High RH Levels & Leaf Curling

[ArtistZanner]

So I'm back to moan and groan yet again. Things have been going well and I was planning on flipping to flowering in about 10 days. My plants aren't huge, but I have some of different sizes due to not getting my lighting right at the beginning, but for the most part they are close in size.
Two things happening that have me concerned. The first is that my humidity (despite having a full-size dehumidifier in the room) is running high. We are having some very strange weather here in the UK, plus a lot of rain, which equals high humidity. Now, I will admit that I've been struggling to get my humidity below 64%, even before the recent spike, but now I am running between 70-73%. I am worried how I will deal with that when I go into flower mode, unless the weather goes back to being much cooler. I've removed my bucket of water that I had in there, and I am emptying my drip saucers after watering, so there's no standing water to contribute to the humidity issue.

The second issue I'm not sure what the problem is precisely is that my leaf edges are curling inwards, not drastically, but enough that I know something is amiss. I have a bamboo outside that does that when we have very hot days. I generally water it, and it's fine. I've recently watered my plants, and because I'm fearful of overwatering, I'm going to leave it a few days before I water again. The leaves aren't burnt at all and otherwise look healthy, they're just curling a bit inwards. I've lowered the intensity of the lights (dimming), thinking that might be the issue, but I'm actually seeing more plants doing this (though not all of them). Could it be that it's too hot in the room? While I think that could be it, it's never above 68F in there, so that seems odd. I have my fan pointed upwards to try and get some of that heat blown away. Do I need another fan? Hopefully someone can help get me back on the right track. Thanks in advance.

 

[Fnipernackle]

So I'm back to moan and groan yet again. Things have been going well and I was planning on flipping to flowering in about 10 days. My plants aren't huge, but I have some of different sizes due to not getting my lighting right at the beginning, but for the most part they are close in size.
Two things happening that have me concerned. The first is that my humidity (despite having a full-size dehumidifier in the room) is running high. We are having some very strange weather here in the UK, plus a lot of rain, which equals high humidity. Now, I will admit that I've been struggling to get my humidity below 64%, even before the recent spike, but now I am running between 70-73%. I am worried how I will deal with that when I go into flower mode, unless the weather goes back to being much cooler. I've removed my bucket of water that I had in there, and I am emptying my drip saucers after watering, so there's no standing water to contribute to the humidity issue.

The second issue I'm not sure what the problem is precisely is that my leaf edges are curling inwards, not drastically, but enough that I know something is amiss. I have a bamboo outside that does that when we have very hot days. I generally water it, and it's fine. I've recently watered my plants, and because I'm fearful of overwatering, I'm going to leave it a few days before I water again. The leaves aren't burnt at all and otherwise look healthy, they're just curling a bit inwards. I've lowered the intensity of the lights (dimming), thinking that might be the issue, but I'm actually seeing more plants doing this (though not all of them). Could it be that it's too hot in the room? While I think that could be it, it's never above 68F in there, so that seems odd. I have my fan pointed upwards to try and get some of that heat blown away. Do I need another fan? Hopefully someone can help get me back on the right track. Thanks in advance.

Inward curl can be for a few reasons. Could we get a photo of the leaves and whole plant? It'll help diagnose.

Humidity is tough to deal with sometimes, but you can help your plants out a lot by increasing airflow and air exchange. As long as the air is moving through the entire canopy, your chances of moisture buildup and mold are greatly reduced.

If it isn't already too warm in your grow room, a small space heater could help. Raising temps by even a degree or two can help with your RH, air holds more moisture the warmer that it is.

 

[PooToe]

Inward curl can be for a few reasons. Could we get a photo of the leaves and whole plant? It'll help diagnose.

Humidity is tough to deal with sometimes, but you can help your plants out a lot by increasing airflow and air exchange. As long as the air is moving through the entire canopy, your chances of moisture buildup and mold are greatly reduced.

If it isn't already too warm in your grow room, a small space heater could help. Raising temps by even a degree or two can help with your RH, air holds more moisture the warmer that it is.

