Plant Moisture Stress - Symptoms and Solutions

PLANT MOISTURE STRESS - symptoms and solutions (revised Jan. 12, 2009)

Quite often I hear groans from folks having leaf problems -> “Help, my leaves are cupping and the leaf edges are turning brown!”, or, “My plant's leaf tips are curling down and turning black ....what's wrong?” Unless insect damage has occurred or the plant is suffering from a severe case of calcium deficiency, the plant is trying to tell you that it is water stressed. It's hard to tell *exactly* what the culprit is, and unfortunately the “solution” the grower chooses many times is not the right one. A mis-diagnosis only serves to make matters worse by promoting further decline. I’ll try to cover some of the more common causes that can induce these common symptoms and try to offer a few simple solutions. The ultimate and correct solution is in the hands of the grower.

1. Over-fertilizing - the most common cause of leaf cupping aka leaf margin rolling, leaf margin burn, and leaf tip curl/burn is the overzealous use of too much plant food in relationship to factors such as plant size, vigor and rate of growth. The first unit of a plant to show moisture stress is the leaf at its margins and/or tips, reflected by margin rolling (cupping) or burning. Sometimes copper colored necrotic spots show in the leaf also. A hard, crispy feel to the leaf frequently occurs as well, as opposed to a soft and cool feel of a happy leaf. When you have a high concentration of salts in solution (or in the root medium) compared to lower salinity levels found in the plant’s tissue, water is actually drawn out of the plant across the root gradient in order to fix the ppm imbalance. IOW, this is a natural, osmotic response that serves to equalize salinity levels on both sides of the root’s epidermal gradient. Back off on the amount and/or frequency of plant food. Too much plant food can also burn the roots, especially the sensitive root tips and hairs, which then creates another set of problems such as nutrient deficiencies. A note for the bio folks - as soil dries, the concentration of the remaining salts rises further exacerbating the problem. Leach (flush) your pots once in a while to get rid of excess salts.

2. High Heat - the plant is losing water via it’s leaves faster than what can be replaced by the root system. The leaf responds by leaf margin cupping or rolling (up or down) in order to conserve moisture. A good example is reflected by the appearance of broad-bladed turf grass on a hot summer day, high noon, with low soil moisture levels - the leaf blade will roll in and the grass will take on a dull, greyish-green appearance. Upon sunrise when moisture levels have returned to normal, the leaf blade will be flat. Lower the heat and concentrate on developing a large, robust root system by practicing sound plant culture. An efficient and effective root system will go a long way to prevent heat induced leaf dessication and leaf margin curling by supplying sufficient moisture for good plant health. One short episode of high heat is enough to permanently destroy leaf tissue and cause a general decline in the leaves affected, which often occurs to leaves found at the top of the plant located near HID lamps. The damaged leaf (usually) does not recover, no matter what you do. Bummer in the summer. One can only look to new growth for indications that the problem has been corrected.

3. High Light - yes, it’s true, you can give our faves too much light. Cannabis does not receive full sun from sunrise to sunset in its natural state. It is shaded or given reduced light levels because of adjacent plant material, cloudy conditions, rain, debris and dust collection on the leaf surface, twilight periods of early morning and late afternoon, and light intensity changes caused by a change in the seasons. Too much light mainly serves to bleach out and destroy chlorophyll as opposed to causing leaf cupping, but it often goes hand-in-hand with high heat for indoor growers. Again, back off on the light and concentrate on developing/maintaining an efficient and robust root system. Keep in mind that all but equatorial material receive less light during flowering than during the vegetative stage.

4. Overwatering - this practice only serves to weaken the root system by depriving the roots of proper gas exchange. IOW, the roots are not getting enough oxygen which creates an anerobic condition causing root decline and root rot with the end result showing up as leaf stress, stunted growth, and in severe cases, death. <gasp!> Alot of times folks think the plant is not getting enough plant food (which it can't under such adverse conditions), they add more nutes for a "curative", and just add insult to injury.

