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Dark Time Temps ?
- Thread starter Swan Lee
- Start date
From what I've heard (and there is no actual research behind this other than reading these forums LOTS) the temp isn't so important, just that you want the variance of temp between day/night to be 5-10 degrees. So if you're running 80 degrees day, try to run 70-75 night, etc. My current grow varies more than that, but I'm working on dialing it in more and more. If I'm wrong, anyone please feel free to correct me.
G
greendream420
Hey mate, i bookmarked this a little while ago.
You may find it interesting, it's an old article from cannabis culture magazine.
I pinched it from this site here
https://www.*********.com/community/threads/what-makes-dense-buds.39252/
Control your cannabis
By DMT, photos by Barge - Monday, April 24 2000
Fine-tuning temperature and water for maximum quantity and quality.
Why waste light and electricity growing stem? Stretched-out plants are the bane of indoor growers. There are several ways to reduce internodal length and thus grow denser, more efficient buds.
Temperature control
The easiest and most under-used way to control internodal stretch is temperature control. Plant internodal length is directly related to the difference between day and night temperatures ? the warmer your day cycle is as compared to your night cycle, the greater your internode length will be. The opposite also holds true; the closer your day and night temperatures, the shorter your internodes will be. Ever notice how as the warmer summer months approach, your plants begin to stretch? Part of this problem may lie in an overall hotter grow-room, but a larger factor is the increased difference between day and night temperatures.
Lets look at putting this to play in your grow room. Maximum temperatures should ideally never rise above 26?C, so you must do everything you can to prevent your room getting too hot (run lights at night, use exhaust fans, air conditioners, etc). An ideal temperature range is 24-25?C when the lights are on, and 22?C when the lights are off.
The temperature technique is most effective under a 12/12 light regime, which is ideal as this is when cannabis stretches the most. When the light cycle is brought to 12/12 we will raise the night temperature to the daytime level of 24-25?C. Space heaters on timers work well for this, and max/min type thermometers are ideal
It is during the first 2-3 weeks of the flower cycle that most strains begin to lengthen internodes, making it a very important time to control temperature, as this is when the framework for future colas is built. After this 2-3 week window we need to drop the night temperature back down to 22?C, as this is where the plant is happiest.
As floral development begins we need to keep in mind that the total size of your buds is determined largely by average daily temperature, provided it does not exceed optimal. So if you are letting your day temperatures drop below 24?C or your night drop below 22?C, you are costing yourself in overall weight and harvest.
Once your buds have reached optimal size and and you have begun the flushing period, you may consider dropping temperature down to 17-19?C for the final week or two. This drop in temperature triggers anthocyanin production, which intensifies the colour of the floral clusters and makes for a showier bud, especially with "purple" varieties. This final temperature change is not always feasible and can be omitted.
For extreme height control you may even use warmer night temperature than day, but be very careful when running settings like this, as even a zero difference between night and day temperatures will lead to leaf chlorosis (yellowing) after 2-3 weeks.
Some things you will notice while using this technique are a change in the leaf angle, upwards during warm days and downwards during warm nights. There is also the chlorosis if this is done for too long. Neither of these symptoms is nutrient related and will fix themselves when the temperature is changed back.
Moisture and conductivity
Whether you're growing hydro or in soil, the electrical conductivity (EC) and moisture of your medium are two key elements that should be manipulated to meet your needs. Both of these factors are controlling the same thing; the ability of a plant to uptake water and nutrients from the growth medium. (EC measures the level of fertilizer salts in the water.)
A plant grows by first dividing cells then expanding them, and in order to do this it requires water. By limiting the amount of water available to a plant you limit the expansion of cells. This can work for you by keeping your internodes close together, or against you by limiting bud growth. Both the amount of water you give your plants and the EC at which you grow them control the uptake of water.
A plant's roots act much like a pump, using osmotic pressure to move water into the plant. In order for this to work there must be a larger concentration of fertilizer salts in the plant's roots than in the soil or hydroponic solution, so when the medium's level of salt rises above the roots', the plant will wilt. Raising the salt level in the medium closer to that which is in the roots limits the water availability just the same as if we had provided less water.