Agree. Please post the temp and humidity ranges you are experiencing currently. Are your humidity highs after lights off or during lights on?

As @Fnipernackle mentioned, raise the airflow in the tent to allow the exhaust fan to remove it from the tent environment to keep mold at bay and increase the amount of water vapor being able to be held in the air. I like to run my grows at around 80° - 82° air temp. This usually lands me at around 77° leaf temp. 77° leaf temp is the temp that leaves are photosynthesizing the most efficiently.

Look into VPD(Vapor Pressure Deficit) to find where your optimal range is.

Your leaf curl is probably too much light. I would back it off some and see if that helps. If you have a way to measure the PPFD in your tent you can dial in the amount of light the plants need. I have an android phone and use an app called Tent Buddy. Iphones have Photone for their app. If you want to spend the coin you can buy a dedicated light meter. I would recommend one from a company called Apogee. Look into DLI(Daily Light Integral) to better pinpoint the plants light needs at all stages of growth.

I like to use the light pot method to determine when it is time to water but overwatering comes from watering too frequently not too much. Obviously you don't want to flood the pot but no one watering event will bring on overwatering. It's the frequency that causes overwatering symptoms. Cannabis likes a moist to wettish soil. When you initially water, the roots get submerged in the high water content and the O² exchanges it needs to do get slowed down since water holds less O² than atmosphere. Once the plant has taken up enough of the water out of the soil and has reached an equilibrium, in regard to O² availability to the roots, the plant will increase its O² exchanges. This is where the real uptake happens. This is also why it is recommended to allow a dryback period before you water again to allow the soil to reach that equilibrium and maximize O² exchange. Once you master this you can move onto a method called fertigation that increases the O² exchange time buy keeping your soil water content at the equilibrium level for longer than watering in the traditional way.

Correct your plant issues before you flip. Flipping a sick/stressed plant guarantees low dry yields.

The following information really helped me fill in the gaps as to what is happening below the soil line and how my choices in regard to media and pot size and shape affect the grow. It also showed me why and how to water properly. I am not the author.

This will be a long read based on my personal knowledge, opinions, research and others work to consolidate information for our members. I'm not presenting my opinions as facts so take from this what you like. I will be putting it in subsection format for easy reference.

First I want to make an important point to take into consideration before reading. The tap root will grow directly downwards to the bottom of the container before spreading out.

PERCHED WATER TABLE

What is it?

The perched water table is basically the height of the saturation zone where capillary action and gravity cancel eachother out. This area will be saturated with water and will be responsible most growers issues with watering practices especially in soil grows.

WHAT IS CAPILLARY ACTION

CAPILLARY action is is the combination of the cohesive and adhesive properties of water.

In short adhesion is water clinging to the media (think of it like wicking or soaking up)

Cohesion is where the water clings to itself.

So as the water is wicked up (adhesion) it pulls more water with it through Cohesion and at the point gravity and these properties cancel eachother out is the perched water table.

This perched water table will always remain the SAME HEIGHT and will always stay saturated unless taken up by the plants or evaporates when the pot dries out. No matter the container height, depth or volume of media. So if a tall skinny container had a perched water table of 1" then a short wide one of the same media will also have a perched water table of 1". Which means the ratio of water to air in a wide pot will be higher than a tall skinny pot which will have a higher air to water ratio... keep this in mind as we get further.

Different media's have different perched water tables. A more absorbent media will have a higher perched water table than a less absorbent media... REMEMBER THIS as it makes a big difference on pot selection for your media.

DIFFERENT MEDIA

Water holding capacity is directly related to the height of the perched water table so soils with more clay or silt and less sand will have a higher perched water table than those with more sand because sand is a larger particle.

The larger the overall particles of the media the lower the perched water table and better the drainage.

By adding things like perlite or vermiculite (while vermiculite is good at absorbing water it also improves drainage so its helpful in keeping a more even level of moisture throughout the media while increasing drainage due to its size) we can lower the perched water table by reducing the wicking (adhesion) ability and creating more space between particles overall reducing the cohesion effect and inturn the height of the perched water table.