5. Underwatering - not only is the plant now stressed due to a low supply of adequate moisture, but carbohydrate production has been greatly compromised (screwed up). Step up the watering frequency, and if need be, organic growers may need to soak the pot from the bottom up until moisture levels reach an even consistency throughout the medium especially with mixes that are heavy in peat. If severe, a little surfactant (liquid Ivory dish soap) added to the drench will help return the organics back to a normal moisture retentive state. If the pot feels light to the lift - it&#8217;s time to water. Don&#8217;t wait until the soil pulls away from the sides of the pot or leaves droop before you water.

Happy gardening,
Uncle Ben

Please help i think I transplanted late and my humidity is only 30% will they come back around or should I bin them

I have bought a hr15 humidifier and it can only get Upto 42%
With my extraction turned down as much as possible temps in the room 27.5

Strain stardawg

20 days old from cutting
 

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SoCalCraw

Member
I've also got a problem of my own on my hands, I'm hoping someone can help me!!

I've got a 15 plant limit, no rules on how many in flower at a time just 15 total root systems and plan on putting them in a 16x7x7 shipping container that's insulated to withstand temps in the -30 to -40°C and am definitely taking notes on cleanliness.

I recently just purchased a 1000W HPS that Im using in a 2x4x7 closet that is running AC to the bottom of the Grow box (that's within the closet) and allowing to rise to the ceiling along with 2 CPU fans and a little area fan to circulate the air best as I can. Temp stays at about 26°C with a 30% RH with the lights on, with the lights off it stays at 20°C with a 50-55% RH.

Previous to putting an AC unit in the closet there was just the fans, exceeding temps of over 30°C and having a RH of close to 60% and I would say for a good day, causing enough heat stress to
slightly taco my lady's leaves, the blades are coming up but the leaves aren't necessarily 'cupping'.

My question is, is this cupping reversible if I'm able to keep the temps controlled at the current ~26°C/30% DAY vs. ~20°C/50% NIGHT? Is there any way to reverse cupping?

I've got one super auto NL that's about 3.5 feet tall (having to bend her over because the lights too intense) that's under the 1000W she's on her 8th week of life out of about "10-12". Buds are forming nicely but they have a bit of a damp smell to them. I've inspected every little bit between her and there is absolutely no sign of mold, just that wet towel smell. I'm a little lost there also but it must have something to do with the humidity. Some leaves also have some yellow spotting I'm assuming due to that one bad heat wave they endured when I first got my light.

I'm just trying to get dense, good smelling nugs because I have the power just not necessarily the skill, and that's why I'm reaching out to those who do!

Here's a picture to get a better sense of what I'm dealing with, unfortunately my set up is super ghetto at home since I'm spending literally all my money on insulating those shipping containers for the harsh Canadian winters so please bare I appreciate you all in helping out in the medical and recreational cannabis communities, especially for Canadians at least it's not easy to find this information freely available from someone with experience!!

PS: this is my first grow! Please shoot out any constructive criticism! Just please don't be too too mean :) thanks again!!
 

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Michiganjesse

Well-Known Member
I've also got a problem of my own on my hands, I'm hoping someone can help me!!

I've got a 15 plant limit, no rules on how many in flower at a time just 15 total root systems and plan on putting them in a 16x7x7 shipping container that's insulated to withstand temps in the -30 to -40°C and am definitely taking notes on cleanliness.

I recently just purchased a 1000W HPS that Im using in a 2x4x7 closet that is running AC to the bottom of the Grow box (that's within the closet) and allowing to rise to the ceiling along with 2 CPU fans and a little area fan to circulate the air best as I can. Temp stays at about 26°C with a 30% RH with the lights on, with the lights off it stays at 20°C with a 50-55% RH.

Previous to putting an AC unit in the closet there was just the fans, exceeding temps of over 30°C and having a RH of close to 60% and I would say for a good day, causing enough heat stress to
slightly taco my lady's leaves, the blades are coming up but the leaves aren't necessarily 'cupping'.

My question is, is this cupping reversible if I'm able to keep the temps controlled at the current ~26°C/30% DAY vs. ~20°C/50% NIGHT? Is there any way to reverse cupping?