During the vegetative stage we want our plants to form very tight internodes, especially under artificial lighting. By allowing the EC to drop below ideal during this stage we are wasting valuable space growing stem instead of bud. Most marijuana strains are happiest when grown at an EC of between 1.5 and 1.8, but different strains have different preferences. Try growing one of your plants using straight water for a week or so, you will see the internode length stretch dramatically compared to the ones on a regular fertilizer regime.
Hydroponic tomato growers sometimes will grow their transplants at extremely high EC's (up to 6 EC!) in order to get really nice stocky production plants. Please note that when doing this they use special nutrient formulas designed for this purpose, most of which have potassium to nitrogen ratios of 4:1, much higher than normal, as too much nitrate at this high an EC will easily damage a plant.
(Try this formula if you're interested: calcium nitrate 7 grams, potassium nitrate 0.095 grams, potassium sulphate 9.25 grams, mono potassium phosphate 2.2 gram, magnesium sulphate 5 grams, micromix .02 grams. Slowly raise your EC during veg stage, I would not recommend going above 3 or 4 EC. This is experimental! Do not try on all of your plants at once until you are sure your strain can handle it. All of these ingredients should be available at your local hydroponics store, it is usually called "six pack formula". Be sure to bring your EC back down once you enter floral stage, by the time tufts of pistils are visible you want to be at your ideal EC of 1.5-1.8.)
Try not to change the EC too quickly as a sharp drop can cause root damage. This also goes during your final flushing period when you want to eliminate all fertilizer from the medium ? lower the EC over a couple of days, as the sudden change in salt level will harm the roots.
When growing hydroponically, the only way of manipulating water availability is with the EC, while in soil we may also use the moisture level of the medium to the same ends. Many growers are under the mistaken impression that the EC and pH of their nutrient solution remains the same when applied to the soil. This in not the case, and you must test the soil in order to have a true
picture.
To test your soil, take a sample from the center of the root zone at the side of the pot (don't worry the torn roots will be fine). Mix the soil with 2 equal parts distilled water and let sit for 20 minutes. Once the time is up take an EC reading and multiply this number by 2.4 (this takes into account the dilution and the pore space factor) this will give you an accurate picture of the EC the roots are actually being exposed to. The pH should also be checked at this time. It is not feasible in soil to maintain an exact EC at all times, what we need to try and avoid is EC's climbing much above what we want and plants going for long periods with very low EC's.
A frequent mistake marijuana growers make is over-emphasizing the need for a plant grown in soil to dry out completely between waterings. Cannabis does like dry feet but this simply means that the root zone must not be kept extremely wet at all times. Keep in mind that if the soil has an EC of 1.8 and then dries out completely the amount of salt remains the same, causing the EC to double or more.
As a general rule, during the vegetative stage you should keep your plants a little on the drier side as this will restrict cell elongation, creating a shorter noded plant structure capable of creating a dense bud cluster in the floral stage. (Unless of course you are using the high EC method described above, in this case you must not let your soil get too dry because of the increased fertilizer level you will create.) Maintain this level of moisture into the first 14 to 20 days of 12/12 to minimize internode stretch.
As soon as early flowering begins you need to increase soil moisture to a nice evenly moist (not soaked) level to maximize bud expansion. Growing marijuana too dry during this stage will adversely affect your overall yield, as will having too high an EC in the medium.
tight internodes
example of tight internodes(closeup)
long internodes
example of long internodes (closeup)
leaf chlorosis (yellowing)
http://www.cannabisculture.com/v2/articles/1536.html
Also, big healthy green leaves are crucial to making big dense buds.
1. Never remove a leaf from the plant, unless the leaf is already about to fall off on it's own due to over-maturity(or accidental/premature death). Pruning shade leaves to increase light reaching lower buds is not a wise choice. You will never make up for the loss of production to the top of the plant from whatever may be gained on the lower part. The answer to that is to provide sufficient lighting to the lower buds, optimal reflectivity is the best way to get more light to the lower parts of the plant. Or just remove them from the plant(why you would is another argument really, so I won't be addressing it here, but I don't recommend it either). Light loses intensity/strength based on distance from the source. So you gain relatively little from doing anything except moving the source closer to the plant, or vise versa. Leaves serve a very important purpose in maintaining plant health and vigor. Buds are not going to efficiently feed themselves without them. LEAVES ARE BUD FEEDERS, NOT BUD FOOD!