Media like peat based or coco have a much higher drainage and lower perched water table than soil and are therefore less susceptible to over watering but will require more frequent watering due to the lower water holding capacity.

Adding things like perlite or hydroton to the bottom of the pots will NOT reduce the water table but instead raise it. This is because as I said the height of the water table will not change for a given media. So if you add things like that to the bottom you are essentially just moving the water table up.

Basically, the larger the particles IN the media the better drainage and lower the water table.

If you want to see the height of your perched water table use a clear cup with drain holes fill with media and saturate it. Wait a few hrs for drainage and then come back and look. You can see the difference in the varying media's if you want to experiment.

If you feel you have over watered or your perched water table height is too high you can simply tilt your pot on a 45 degree angle and release more water from the media as runoff. To help visualize think of it this way if you have a perched water table of 2”. You can draw an imaginary horizontal line at that height, when you tilt the pot you have less media below that line and therefore you will have less water in the pot after tilting it.

POT SIZE

I have already covered this a bit but my opinion is if you are using a media with a higher water table you will benefit from taller narrower pots and if using a media with a lower perched water table the shorter wider ones may benefit you depending on your watering practices.

I prefer the taller over wider no matter the media as I choose to water often and have a higher air holding capacity and lower water table but that can work against you if you can't water as frequently and as plants grow it can greatly increase the frequency required as the roots will be pulling the water out of that saturation zone quickly. So you may want to use taller pots for small plants and transplant into a wider one as they grow.

You also don't want a pot that's to tall and the top portion of the media is drying out to fast while the bottom is wet.

Let's use seedlings as an example take a solo cup or a large container... the water table will be the same height in either. I see sooo often ppl trying to water a tiny bit in circles or mist the surface and for lack of other words IT DRIVES ME NUTS. Why? Because the roots are so shallow they are not at risk of being over watered. Remember though tap roots grow straight down so we to be mindful as they grow depending on the gas exchange of the media that the majority of roots are not sitting in the saturated zone with poor gas exchange because this will cause lack of oxygen that we incorrectly refer to as overwatering which is actually the cause not the symptom.

It's important to fill containers to the top to give us a good amount of space above the perched water table that high in o2. If you fill a solo cup halfway with soil it's likely to be sitting in the saturation zone and will not do well.

Also going to make the point that plants will be most susceptible to overwatering when the roots first hit the bottom and spread out until they fill the bottom and start moving back up out of the saturation zone. So, again, it may be more beneficial to use a taller narrow pot for the early stages of growth (2-4 weeks depending on growth) and transplant into a wider pot as you go. After the transplant almost all of the roots will be above the saturation zone and it becomes much harder to over water. New roots will again work their way down into the saturation zone but you will have plenty above so it's less likely to over water and why up potting as you go, I see as a benefit instead of starting in a large wide container.

POT MATERIAL

Some prefer plastic others fabric, air pots etc.

This can affect the perched water table by evaporation as the lager the exposed surface area the more evaporation that occurs from the media in say fabric pots. This imo has a few benefits.... slightly reducing the perched water table but more so the exposure for gas exchange that's happening and that's a good thing for o2 levels in the root zone that I feel are directly related to growth rates and I'll explain why going a bit off topic for a second.

It's no coincidence that the fastest growing media's have the highest amounts of o2 and gas exchange.... for eg aeroponics have unlimited to rich o2 and water. Hydro similar with slightly less o2, soilless media's such as coco and I would possibly include peat and last soil. If you notice they are in order of growth rates and its not hard to see the difference in thier air holding capacity in that order. And the fact that larger particles also have a better gas exchange rate. This is important because the plants take in oxygen and expel co2 in the rootzone as do the microbes on top of that so good gas exchange is important for both.

Just a note... air pruning has nothing to do with the benefits of fabric pots all it does is signal the roots to grow in a different direction.

But let's get back on topic of watering and how it's affected.

TEMPERATURE AND HUMIDITY

The warmer the temps the more evaporation occurs.

The lower your humidity the more evaporation occurs

The more surface area exposed to air movement (wind) the more evaporation.

