Plant Moisture Stress - Symptoms and Solutions

Discussion in 'Marijuana Plant Problems' started by Uncle Ben, Jan 12, 2009.

  1.  
    Uncle Ben

    Uncle Ben Well-Known Member

    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
  2.  
    GoldenGraham84

    GoldenGraham84 Active Member

    you should mention something about leaf curling/cupping due to the plant being rootbound.
  3.  
    Uncle Ben

    Uncle Ben Well-Known Member

    Thanks Dirtfree.

    Potbound plants usually exhibit signs of slowing growth, stunting, as opposed to moisture stress which is expressed via leaf cupping.

    I bet I could take 50% of the groans of the last couple of pages here and attribute some or most of the problems to moisture stress or improper watering issues.

    Uncle Ben
  4.  
    OneHit

    OneHit Well-Known Member

    What signs to plant exhibit if they are in a low humidity environment? My plants RH is 16-20% And I read thats way too low
    RyanTrees likes this.
  5.  
    Uncle Ben

    Uncle Ben Well-Known Member

    No two gardens are the same, forget what you read and learn to read your plants.

    If you have a robust, effective root system, a RH of 20% is fine, all other factors considered. In fact, that kind of RH during latent flowering with indica doms is a blessing regarding possible bud rot or fungus issues.

    Good luck,
    UB
  6.  
    OneHit

    OneHit Well-Known Member

    How do I tell if it has a robust effective rootsystem?
  7.  
    tryinghard

    tryinghard Active Member

    great thread UNC,,, my pal Pete from CH9 was telling me the samething i was overfertin my plants,,every problem i was having u just described to a tee,,, you really know your shit,,, this will help a lot of people,,,peace
    RyanTrees likes this.
  8.  
    canadiancracker

    canadiancracker Active Member

    can you help check these out

    thanks in advance,

    i think it might be over watering or maybe too much light.

    thanks in advance, great thread by the way...
  9.  
    Uncle Ben

    Uncle Ben Well-Known Member

    You'll have abundant foliage and the pot will need watering often. The condition and mass of the foliage pretty much indicates the same with the root system.

    tryinghard, thanks bro. It's helped out alot of people over the years. It's pretty basic stuff but sometimes we lose sight of the forest for the trees.

    UB
    czogbe and NotoriousBUD like this.
  10.  
    Uncle Ben

    Uncle Ben Well-Known Member

    You'll have abundant foliage, a very healthy looking plant and the pot will need watering often. The condition and mass of the foliage pretty much indicates the same regarding the root system's condition.

    tryinghard, thanks bro. It's helped out alot of people over the years. It's pretty basic stuff but sometimes we lose sight of the forest for the trees.

    UB
    Theanswerto1984is1776 likes this.
  11.  
    Uncle Ben

    Uncle Ben Well-Known Member

    [​IMG]

    I don't see any symptoms of too much light. Me? I keep my leaves alot greener than that VVV but your light medium green leaves aren't really a problem. Not now anyway. Problems start when folks hit them during flowering with N deficient (high P) foods.

    [​IMG]

    Water when the pot feels light to the lift, but before it starts showing moisture stress (droopy leaves).

    What's the makeup of your mix, soil and hydroton on top? Why the hydroton and what kind of soil are you using? What's its structure like, open or tight?

    UB

    Attached Files:

  12.  
    tryinghard

    tryinghard Active Member

    hey UNC i gotta give credit where credits due,,,, and like u said its helped many people over the years i am sure, and 3 years from now it will still be helping thx 2 people like you,,, hell sometimes it feels like i completely left the forest let alone lose sight of it,,,peace
  13.  
    Uncle Ben

    Uncle Ben Well-Known Member

    Yeah, it's all about botany and using common sense. It's when you stray from the common sense part of growing this weed that things can (and will) go south on ya. :weed:

    Thanks for the kind words. I've got something up my sleeve regarding putting together 40 years of tweeks learned at the School of Hard Knocks. Stay tuned. :D

    Tio Bendejo
    communistcannabis and TKronic like this.
  14.  
    OneHit

    OneHit Well-Known Member

    UB, What do you think is wrong with this plant? I had sprayed neem oil the day before, and after I woke up and the lights turn on, they were like this. I thought it would go away in a day, buit it didnt.