2. Never flush. Pre-harvest flushing is such a fat dense bud killer it's not even funny. Just in the hopes of getting a better flavored smoking material. Which you won't. It may actually worsen the flavor, density, smokability, and/or potency of the buds. MINIMALLY you will lose harvested/dried weight. You're essentially starving the plant to death. When you should be feeding it what it needs to grow the BIGGEST DENSEST buds at the point in it's life cycle when that's exactly what it wants to do. Yes, I know the article mentions it, but I don't see that as a recommendation. Just how to incorporate the method, if desired. Which you should desire not, trust me. Much foolishness. Mother Nature, the best grower in the universe, doesn't flush her plants, and nor should you. AND IT WILL ACTUALLY INCREASE INTERNODE LENGTH/STRETCH, GUARANTEED!!!
Lastly, stems. Bigger, denser, heavier buds also need bigger thicker stems to pipe in all the nutritional building blocks used to make them, and to help support their weight. While controlling internode length is very effective at improving density, providing a simulated breeze of adequate strength is THE ONLY non-nutritional way to build a larger-diameter/sturdier stem structure. When the plant grows to resist the forces of wind it will naturally respond to it by thickening it's stems/branches. This benefits the buds come flowering time by allowing them to grow much larger and/or faster. In this sense you can force the plant to grow as if it were older, taller, and/or heavier than it really is. You also will have less need to support the plant by manual methods(stakes, strings, cages, etc.)
You may find it interesting, it's an old article from cannabis culture magazine.
I pinched it from this site here
https://www.*********.com/community/threads/what-makes-dense-buds.39252/
Control your cannabis
By DMT, photos by Barge - Monday, April 24 2000
Fine-tuning temperature and water for maximum quantity and quality.
Why waste light and electricity growing stem? Stretched-out plants are the bane of indoor growers. There are several ways to reduce internodal length and thus grow denser, more efficient buds.
Temperature control
The easiest and most under-used way to control internodal stretch is temperature control. Plant internodal length is directly related to the difference between day and night temperatures ? the warmer your day cycle is as compared to your night cycle, the greater your internode length will be. The opposite also holds true; the closer your day and night temperatures, the shorter your internodes will be. Ever notice how as the warmer summer months approach, your plants begin to stretch? Part of this problem may lie in an overall hotter grow-room, but a larger factor is the increased difference between day and night temperatures.
Lets look at putting this to play in your grow room. Maximum temperatures should ideally never rise above 26?C, so you must do everything you can to prevent your room getting too hot (run lights at night, use exhaust fans, air conditioners, etc). An ideal temperature range is 24-25?C when the lights are on, and 22?C when the lights are off.
The temperature technique is most effective under a 12/12 light regime, which is ideal as this is when cannabis stretches the most. When the light cycle is brought to 12/12 we will raise the night temperature to the daytime level of 24-25?C. Space heaters on timers work well for this, and max/min type thermometers are ideal
It is during the first 2-3 weeks of the flower cycle that most strains begin to lengthen internodes, making it a very important time to control temperature, as this is when the framework for future colas is built. After this 2-3 week window we need to drop the night temperature back down to 22?C, as this is where the plant is happiest.
As floral development begins we need to keep in mind that the total size of your buds is determined largely by average daily temperature, provided it does not exceed optimal. So if you are letting your day temperatures drop below 24?C or your night drop below 22?C, you are costing yourself in overall weight and harvest.
Once your buds have reached optimal size and and you have begun the flushing period, you may consider dropping temperature down to 17-19?C for the final week or two. This drop in temperature triggers anthocyanin production, which intensifies the colour of the floral clusters and makes for a showier bud, especially with "purple" varieties. This final temperature change is not always feasible and can be omitted.
For extreme height control you may even use warmer night temperature than day, but be very careful when running settings like this, as even a zero difference between night and day temperatures will lead to leaf chlorosis (yellowing) after 2-3 weeks.
Some things you will notice while using this technique are a change in the leaf angle, upwards during warm days and downwards during warm nights. There is also the chlorosis if this is done for too long. Neither of these symptoms is nutrient related and will fix themselves when the temperature is changed back.
Moisture and conductivity
Whether you're growing hydro or in soil, the electrical conductivity (EC) and moisture of your medium are two key elements that should be manipulated to meet your needs. Both of these factors are controlling the same thing; the ability of a plant to uptake water and nutrients from the growth medium. (EC measures the level of fertilizer salts in the water.)
