Plant Moisture Stress - Symptoms and Solutions

GrowingfortheGold said:

in other words...

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W Dragon said:

thankyou mate much appreciated i'm not very good when it comes to abreviations rep for the help and not taking the piss, it was driving me nuts

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Uncle Ben said:

See page 69 & 70.



UB

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hangshai said:

Ive turned it off for now, and they have definitely bounced back, but, now Im wondering how early in veg can you turn on co2? Can you do it as soon as your clones are rooted, or should you at least wait until the plant is 10-12 inches tall?

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mr.smileyface said:

Your flo? or chunk

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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’s time to water. Don’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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Uncle Ben said:

FWIW - for what it's worth
AKA - also known as
FYI - for your information
BTW - by the way

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W Dragon said:

thanks mate that'll save me looking like a dimb arse in future lol i'm still adjusting to using the pc. i'll be sending rep over aswell when it lets me, for the most part i only read yours and riddleme's threads i was wondering if you know of any other educational threads like yours that would benefit a noob like myself, oh yeah i'll be ordering mel franks book next week thanks mate

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Uncle Ben said:

Frank offers solid, simple info which is what you need. There's plenty of info on the web about plant culture. Aside from guys like Mel Frank's hard copy, I'd stay away from cannabis forums or at least take them with a grain of salt. There's too much confusion and hype and that's not what you need to succeed. Anyone can flip a timer, not many will take the time to understand what makes a plant tick.

Here's another site that dispels alot of horticultural myths, a must read at this link: http://www.puyallup.wsu.edu/~Linda Chalker-Scott/

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SIRE said:

uncle ben...... i've been doing well on the grow side since ive talk to u dave and other cats on here thank all of u. now i've been on a few other forums and i came across a few things. i no u said u dont use nutes specified for mari but i still wanted to enlist ur expertise. i have biobizz products (bio grow, fishmix,) i just bought some cal-mag, and superthrive (which is already added in my gallon of distilled water) now can i mix the bio grow fish and cal-mag together in one spray?

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Uncle Ben said:

I never bothered with CO2 injection, but I don't see why you couldn't use it at any time.



No, the Griffin's Spin-Out experiment.

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Uncle Ben said:

Spray? Don't know, try it and see.

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SIRE said:

uncle ben...... i've been doing well on the grow side since ive talk to u dave and other cats on here thank all of u. now i've been on a few other forums and i came across a few things. i no u said u dont use nutes specified for mari but i still wanted to enlist ur expertise. i have biobizz products (bio grow, fishmix,) i just bought some cal-mag, and superthrive (which is already added in my gallon of distilled water) now can i mix the bio grow fish and cal-mag together in one spray?

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dakin3d said:

Last, do you use CO2? Is it a bad thing to use CO2 in an environment that will receive very little 'new air', due to lack of ventilation?

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Uncle Ben said:

Keep the fans on constantly.



UB

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