    Attached Files:

  15.  
    canadiancracker

    canadiancracker Active Member

    my soil is made up of 1/6 vercumilite, and 5/6 potting soil, kinda tight soil. i also mixed in the hydroton into the mix before filling my pots for extra air in the soil. the hydroton on top is to help keep some moisture in the soil. last crop i used the same pots and plants vegged for the same amount of time and the lights were baking the promix hp and drying it out too quick.

    my grow before the last one i used dr scultz pro potting soil with time release ferts and my plants turned out amazing so i tryed to make a simular soil for this grow except i mixxed it myself to save some money, which i dont think ill ever do again,, promix hp it is for me....

    thanks
  16.  
    Uncle Ben

    Uncle Ben Well-Known Member

    It appears that the neem oil product burned them (drew moisture out of the leaf tissue), most likely the carrier was the culprit. Safer Soaps are notorious for doing that, reason why I won't use 'em. The damage has been done, and most likely those leaves will not recover. Might have to put it behind you and focus on the condition of the new growth only. You could always blast them with some distilled or rain water and see if that helps.

    canadiancracker, using hydroton to open up a soil is like dropping a handful of marbles in a big bag of flour. Use vermiculite and perlite to open up your soils and save your money regarding the hydroton. Or if you're skittish about overwatering, use a 1" layer of the hydroton in the bottom of the pot.

    I am a commercial grower (farmer of niche crops) and use a slow release fertilizer on everything, we're talkin' thousands of plant material. It's an excellent way to provide plants with what they really like, a slow release source of food on a continuous basis. If those encapsulated granules were green, then you have a Polyon, a Harrell plant food product which I buy in 50 lb. bags. I believe that is what Schultz uses. DO mix your own custom soil, just add some slow release foods like blood and bone meal and Osmocote or any other encapsulated slow release food.

    Good luck,
    UB
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  17.  
    yobdub

    yobdub Active Member

    great advice im stressing over plants(1st GROW) some info seems to contradict other pros that are trying to help but from my experiance your info seems more logical.....maybe logic doesnt produce more bigger buds I have been over waterig/fertin and when i chill and be patient things look better Lord im an impatient bastard especially when im smokin schwag and waitin for my grow to finish :weed: GOD BLESS RIU PEOPLE
  18.  
    Uncle Ben

    Uncle Ben Well-Known Member

    That's a natural newbie response, you're apprehensive and fear of the unknown will getcha by the cajones every time. Just keep it simple and grow your plants like you would tomatoes. Remember, pot is a weed and where folks screw it up is by overdoing things.

    Less is more.

    My info is based on many years of experience and botany. I don't subscribe to most of the cannabis forum paradigms, snake oils and rocket fuels.....there's too much voodoo majic in this biz and it doesn't have to be that way. If folks would stop glamorizing and romanicizing weed and stop treating it with some wacked out air of mystique, they would have better results. Just grow the frickin' weed and be done with it. :D

    Not to toot my horn, but I'm known for producing only big, chunky colas...when it comes to hybrids. Sativas are a different matter and tend to be airy, fluffy type buds but I do well with those indoors too such as old Mex, Zamal, O. Haze, etc. Here's a link which reveals not only typical nugs I grow but the speed and vigor you'll see in my gardens. Check out the health and color on one of my crosses, a male that I destroyed. That's the kind of plant health and color you should aim for. http://www.drugs-forum.com/growfaq/1321.htm

    Like I said, "less is more". Learn to read your plants, they will tell you when it's time to water, when they need more or LESS light, etc. It's a balancing act regarding all of the cultural variables and factors.

    Good luck,
    UB
    TwistedGenetics likes this.
  19.  
    OneHit

    OneHit Well-Known Member

    UB, I just checked out that link. Do you recommend using that spinout spray? Also, do you have any personal experience with feminized seeds? Im growing one, and there have been some light cycle moments when the timer wasnt working properly, as well as some potential light leaks coming from my mothering chamber, and I hear all these horror stories about feminized seeds turning hermie. WHen they DO go hermie, is it the entire plant? Or one branch? Ive also taken some clones from this mother. Do I need to toss them immediatly if I find that the mother has turned hermie?
  20.  
    Kriegs

    Kriegs Well-Known Member

    Thanks, UB, for this awesome post and the thread that follows. Less really is more... I'm in my first grow, but I've been gardening avidly for 15 years. When I started growing weed, I tossed out everything I knew for "the mystique and voodoo" you mention. Well, just for a couple weeks -- I quickly pulled my head out, shook off the fog and said "it's just a damn plant, man!", and my plants are kickin' ass now. They're starting to freak me out with how much space they're filling.

    Just a couple little things to add:

    1) People either don't know or forget that plants are water pumps. So, the bigger/smaller the plant the more/less water you need. Therefore, the watering regime you had a week ago no longer works with a fast-growing plant like MJ. I've gone from 8-10 day watering intervals at seedling stage to barely keeping up at 4 weeks old with every-other-day waterings. They just suck it up.

    2) Newbies: Get a moisture meter. They're 5 lousy bucks at Lowe's, etc. Once you have it and know how to use it, don't argue with what it says. I find mine really helpful 'cause under a 18 hours of beaming HPS light and fanning, that top inch of soil is going to be dry within hours of watering while you may have a root-killing swamp developing down below (thus confounding the "place a finger an inch into the soil" measure). The meter probe lets you see what's going on throughout the pot top to bottom. I'm sure the meter becomes obsolete with experience, but for newbies, I think it's a great way to get solid on your watering approach.

    Thanks again, UB!

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