A plant grows by first dividing cells then expanding them, and in order to do this it requires water. By limiting the amount of water available to a plant you limit the expansion of cells. This can work for you by keeping your internodes close together, or against you by limiting bud growth. Both the amount of water you give your plants and the EC at which you grow them control the uptake of water.
A plant's roots act much like a pump, using osmotic pressure to move water into the plant. In order for this to work there must be a larger concentration of fertilizer salts in the plant's roots than in the soil or hydroponic solution, so when the medium's level of salt rises above the roots', the plant will wilt. Raising the salt level in the medium closer to that which is in the roots limits the water availability just the same as if we had provided less water.
During the vegetative stage we want our plants to form very tight internodes, especially under artificial lighting. By allowing the EC to drop below ideal during this stage we are wasting valuable space growing stem instead of bud. Most marijuana strains are happiest when grown at an EC of between 1.5 and 1.8, but different strains have different preferences. Try growing one of your plants using straight water for a week or so, you will see the internode length stretch dramatically compared to the ones on a regular fertilizer regime.
Hydroponic tomato growers sometimes will grow their transplants at extremely high EC's (up to 6 EC!) in order to get really nice stocky production plants. Please note that when doing this they use special nutrient formulas designed for this purpose, most of which have potassium to nitrogen ratios of 4:1, much higher than normal, as too much nitrate at this high an EC will easily damage a plant.
(Try this formula if you're interested: calcium nitrate 7 grams, potassium nitrate 0.095 grams, potassium sulphate 9.25 grams, mono potassium phosphate 2.2 gram, magnesium sulphate 5 grams, micromix .02 grams. Slowly raise your EC during veg stage, I would not recommend going above 3 or 4 EC. This is experimental! Do not try on all of your plants at once until you are sure your strain can handle it. All of these ingredients should be available at your local hydroponics store, it is usually called "six pack formula". Be sure to bring your EC back down once you enter floral stage, by the time tufts of pistils are visible you want to be at your ideal EC of 1.5-1.8.)
Try not to change the EC too quickly as a sharp drop can cause root damage. This also goes during your final flushing period when you want to eliminate all fertilizer from the medium ? lower the EC over a couple of days, as the sudden change in salt level will harm the roots.
When growing hydroponically, the only way of manipulating water availability is with the EC, while in soil we may also use the moisture level of the medium to the same ends. Many growers are under the mistaken impression that the EC and pH of their nutrient solution remains the same when applied to the soil. This in not the case, and you must test the soil in order to have a true
picture.
To test your soil, take a sample from the center of the root zone at the side of the pot (don't worry the torn roots will be fine). Mix the soil with 2 equal parts distilled water and let sit for 20 minutes. Once the time is up take an EC reading and multiply this number by 2.4 (this takes into account the dilution and the pore space factor) this will give you an accurate picture of the EC the roots are actually being exposed to. The pH should also be checked at this time. It is not feasible in soil to maintain an exact EC at all times, what we need to try and avoid is EC's climbing much above what we want and plants going for long periods with very low EC's.
A frequent mistake marijuana growers make is over-emphasizing the need for a plant grown in soil to dry out completely between waterings. Cannabis does like dry feet but this simply means that the root zone must not be kept extremely wet at all times. Keep in mind that if the soil has an EC of 1.8 and then dries out completely the amount of salt remains the same, causing the EC to double or more.
As a general rule, during the vegetative stage you should keep your plants a little on the drier side as this will restrict cell elongation, creating a shorter noded plant structure capable of creating a dense bud cluster in the floral stage. (Unless of course you are using the high EC method described above, in this case you must not let your soil get too dry because of the increased fertilizer level you will create.) Maintain this level of moisture into the first 14 to 20 days of 12/12 to minimize internode stretch.
As soon as early flowering begins you need to increase soil moisture to a nice evenly moist (not soaked) level to maximize bud expansion. Growing marijuana too dry during this stage will adversely affect your overall yield, as will having too high an EC in the medium.
tight internodes
example of tight internodes(closeup)
long internodes
example of long internodes (closeup)
leaf chlorosis (yellowing)
http://www.cannabisculture.com/v2/articles/1536.html
Also, big healthy green leaves are crucial to making big dense buds.
