Plant Moisture Stress - Symptoms and Solutions

Michiganjesse said:

Just through a strawberry banana into flower last week going to run her dry in this system and see what it does. Cross my fingers

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Uncle Ben said:

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

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chuckie86 said:

Can anyone help not sure whats going on with my plants

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Ag3life said:

HELP!!!!! She looked good just a few hours ago.

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SoCalCraw said:

What are your temps like? And how much water/ how often?

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SoCalCraw said:

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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Ag3life said:

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?

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Ag3life said:

HELP!!!!! She looked good just a few hours ago.

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SoCalCraw said:

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!!!!

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chuckie86 said:

Yea buddy they just need some water

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danzibar1234 said:

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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Uncle Ben said:

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

Click to expand...

Uncle Ben said:

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

Click to expand...