Think those don't need an explanation. But the difference in pot material coupled with these environmental factors will have an impact on your watering needs.

The temperature of the media not only affects evaporation but also directly affect the temperature of the plant and leaf temps. This has a large impact on nutrient uptake and transportation.

First let me say that this next part is opinion and I will give my reasoning for my opinions. With the exception of hydro (leaving this part out as this post is about watering not hydro) roots like to be about the same temperature as the leaves contrary to what's talked about from many prominent growers in the industry but not all like Dr Bruce Bugbee. IMO ideal root temps are the same as ideal leaf temps and overall plant temps especially since the root temps have a large impact on the plant and leaf temps. What are ideal temps imo and many studies show that leaf temps (NOT AIR TEMPS) of around 77f are most efficient. So how does a cool rootzone impact the plants negatively? Well it's 2 fold because of the cool temps the viscosity (measument of flow rate) of the sap will decrease so its harder for the plant to move the nutrients through the plant. The other is absorption and one fact is that in a cooler rootzone the concentration of nutrients is higher (but you just said it slows absorption)! Well, it does as the nutrients build up in the roots it can absorb less and this has a direct impact negatively on the plant. It may appear to be overwatered because the plant is now struggling to take up and use oxygen. Add that to the slowed transpiration rates and you have the same symtom many refer to overwatering which againnos lack of o2. Now take a cold rootzone where the plants slow water uptake and then add the saturation zone to it and you can see the road to correction and recover is a long one and can have huge impact on growth and yields.

So get your pots up off the floor

WET AND DRY CYCLES

in soil and peat with higher water tables or with wider pots or combination of wet and dry cycles are important. This is to allow the dry back (including the uptake of water from the saturation zone) to prevent symptoms of over watering and help with o2 levels. Remember the majority of roots will end up in the saturation zone with these media's or with wider pots. Which can become depleted of o2 quickly as gas exchange is lower in water and media made up of smaller particles. This is where pot size and shape are important for the size of plant. You have a small plant in large container and there is no way it can take up enough of the water in the saturation zone fast enough to get air exposure in a media that has low gas exchange and majority of the roots. So it's important to choose a pot size that will allow for this. It's also why using the finger method to gage watering is poor and lifting the pots is much better... when they are light you know they have taken up a good portion of the saturation zone and are ready to be watered again.

This is much less of an issue when using soilless like coco or peat/perlite.

 

[ArtistZanner]

Okay, so here's 5 photos. Numbers 1 and 2 are of the same plant, showing the plant and then showing the curling at the top. Photos 3 and 4 are of another plant, showing leaf curling, and then the plant. I tried adding another photo to show that not all my plants have that leaf curl, in fact, more than half do not. But each time, for some reason, it kept putting that photo at the beginning instead of at the end. I can post separately if you want to see it.
So earlier today, when I went to turn on the lights, the humidity was at 82%, which is very abnormal and the temperature was about 67F. Here in England, yesterday was very warm and today was extremely warm, plus we're having rain, and mild nights. It's supposed to get colder, so that will help some. Just now when I went to take photos, the humidity was down to 77%, but that's only because I left the door open a bit to let in cool air. My temperature was about 66-67F. Now, I do have a heater in there and normally I try to get the temperature up to about 70F or higher if I can, but I turned it off earlier when I wasn't sure if the plants were responding to it being too warm in there. I have a fan that I let oscillate around the space all the time. So, my space is a bit different from what a lot of people do. I don't have a tent. I am growing in a building that used to be an office (it's behind our house) The problem is, all but one window is sealed. And the window that's not sealed is too far away from my growing area, and I can't really get to it from all the stuff that's in there. The building is quite big and we now use it for storage. What I'm saying is that while I can easily run a fan, I don't have the ability to run an intake fan as well. When the lights are on, I do sometimes open the door to allow some cooler air in, but obviously I cannot do that when lights are off, and I won't leave it open when I'm in bed. The thing is, until this warm spell, I wasn't having these really high humidity numbers, but I still was having numbers higher than I would like. I run a dehumidifier 24/7 and it does remove moisture quite well. I'm not sure what else to do. The humidity, I feel, will change when cooler weather comes, but the leaf curl is worrying me.