1. Never remove a leaf from the plant, unless the leaf is already about to fall off on it's own due to over-maturity(or accidental/premature death). Pruning shade leaves to increase light reaching lower buds is not a wise choice. You will never make up for the loss of production to the top of the plant from whatever may be gained on the lower part. The answer to that is to provide sufficient lighting to the lower buds, optimal reflectivity is the best way to get more light to the lower parts of the plant. Or just remove them from the plant(why you would is another argument really, so I won't be addressing it here, but I don't recommend it either). Light loses intensity/strength based on distance from the source. So you gain relatively little from doing anything except moving the source closer to the plant, or vise versa. Leaves serve a very important purpose in maintaining plant health and vigor. Buds are not going to efficiently feed themselves without them. LEAVES ARE BUD FEEDERS, NOT BUD FOOD!
2. Never flush. Pre-harvest flushing is such a fat dense bud killer it's not even funny. Just in the hopes of getting a better flavored smoking material. Which you won't. It may actually worsen the flavor, density, smokability, and/or potency of the buds. MINIMALLY you will lose harvested/dried weight. You're essentially starving the plant to death. When you should be feeding it what it needs to grow the BIGGEST DENSEST buds at the point in it's life cycle when that's exactly what it wants to do. Yes, I know the article mentions it, but I don't see that as a recommendation. Just how to incorporate the method, if desired. Which you should desire not, trust me. Much foolishness. Mother Nature, the best grower in the universe, doesn't flush her plants, and nor should you. AND IT WILL ACTUALLY INCREASE INTERNODE LENGTH/STRETCH, GUARANTEED!!!
Lastly, stems. Bigger, denser, heavier buds also need bigger thicker stems to pipe in all the nutritional building blocks used to make them, and to help support their weight. While controlling internode length is very effective at improving density, providing a simulated breeze of adequate strength is THE ONLY non-nutritional way to build a larger-diameter/sturdier stem structure. When the plant grows to resist the forces of wind it will naturally respond to it by thickening it's stems/branches. This benefits the buds come flowering time by allowing them to grow much larger and/or faster. In this sense you can force the plant to grow as if it were older, taller, and/or heavier than it really is. You also will have less need to support the plant by manual methods(stakes, strings, cages, etc.)
K
kooldave67
My indoor is 76 day time and 68 at night on 12/12. Have never changed this in any of my grows. Remember this is only a temp guide,it depends on what the plant wants and you will know in the first 30 days of veging because the plant will show signs that can point you in the direction of what it wants.
Last edited:
There's plenty of research anon0988,just gotta actually do your homework.
I copied this from the Hightimes 2006 Seed Buyers Guide...
Taken from High Times' 2006 Seed Guide.
What's The Dif?
Manipulating Plant Performance with Professional Temperature Control.
By Proffessor Potter.
Growers know that ambient temperatures play an important role in plant development.You don't have to have a Ph.D. in plant physiology to understand that temperature determines the rate of bio-chemical reactions,the relative amount of products created by enzymes within plant cells,and those products' transport and allocation in plant tissues.Temperature also influences the production,interaction and activity of plant hormones.Mayb a Ph.D. would help,but even a novice grower can use advanced temperature control to help grow a better crop.Here is the gist of it.
Plants are generally and obviously seen to be best adapted to temperature regimes in which daytime growing temperatures are,on average,higher than nightime growing temperatures.However,for reasons not fully understood-or at least not fully explained here-the difference in day/night temperature influences stem and internodal elongation.Higher relative night temperatures result in plants with shorter internodes (the distance between branches or nodes).By creating night temperature equal to or higher than day temperatures in the growing area,we can grow shorter,more compact plants without sacrificing flower number or size.This method of temperature control is called DIF.
DIF is not an acronym;it's simply short for "difference."DIF is the difference in average day temperature (ADT);in practice,the "average" is usually dropped and the equation is given as DT/NT.If your growing area's temperature is 76F during the day and 70F at night,then the DIF is +6.The term DIF was originally coined to refer to conditions in which the average day temperature is lower than the average night temperature,producing a negative DIF.For example,if DT= 76F and NT= 85F then the DIF= -9F.