I've got one super auto NL that's about 3.5 feet tall (having to bend her over because the lights too intense) that's under the 1000W she's on her 8th week of life out of about "10-12". Buds are forming nicely but they have a bit of a damp smell to them. I've inspected every little bit between her and there is absolutely no sign of mold, just that wet towel smell. I'm a little lost there also but it must have something to do with the humidity. Some leaves also have some yellow spotting I'm assuming due to that one bad heat wave they endured when I first got my light.

I'm just trying to get dense, good smelling nugs because I have the power just not necessarily the skill, and that's why I'm reaching out to those who do!

Here's a picture to get a better sense of what I'm dealing with, unfortunately my set up is super ghetto at home since I'm spending literally all my money on insulating those shipping containers for the harsh Canadian winters so please bare I appreciate you all in helping out in the medical and recreational cannabis communities, especially for Canadians at least it's not easy to find this information freely available from someone with experience!!

PS: this is my first grow! Please shoot out any constructive criticism! Just please don't be too too mean :) thanks again!!
First grow doing pretty good leaves may not come back doubtful. but they should be just fine to continue
 

SoCalCraw

Member
I have kept my temp between 70-80 degrees. I've been watering every 2-3 days. How much run off am I suppose to have when watering?
The runoff will all depend on your plants root systems and how much the dirt around them is soaking in and holding on to so it's hard for me to tell you the answer on that one.

A good test i like to do Is to measure the amount of water before I give it to a plant (if you're not worried about ph testing your runoff all the time), let's say 1.5L. Place the pot over a large bowl so there's room between the bottom of that plants pot and the bottom of the bowl for your runoff to go into. Make sure however your plant is decently dry, and pour that water on the plant, after it stops dripping lift the pot and take out the bowl, measure the water in your bowl, let's say .25L. (1.5-.25)That means your pot is able to retain 1.25L of water without runoff which is key to getting the farthest root tips water and not overwatering it by keeping the bottom constantly moist.

I hope that helps a bit and I hope your babies perked back up!!!!
 

SoCalCraw

Member
Update on my own heat stress question earlier:

70% of the leaves coming off the buds had some form of heat stress, either taco or edges lifting up, but the harvest was actually pretty good.

I got 2oz dry and cured from a Northern Lights Autoflower Feminized grown under 150W of T5 and then put in flower under a 1000W Agrolite with a fire retardant thin ass sheet to soften the strength of the light hitting the plants since it's in a closet (I got super lucky with that find, I don't suggest doing that unless you're absolutely desperate at the time, which I absolutely was) and in soil (miracle grow potting mix).

I want to let people know that these plants are very very very hardy, I can't repeat that enough. When I saw all of my leaves starting to taco I did immediate action (added AC unit, boxed in grow area for easier ventilation, stabilized temps between day and night, etc) since I was in a panic and I learnt from those experiences that much worse things could have happened. The plant won't die unless you stress it out with heat above 90° for HOURS. Don't let the taco's by your nugs push you down as they did to me, your plant still has plenty of other leaves down the branch to support the growth of buds on them that you might not think are enough but definitely will be (in terms of Autoflowers).

I can't say the same for non auto's since pruning and other techniques will probably (idk) make it so that if there is heat stress the plant won't have enough other leaves to rely on and I'm assuming as a result could have a higher chance of dying due To a heat wave even after you might have fixed the problem.
 

Ag3life

Member
The runoff will all depend on your plants root systems and how much the dirt around them is soaking in and holding on to so it's hard for me to tell you the answer on that one.

A good test i like to do Is to measure the amount of water before I give it to a plant (if you're not worried about ph testing your runoff all the time), let's say 1.5L. Place the pot over a large bowl so there's room between the bottom of that plants pot and the bottom of the bowl for your runoff to go into. Make sure however your plant is decently dry, and pour that water on the plant, after it stops dripping lift the pot and take out the bowl, measure the water in your bowl, let's say .25L. (1.5-.25)That means your pot is able to retain 1.25L of water without runoff which is key to getting the farthest root tips water and not overwatering it by keeping the bottom constantly moist.