Oh, and just to say, I have pot lifters under all of my plants, meaning that they have about 2" between the bottom of the fabric pot and the saucer where the water drains off. I feel that lifting them up allows air to get under instead of the bottom always being wet, as it was before I bought them. I may not be calling them by their proper name, but hopefully you get what I mean.

 

[PooToe]

I usually run my indoor grow air temps around 80° - 82°/26C - 28C. This usually yields me a leaf temp of around 77°/25C. There are many reports and studies that show that 77°/25C leaf temp is where leaves are photosynthesizing most efficiently. If you can run your room at a higher temp it will assist your dehu in removing moisture.

Are you able to setup a box fan in the window that will open? Sounds like the space is fairly large so I'm thinking a box fan at the open window will ventilate the entire space, your plants included.

Now.....if it is unusually humid outside ventilating more humid air into your space is going to be counterproductive. What this means is, aside from raising the temperature in your grow space there really isn't much more you can do to control the environment other than installing an entire environmental system to give you better control over your environment.

The fan leaves look good, maybe slightly overwatered, but they still look relatively good compared to the young curling leaves. Something is stressing the plant out. The curling could be the plants response to the high differentials you currently have going on. High humidity with low temp. Since you can't really do much about the humidity I would look to firing up the heater and raising the temp in your space. What are the temp differentials between lights on and off? Could be the swing is affecting them.

 

[ArtistZanner]

I usually run my indoor grow air temps around 80° - 82°/26C - 28C. This usually yields me a leaf temp of around 77°/25C. There are many reports and studies that show that 77°/25C leaf temp is where leaves are photosynthesizing most efficiently. If you can run your room at a higher temp it will assist your dehu in removing moisture.

Are you able to setup a box fan in the window that will open? Sounds like the space is fairly large so I'm thinking a box fan at the open window will ventilate the entire space, your plants included.

Now.....if it is unusually humid outside ventilating more humid air into your space is going to be counterproductive. What this means is, aside from raising the temperature in your grow space there really isn't much more you can do to control the environment other than installing an entire environmental system to give you better control over your environment.

The fan leaves look good, maybe slightly overwatered, but they still look relatively good compared to the young curling leaves. Something is stressing the plant out. The curling could be the plants response to the high differentials you currently have going on. High humidity with low temp. Since you can't really do much about the humidity I would look to firing up the heater and raising the temp in your space. What are the temp differentials between lights on and off? Could be the swing is affecting them.

Thanks for responding, and giving some good advice.
In all honesty, I really don't think I can set anything up at that one window, it's an odd window. However, I can increase the temperatures by running my heater at a higher setting.
I literally just watered all the plants last night, that could be why they look "overwatered". I don't just water them willy nilly, I literally stick my fingers down into the soil to feel how dry or wet it is. I try to err on the side of keeping them drier more than wetter. I don't think there's a great difference in temperatures or humidity between lights on and lights off. The lights are off during the day, and are on the other 18 hours, which is mainly evening and some day hours. Like I mentioned, we're having some very unusual warm temperatures, but the weather prediction is for cooler temps tomorrow, so hopefully that happens. My humidity tends to go down a bit when it's cooler outside. Can I ask, does it make a huge difference if my fan is pointed upwards towards the ceiling or if it should be pointed more at the plants? I was pointing it at the plants, but on a low setting. When the humidity spiked, I pointed it upwards and put it on the highest setting. Not sure if that's doing anything beneficial or not. Do you think my lights could be the culprit? Should I continue leaving the lights dimmed, or do you think the lights aren't anything to do with the issue?
It makes me feel better to know that you haven't said my plants look like crap, so that's good. Thanks so much for your help.