Dr. Royal Heins,a distinguished proffessor of horticulture at Michigan State University,coined teh term DIF.He recognized the phenomenon of plant response to higher night than day temperatures;it was an accidental discovery that arose from and experiment being conducted by one of his students.DIF is not a natural phenomenon-in nature,night temperature seldom exceeds day temperature-and was unknown to horticulture until the 1980's.By manipulating it,we can confuse the natural hormone balance in the plant to influence it's growth.
A partial explanation for the DIF phenomenon is that the syntesis or action of a gibberelic acid,which contributes to cell-wall elongation,is inhibited.Similarly,auxin,anot her plant hormone that influences cell elongation,may also be inhibited.Given that plant hormones seldom work alone,it may be a combination of these or other factors.No one really knows for sure,but we are working on it.Whatever the reason,the effect of the DIF means that the plant will grow more compactly with warmer night temperatures than with cooler-than-day night temperatures.
DIF is useful in negating the effect of plant crowding,which,due to the plants response to the far-red light (heat) emitted by it's neighbors,stimulates stem elongation.The influence of radiant far-red light from non-biological sources also cuase stem elongation and "stretching" under lower light conditions.Under high light and otherwise optimal conditions,DIF is used for reducing plant height and promoting denser flower formations.
Some of the first research with the DIF was done with Easter lillies and poinsettias,bot important horticulture crops.In commercial horticulture,it is important to track height and time blooms in order to meet specific target dates for marketing.
The DIF,and variations of it,are now used by professional plant growers around the globe for crops as diverse as corn,sage,tomatoes,impatients and,occasionally,cannabis.
How much should the DIF be?It depends on the crop.Ester lillies show the greatest effect at a DIF of -15 degrees celsius,poinsettias at -12 degrees celsius,and fuchsia at -20 degrees celcius.For some crops,there are tadeoffs;the greatest effect isn't necessarily the most economic or physiologically desirable.Additonally,the DIF change from positive to zero has a more marked effect than from zero to negative.Commercially,the typical maximum DIF is usually no more than -6 degrees celsius and is typically -2 or-3 degrees celsius,since night heating and cooling raises costs.Further,there is a tradeoff between hight control and flowering time,leaf area and fruit development.Reducing the day temperature to accomadate DIF reduces the growth rate in heat-loving plants,and a high negative DIF has been demonstrated to reduce relative flower number and size in several species.
For cannabis,the best DIF for day/night temperatures is probably zero if you grow in a medium-light garden and maintain day temperatures of 80F - that is,day and night time temperatures should be the same.In a low-light garden,a negative DIF may actually have a detrimental effect,as seen in chrysanthemums.A possitive DIF has traditionally been recommended for indoor cannabis horticulture,and it may be desirable for a low-light garden.But if you have free reign to control temperature and you grow in a medium- or high - light garden,you might try a DIF of -2 degrees celsius or -3 degrees celsius.But given the cost and difficulty of heating and cooling,a high-light growing area-especially one pushing the plants with supplementary Co2 and higher day temperatures-might require and alternative.
There is an alternative to using the DIF as a function of DT and NT.This technique doesn't have an official acronym,but in commercial growing it's referred to as "cold-air dump" *CAD).This is when the temperature in the growroom is lowered after sunrise (lights on) to below the NT for one or two hours.The CAD relies on the plant's response to the change between night and day.Stem elongation has been found to be at it's highest rate at the end of the dark period and the beginning of the light period.Cooling during only the first two hours of the day dramatically stem elongation in poinsettias.This technique is usually the most economocal and is used more frequently in commercial flower production.
In a cannabis growing operation that I am familiar with,a more refined version of CAD is being used with excellent results.This "invisible greenhouse" hydroponics operation uses 85 percent of available sunlight,with a supplemental 400-watt high-pressure sodium light and Co2 fetilization up to 1200 ppm.With the high-light and Co2 fertilization,dat temperatures are run at 85F-90F and the growth rate is outstanding.Because of the high DT,raising the NT to create a negative DIF would be uneconomical and would probably stress the plants.In this operation,the day temperature is extended for several hours after dusk,then gradually diminished to a night temperature of 27 degrees celsius.One hour befor "dawn" (lights on),it is raised to 30 degrees celsius and then lowered to 25 degrees celsius to stimulate a CAD,before returning to the day temperature of 30 degrees celsius.The effect is most notable with sativa cultivars,but indica cultivars also do exceptionally well in this system.Internode length is shortened,and the flowering tops are dense and compact but very large.This is only one of the horticultural techniques used in the operation;however,the effect is noticeable and seperable from other influences in this high-yeild system.