I hope that helps a bit and I hope your babies perked back up!!!!
Thanks for that tip!!!!
 

BBbubblegum

Well-Known Member
Please help i think I transplanted late and my humidity is only 30% will they come back around or should I bin them

I have bought a hr15 humidifier and it can only get Upto 42%
With my extraction turned down as much as possible temps in the room 27.5

Strain stardawg

20 days old from cutting
Humidity is too low. Start spraying them twice a day
 

710revolution

Active Member
Heres an extreme overwatering caused by a bad mistake on my part. Been on vacation the past week since 3/23. I overcompensated on what i thought my plants would drink, and i ended up overwatering them. Rookie mistake, and ive been growing off and on for over ten years. Its been dry for the past month and a half. They were drinking a lot before i took off last week. So im like ill soak them. I ended up drowning the bitches. It sucks balls, but i should have watched the forecast closer to see there was going to be a mini monsoon hitting home during the same time i was going to be gone. Relative humidity is at 70 freaking percent, so naturally my girls were not drinking as much as usual. I only went off what ive been doing the past 10 weeks. Not reading my plants or their grow enviornment. This has been a rough grow as it is because,well, life. Only the one plant is questionable to be able to finish. However, im pushing it anyway, to finish the grow. The others i am confident will finish out. Got two unknown strains. Which are the two obviously bigger plants. The other two are trainwreck auto from crop king seeds. 2ft×2ftx4ft tent with cheap ass blurples. Ive been running them all 12/12 for 3 1/2 weeks, 24hr a day before that. Gives a good visual of what overwatering looks like. Wrecks shit.
 

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PLANT MOISTURE STRESS - symptoms and solutions (revised Jan. 12, 2009)

Quite often I hear groans from folks having leaf problems -> &#8220;Help, my leaves are cupping and the leaf edges are turning brown!&#8221;, or, &#8220;My plant's leaf tips are curling down and turning black ....what's wrong?&#8221; Unless insect damage has occurred or the plant is suffering from a severe case of calcium deficiency, the plant is trying to tell you that it is water stressed. It's hard to tell *exactly* what the culprit is, and unfortunately the &#8220;solution&#8221; the grower chooses many times is not the right one. A mis-diagnosis only serves to make matters worse by promoting further decline. I&#8217;ll try to cover some of the more common causes that can induce these common symptoms and try to offer a few simple solutions. The ultimate and correct solution is in the hands of the grower.

1. Over-fertilizing - the most common cause of leaf cupping aka leaf margin rolling, leaf margin burn, and leaf tip curl/burn is the overzealous use of too much plant food in relationship to factors such as plant size, vigor and rate of growth. The first unit of a plant to show moisture stress is the leaf at its margins and/or tips, reflected by margin rolling (cupping) or burning. Sometimes copper colored necrotic spots show in the leaf also. A hard, crispy feel to the leaf frequently occurs as well, as opposed to a soft and cool feel of a happy leaf. When you have a high concentration of salts in solution (or in the root medium) compared to lower salinity levels found in the plant&#8217;s tissue, water is actually drawn out of the plant across the root gradient in order to fix the ppm imbalance. IOW, this is a natural, osmotic response that serves to equalize salinity levels on both sides of the root&#8217;s epidermal gradient. Back off on the amount and/or frequency of plant food. Too much plant food can also burn the roots, especially the sensitive root tips and hairs, which then creates another set of problems such as nutrient deficiencies. A note for the bio folks - as soil dries, the concentration of the remaining salts rises further exacerbating the problem. Leach (flush) your pots once in a while to get rid of excess salts.