 

[Newty]

I have 3 tents in the same room, 1 of the tents is drying so I'm not running my dehumidifier.
My Auto tent that I'm growing Blackberry Autos in right now was seeing 60%-65% humidity during lights on and 70%-75% lights off.
My plant leaves were drooping, curling, and wilting.
I even had water on my leaves because of the humidity and the top of 1 of my pots was pretty wet, they get bottom watered so should of been dry
Like I said, didn't want to turn on dehumidifier and screw up the plants i have drying.
My day temps were only seeing 74-75 and I just received the AC Infinity Thermoforge Heater the other day, I hooked up the heater and have it so it turns on at 75 and off at 77 during the day and at night turn on at 68 and off at 71.
Humidity now stays around 50%.
Within 10 hours the water was gone and so was my plant droop, curling, and wilting.
Heater solved all my problems by lowering humidity and drying the plants.

 

[ArtistZanner]

I have 3 tents in the same room, 1 of the tents is drying so I'm not running my dehumidifier.
My Auto tent that I'm growing Blackberry Autos in right now was seeing 60%-65% humidity during lights on and 70%-75% lights off.
My plant leaves were drooping, curling, and wilting.
I even had water on my leaves because of the humidity and the top of 1 of my pots was pretty wet, they get bottom watered so should of been dry
Like I said, didn't want to turn on dehumidifier and screw up the plants i have drying.
My day temps were only seeing 74-75 and I just received the AC Infinity Thermoforge Heater the other day, I hooked up the heater and have it so it turns on at 75 and off at 77 during the day and at night turn on at 68 and off at 71.
Humidity now stays around 50%.
Within 10 hours the water was gone and so was my plant droop, curling, and wilting.
Heater solved all my problems by lowering humidity and drying the plants.

So, it sounds like I should up my heater. I was thinking if my leaves were curling that maybe it was too warm, but I'm realising that the heater will help, and I appreciate the advice by people who clearly know better than me. Thank you!

 

[Newty]

So, it sounds like I should up my heater. I was thinking if my leaves were curling that maybe it was too warm, but I'm realising that the heater will help, and I appreciate the advice by people who clearly know better than me. Thank you!

Is your heater radiant type or does it have a blower?
It it's a blower and in the tent, don't let it blow directly on the plants.

We don't know if there's any other factors that led to it working for me so keep an eye on them and make sure that the heater is actually lowering the humidity and helping the plants.

 

[PooToe]

What I try and do when it comes to fans and air movement is to create a swirl in the tent so that the fan isn't blowing directly on the plants. I'll usually point it at one of the walls at an angle so that it ricochets off the walls and creates a sort of vortex of air movement.

Your fan leaves are telling me that everything was fine up until maybe a week or two ago but this really only applies to the one plant where the new leaves are curling. The others look fine. Was there anything you can think of that may have stressed them out particularly the one with the curling leaves? The others look better. It may be that something happened to stress them out but the weakest is the one that has the curling leaves hence it affected it more than the others.

I think your plants look fine except for the one with the curling leaves but that should even out once the temps and humidity get back into the range they like.

 

[ArtistZanner]

What I try and do when it comes to fans and air movement is to create a swirl in the tent so that the fan isn't blowing directly on the plants. I'll usually point it at one of the walls at an angle so that it ricochets off the walls and creates a sort of vortex of air movement.

Your fan leaves are telling me that everything was fine up until maybe a week or two ago but this really only applies to the one plant where the new leaves are curling. The others look fine. Was there anything you can think of that may have stressed them out particularly the one with the curling leaves? The others look better. It may be that something happened to stress them out but the weakest is the one that has the curling leaves hence it affected it more than the others.

I think your plants look fine except for the one with the curling leaves but that should even out once the temps and humidity get back into the range they like.