Manipulating the day and night temperatures is a proven method in the world of horticulture,has helped reduce the use of chemical growth regulators,and is used to increase productivity and assist with timing crops to the day and hour.The cold-air dump similarly is coming into it's own as a cropping method.So DT/NT or CAD,what's the DIF?For cannabis,either can be used to improve plant performance,depending on what growing parameters are used.It's just a matter of how you do that funky stuff you do.
I copied this from the Hightimes 2006 Seed Buyers Guide...
Taken from High Times' 2006 Seed Guide.
What's The Dif?
Manipulating Plant Performance with Professional Temperature Control.
By Proffessor Potter.
Growers know that ambient temperatures play an important role in plant development.You don't have to have a Ph.D. in plant physiology to understand that temperature determines the rate of bio-chemical reactions,the relative amount of products created by enzymes within plant cells,and those products' transport and allocation in plant tissues.Temperature also influences the production,interaction and activity of plant hormones.Mayb a Ph.D. would help,but even a novice grower can use advanced temperature control to help grow a better crop.Here is the gist of it.
Plants are generally and obviously seen to be best adapted to temperature regimes in which daytime growing temperatures are,on average,higher than nightime growing temperatures.However,for reasons not fully understood-or at least not fully explained here-the difference in day/night temperature influences stem and internodal elongation.Higher relative night temperatures result in plants with shorter internodes (the distance between branches or nodes).By creating night temperature equal to or higher than day temperatures in the growing area,we can grow shorter,more compact plants without sacrificing flower number or size.This method of temperature control is called DIF.
DIF is not an acronym;it's simply short for "difference."DIF is the difference in average day temperature (ADT);in practice,the "average" is usually dropped and the equation is given as DT/NT.If your growing area's temperature is 76F during the day and 70F at night,then the DIF is +6.The term DIF was originally coined to refer to conditions in which the average day temperature is lower than the average night temperature,producing a negative DIF.For example,if DT= 76F and NT= 85F then the DIF= -9F.
Dr. Royal Heins,a distinguished proffessor of horticulture at Michigan State University,coined teh term DIF.He recognized the phenomenon of plant response to higher night than day temperatures;it was an accidental discovery that arose from and experiment being conducted by one of his students.DIF is not a natural phenomenon-in nature,night temperature seldom exceeds day temperature-and was unknown to horticulture until the 1980's.By manipulating it,we can confuse the natural hormone balance in the plant to influence it's growth.
A partial explanation for the DIF phenomenon is that the syntesis or action of a gibberelic acid,which contributes to cell-wall elongation,is inhibited.Similarly,auxin,anot her plant hormone that influences cell elongation,may also be inhibited.Given that plant hormones seldom work alone,it may be a combination of these or other factors.No one really knows for sure,but we are working on it.Whatever the reason,the effect of the DIF means that the plant will grow more compactly with warmer night temperatures than with cooler-than-day night temperatures.
DIF is useful in negating the effect of plant crowding,which,due to the plants response to the far-red light (heat) emitted by it's neighbors,stimulates stem elongation.The influence of radiant far-red light from non-biological sources also cuase stem elongation and "stretching" under lower light conditions.Under high light and otherwise optimal conditions,DIF is used for reducing plant height and promoting denser flower formations.
Some of the first research with the DIF was done with Easter lillies and poinsettias,bot important horticulture crops.In commercial horticulture,it is important to track height and time blooms in order to meet specific target dates for marketing.
The DIF,and variations of it,are now used by professional plant growers around the globe for crops as diverse as corn,sage,tomatoes,impatients and,occasionally,cannabis.
How much should the DIF be?It depends on the crop.Ester lillies show the greatest effect at a DIF of -15 degrees celsius,poinsettias at -12 degrees celsius,and fuchsia at -20 degrees celcius.For some crops,there are tadeoffs;the greatest effect isn't necessarily the most economic or physiologically desirable.Additonally,the DIF change from positive to zero has a more marked effect than from zero to negative.Commercially,the typical maximum DIF is usually no more than -6 degrees celsius and is typically -2 or-3 degrees celsius,since night heating and cooling raises costs.Further,there is a tradeoff between hight control and flowering time,leaf area and fruit development.Reducing the day temperature to accomadate DIF reduces the growth rate in heat-loving plants,and a high negative DIF has been demonstrated to reduce relative flower number and size in several species.