2. High Heat - the plant is losing water via it&#8217;s leaves faster than what can be replaced by the root system. The leaf responds by leaf margin cupping or rolling (up or down) in order to conserve moisture. A good example is reflected by the appearance of broad-bladed turf grass on a hot summer day, high noon, with low soil moisture levels - the leaf blade will roll in and the grass will take on a dull, greyish-green appearance. Upon sunrise when moisture levels have returned to normal, the leaf blade will be flat. Lower the heat and concentrate on developing a large, robust root system by practicing sound plant culture. An efficient and effective root system will go a long way to prevent heat induced leaf dessication and leaf margin curling by supplying sufficient moisture for good plant health. One short episode of high heat is enough to permanently destroy leaf tissue and cause a general decline in the leaves affected, which often occurs to leaves found at the top of the plant located near HID lamps. The damaged leaf (usually) does not recover, no matter what you do. Bummer in the summer. One can only look to new growth for indications that the problem has been corrected.

3. High Light - yes, it&#8217;s true, you can give our faves too much light. Cannabis does not receive full sun from sunrise to sunset in its natural state. It is shaded or given reduced light levels because of adjacent plant material, cloudy conditions, rain, debris and dust collection on the leaf surface, twilight periods of early morning and late afternoon, and light intensity changes caused by a change in the seasons. Too much light mainly serves to bleach out and destroy chlorophyll as opposed to causing leaf cupping, but it often goes hand-in-hand with high heat for indoor growers. Again, back off on the light and concentrate on developing/maintaining an efficient and robust root system. Keep in mind that all but equatorial material receive less light during flowering than during the vegetative stage.

4. Overwatering - this practice only serves to weaken the root system by depriving the roots of proper gas exchange. IOW, the roots are not getting enough oxygen which creates an anerobic condition causing root decline and root rot with the end result showing up as leaf stress, stunted growth, and in severe cases, death. <gasp!> Alot of times folks think the plant is not getting enough plant food (which it can't under such adverse conditions), they add more nutes for a "curative", and just add insult to injury.

5. Underwatering - not only is the plant now stressed due to a low supply of adequate moisture, but carbohydrate production has been greatly compromised (screwed up). Step up the watering frequency, and if need be, organic growers may need to soak the pot from the bottom up until moisture levels reach an even consistency throughout the medium especially with mixes that are heavy in peat. If severe, a little surfactant (liquid Ivory dish soap) added to the drench will help return the organics back to a normal moisture retentive state. If the pot feels light to the lift - it&#8217;s time to water. Don&#8217;t wait until the soil pulls away from the sides of the pot or leaves droop before you water.

Happy gardening,
Uncle Ben
Great article Ben. I am attempting my third indoor closet grow, i really screwed up the first two grows somehow. i used to much or to little light, Over fertilizing, over watering and or to much heat from lights now that is said, how would i know which stage to give the plant nutrients and how much light to use if only growing one or two plants? Why do some growers use calmag or molasses etc. I hope I didn't hit you with too many questions but seems like a lot of people have different theories on indoor growing.
Thxs Moose
 

jbcCT

Well-Known Member
PLANT MOISTURE STRESS - symptoms and solutions (revised Jan. 12, 2009)

Quite often I hear groans from folks having leaf problems -> &#8220;Help, my leaves are cupping and the leaf edges are turning brown!&#8221;, or, &#8220;My plant's leaf tips are curling down and turning black ....what's wrong?&#8221; Unless insect damage has occurred or the plant is suffering from a severe case of calcium deficiency, the plant is trying to tell you that it is water stressed. It's hard to tell *exactly* what the culprit is, and unfortunately the &#8220;solution&#8221; the grower chooses many times is not the right one. A mis-diagnosis only serves to make matters worse by promoting further decline. I&#8217;ll try to cover some of the more common causes that can induce these common symptoms and try to offer a few simple solutions. The ultimate and correct solution is in the hands of the grower.

1. Over-fertilizing - the most common cause of leaf cupping aka leaf margin rolling, leaf margin burn, and leaf tip curl/burn is the overzealous use of too much plant food in relationship to factors such as plant size, vigor and rate of growth. The first unit of a plant to show moisture stress is the leaf at its margins and/or tips, reflected by margin rolling (cupping) or burning. Sometimes copper colored necrotic spots show in the leaf also. A hard, crispy feel to the leaf frequently occurs as well, as opposed to a soft and cool feel of a happy leaf. When you have a high concentration of salts in solution (or in the root medium) compared to lower salinity levels found in the plant&#8217;s tissue, water is actually drawn out of the plant across the root gradient in order to fix the ppm imbalance. IOW, this is a natural, osmotic response that serves to equalize salinity levels on both sides of the root&#8217;s epidermal gradient. Back off on the amount and/or frequency of plant food. Too much plant food can also burn the roots, especially the sensitive root tips and hairs, which then creates another set of problems such as nutrient deficiencies. A note for the bio folks - as soil dries, the concentration of the remaining salts rises further exacerbating the problem. Leach (flush) your pots once in a while to get rid of excess salts.

