leave
Distilled strips the good stuff out of water, it’s not optimum for people, pets or plants
84 is lights on target temp but you want high rh in veg and lower rh in flower to avoid bud rot & pm
- Thread starter
- #14
Delps8
Well-Known Member
40k lux is about 600µmol. Cannabis thrives at the light saturation point of 800-1000µmol, strain dependent. I routinely grow plants >1000µmol.i seem to have it back on track @40,000 lux. I will need to address the temperature, possibly use only 1 light
At your current light level, you're "losing" about 25% of your potential yield.
"Growers lose more of their crop by not giving their plants more light than they do by giving their plants too much light." <===this is going in my signature block.
- Thread starter
- #16
i am somewhat limited by my lights. The plant is growing fast and i really don't want to be moving the lights daily. once it gets to full height and stops growing I'll bring it up to around 65,000. when I say 40,000, I mean 40-55,000 as the plant grows. I don't need to maximize yield, it's just for me, I'm north of 70 and dont smoke a lot but thanks
Delps8
Well-Known Member
i am somewhat limited by my lights. The plant is growing fast and i really don't want to be moving the lights daily. once it gets to full height and stops growing I'll bring it up to around 65,000. when I don't need to maximize yield, it's just for me, I'm north of 70 and dont smoke a lot lol
"I'm north of 70 and dont smoke a lot lol
"I'm hitting 68 next month and I don't smoke anymore so I understand completely.
Even at 600µmol, if your environment is good, cannabis produces a lot of weed. Since I've never grown anything else, it's really amazing to see.
- Thread starter
- #18
Delps8
Well-Known Member
Check the VPD chart I posted earlier.
79 and 50% is a VPD of 1.5 which is on the high end for plants in flower. This plant is in veg and will do best at a VPD of 1.0, all other things being equal.
At 1.5, your plant is transpiring at a 50% higher rate than it is at 1.0. If you feed your plants the same nutrient concentration when they're taking up 50% more water, they will take up more nutrients and that will tend to create nutrient imbalances.
The options - do nothing; decrease temp and/or increase RH; decrease EC of the nutrients.
79° is a but below optimal temperature for veg so I wouldn't lower it.
79 and 50% is a VPD of 1.5 which is on the high end for plants in flower. This plant is in veg and will do best at a VPD of 1.0, all other things being equal.
At 1.5, your plant is transpiring at a 50% higher rate than it is at 1.0. If you feed your plants the same nutrient concentration when they're taking up 50% more water, they will take up more nutrients and that will tend to create nutrient imbalances.
The options - do nothing; decrease temp and/or increase RH; decrease EC of the nutrients.
79° is a but below optimal temperature for veg so I wouldn't lower it.
- Thread starter
- #20
I don't have a way to properly control humidity and I've trying to keep temps as indicated below. btw, i'm at most 10-11 days from changing to flowering. If you say the plant is probably taking up too much nutrients they I can maybe feed them once a week. So you think this is not a fungus or other issue?
(Cannabis Temperature Tutorial | Grow Weed Easy)
(Cannabis Temperature Tutorial | Grow Weed Easy)