For cannabis,the best DIF for day/night temperatures is probably zero if you grow in a medium-light garden and maintain day temperatures of 80F - that is,day and night time temperatures should be the same.In a low-light garden,a negative DIF may actually have a detrimental effect,as seen in chrysanthemums.A possitive DIF has traditionally been recommended for indoor cannabis horticulture,and it may be desirable for a low-light garden.But if you have free reign to control temperature and you grow in a medium- or high - light garden,you might try a DIF of -2 degrees celsius or -3 degrees celsius.But given the cost and difficulty of heating and cooling,a high-light growing area-especially one pushing the plants with supplementary Co2 and higher day temperatures-might require and alternative.
There is an alternative to using the DIF as a function of DT and NT.This technique doesn't have an official acronym,but in commercial growing it's referred to as "cold-air dump" *CAD).This is when the temperature in the growroom is lowered after sunrise (lights on) to below the NT for one or two hours.The CAD relies on the plant's response to the change between night and day.Stem elongation has been found to be at it's highest rate at the end of the dark period and the beginning of the light period.Cooling during only the first two hours of the day dramatically stem elongation in poinsettias.This technique is usually the most economocal and is used more frequently in commercial flower production.
In a cannabis growing operation that I am familiar with,a more refined version of CAD is being used with excellent results.This "invisible greenhouse" hydroponics operation uses 85 percent of available sunlight,with a supplemental 400-watt high-pressure sodium light and Co2 fetilization up to 1200 ppm.With the high-light and Co2 fertilization,dat temperatures are run at 85F-90F and the growth rate is outstanding.Because of the high DT,raising the NT to create a negative DIF would be uneconomical and would probably stress the plants.In this operation,the day temperature is extended for several hours after dusk,then gradually diminished to a night temperature of 27 degrees celsius.One hour befor "dawn" (lights on),it is raised to 30 degrees celsius and then lowered to 25 degrees celsius to stimulate a CAD,before returning to the day temperature of 30 degrees celsius.The effect is most notable with sativa cultivars,but indica cultivars also do exceptionally well in this system.Internode length is shortened,and the flowering tops are dense and compact but very large.This is only one of the horticultural techniques used in the operation;however,the effect is noticeable and seperable from other influences in this high-yeild system.
Manipulating the day and night temperatures is a proven method in the world of horticulture,has helped reduce the use of chemical growth regulators,and is used to increase productivity and assist with timing crops to the day and hour.The cold-air dump similarly is coming into it's own as a cropping method.So DT/NT or CAD,what's the DIF?For cannabis,either can be used to improve plant performance,depending on what growing parameters are used.It's just a matter of how you do that funky stuff you do.
What I was saying is that my answer had zero research behind it, other than just reading these forums. I'm sure there's tons of research out there, I just wanted to make clear that my answer wasn't based on any of it.
Swan Lee
Member
Hey Greendream and Jnugg,thanks so much for those articles,they certainly covered everything ,,,and more.
I raised my NTs to 70ish a few days ago and they seem happier all ready.the Kandy Kush nearest the heater,that i was giving another week or so,is looking just about ripe for chopping
If i could work out how to post pics,then i would.
I raised my NTs to 70ish a few days ago and they seem happier all ready.the Kandy Kush nearest the heater,that i was giving another week or so,is looking just about ripe for chopping
If i could work out how to post pics,then i would.
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I allow no more than an 8-10* drop from daytime temps.
Benjamin Check
Member
77-82 day, 72-75 night depending on ambient outside temp. My setup is in a cool basement so that helps a whole lot.
You want the ac removing water from the air.
I use a split and it stays pretty close day and night.
The dehuey helps keep it warm when the lights are off.
During stretch I try to remember to turn the temp up a few degrees when lmy lights go out to keep the DIF lower
I use a split and it stays pretty close day and night.
The dehuey helps keep it warm when the lights are off.
During stretch I try to remember to turn the temp up a few degrees when lmy lights go out to keep the DIF lower