2. High Heat - the plant is losing water via it&#8217;s leaves faster than what can be replaced by the root system. The leaf responds by leaf margin cupping or rolling (up or down) in order to conserve moisture. A good example is reflected by the appearance of broad-bladed turf grass on a hot summer day, high noon, with low soil moisture levels - the leaf blade will roll in and the grass will take on a dull, greyish-green appearance. Upon sunrise when moisture levels have returned to normal, the leaf blade will be flat. Lower the heat and concentrate on developing a large, robust root system by practicing sound plant culture. An efficient and effective root system will go a long way to prevent heat induced leaf dessication and leaf margin curling by supplying sufficient moisture for good plant health. One short episode of high heat is enough to permanently destroy leaf tissue and cause a general decline in the leaves affected, which often occurs to leaves found at the top of the plant located near HID lamps. The damaged leaf (usually) does not recover, no matter what you do. Bummer in the summer. One can only look to new growth for indications that the problem has been corrected.

3. High Light - yes, it&#8217;s true, you can give our faves too much light. Cannabis does not receive full sun from sunrise to sunset in its natural state. It is shaded or given reduced light levels because of adjacent plant material, cloudy conditions, rain, debris and dust collection on the leaf surface, twilight periods of early morning and late afternoon, and light intensity changes caused by a change in the seasons. Too much light mainly serves to bleach out and destroy chlorophyll as opposed to causing leaf cupping, but it often goes hand-in-hand with high heat for indoor growers. Again, back off on the light and concentrate on developing/maintaining an efficient and robust root system. Keep in mind that all but equatorial material receive less light during flowering than during the vegetative stage.

4. Overwatering - this practice only serves to weaken the root system by depriving the roots of proper gas exchange. IOW, the roots are not getting enough oxygen which creates an anerobic condition causing root decline and root rot with the end result showing up as leaf stress, stunted growth, and in severe cases, death. <gasp!> Alot of times folks think the plant is not getting enough plant food (which it can't under such adverse conditions), they add more nutes for a "curative", and just add insult to injury.

5. Underwatering - not only is the plant now stressed due to a low supply of adequate moisture, but carbohydrate production has been greatly compromised (screwed up). Step up the watering frequency, and if need be, organic growers may need to soak the pot from the bottom up until moisture levels reach an even consistency throughout the medium especially with mixes that are heavy in peat. If severe, a little surfactant (liquid Ivory dish soap) added to the drench will help return the organics back to a normal moisture retentive state. If the pot feels light to the lift - it&#8217;s time to water. Don&#8217;t wait until the soil pulls away from the sides of the pot or leaves droop before you water.

Happy gardening,
Uncle Ben
I'm very liberal with my watering. Recently fed a few girls, then had rain, very moist for two days straight. Had some cupping last night. One bright sunny day today, mid 70's nice sun, cured cupping.

I'm a less is more guy when it comes to water & nutrients. I've always found my outdoor crops thrive on the dry side. I'm a firm believer most strains like it dry.
 

itsmeifti

Well-Known Member
Hi, can an expert let me know what is the problem with these? White spots on lower leaves - eventually 'crisp' and 'burn off'

3 x OG Kush, planted 7 may 17
All in one soil/nute mix ( 4 months release)
Context - been very wet over the last 2/3 weeks
Have tried onion/garlic puree on leaves last few days as a pesticide?
Advice welcome! IMG_20170607_143814.jpg IMG_20170607_143823.jpg IMG_20170607_143832.jpg IMG_20170607_143841.jpg
 
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