@Newty and @PooToe Hi, and thanks for your comments.
I think what happened is that a couple days ago we had really warm weather, and yesterday too. We also had rain, and that's when I noticed the humidity going up too high. But I will also say that the plant that's affected the most used to be under a fairly strong light, and I think that was the start of the problem with the curling leaves. I moved it to another position and I've also dimmed the lights down a bit from what they were. So maybe it's a combination of things. The weather affected my temperatures, that's for sure. I don't have a tent, I'm literally growing in a building that used to be an office, and that building isn't really insulated, if at all. And for those of you that know UK weather, it tends to be fairly damp. I think that initially the plant with the most curled leaves was under a light that was perhaps too strong and that's why the leaves curled. And then we had very warm days Wednesday and Thursday, which spiked my humidity. I also made the mistake of not shutting the door properly, and while normally cooler weather will drop my humidity, on that night, it was very warm and it caused my humidity to rise. So I think the light being too close to the plant, or maybe it was too intense, plus the weather caused my issue. But that's just my guess, I'm really not sure.
Just to clarify on the fan, I generally leave mine to oscillate, should I just aim it in one place instead? I had thought that by allowing it to oscillate, that it would cool off the plants to prevent any fungal issues. But again, I'm just winging it and learning things here and there. Mainly it seems to me that people either grow in tents, or they grow outside. It's hard to get any good information on growing inside in a large room, as I'm doing.
I will say that there are some of my plants that have no leaf curl at all and are looking pretty good. I had wanted to flip my plants in about 8 days, but I don't want to do that until I have the leaf curl sorted. So I'm hoping for cooler temperatures. Our weather forecast says more rain on the way, which means I will need to keep that heater going. Oh, about the heater. It's one of those little box types, but it does have a fan mode, so it does blow heat out. It also has a timer on it, and I can set it to run all night, which is what I usually do. But I will admit, that when things started escalating, I did turn the heater off, because I wasn't sure what my problem was stemming from. I've got it back on now. I'm also going to put a 2nd hygrometer in there because my other one is literally hanging on the wall, which is an outside wall, and I wonder if the numbers are accurate to what my conditions truly are. I will put another one in there and if they jive then I know those are my actual numbers, and if they don't, then I will know that it's picking up moisture from the wall (hopefully I've just made sense with that).

 

[PooToe]

@Newty and @PooToe Hi, and thanks for your comments.
I think what happened is that a couple days ago we had really warm weather, and yesterday too. We also had rain, and that's when I noticed the humidity going up too high. But I will also say that the plant that's affected the most used to be under a fairly strong light, and I think that was the start of the problem with the curling leaves. I moved it to another position and I've also dimmed the lights down a bit from what they were. So maybe it's a combination of things. The weather affected my temperatures, that's for sure. I don't have a tent, I'm literally growing in a building that used to be an office, and that building isn't really insulated, if at all. And for those of you that know UK weather, it tends to be fairly damp. I think that initially the plant with the most curled leaves was under a light that was perhaps too strong and that's why the leaves curled. And then we had very warm days Wednesday and Thursday, which spiked my humidity. I also made the mistake of not shutting the door properly, and while normally cooler weather will drop my humidity, on that night, it was very warm and it caused my humidity to rise. So I think the light being too close to the plant, or maybe it was too intense, plus the weather caused my issue. But that's just my guess, I'm really not sure.

I would agree with this analysis.

Just to clarify on the fan, I generally leave mine to oscillate, should I just aim it in one place instead? I had thought that by allowing it to oscillate, that it would cool off the plants to prevent any fungal issues. But again, I'm just winging it and learning things here and there. Mainly it seems to me that people either grow in tents, or they grow outside. It's hard to get any good information on growing inside in a large room, as I'm doing.

Oscillating is fine. Air movement is to be able to remove the gases that the plant expels along with providing fresh CO² for the plant. If your fan was stationary then I would do as I mentioned prior.

I used to set up grows for people, mostly in garages. As you know, garages usually aren't insulated so they pretty much are left to the elements in regard to temperature and humidity. What I would do when I would do these setups is to first insulate the space with some 2" R-Tech. On your next run if you have the resources to do this I would highly recommend it. You don't have to insulate the entire space just where you will be growing. I had also installed a 3 ton mini split in the room so I could keep the room at whatever temperature I wanted but in the area that I was doing most of the installs the temps in the summer would average around 105° but I could keep the room at a balmy 77° easily. Humidity wasn't a big deal as it didn't really change a whole lot where I would setup most of the garages but a decent sized dehumidifier was employed to be able to keep everything in range.

I will say that there are some of my plants that have no leaf curl at all and are looking pretty good. I had wanted to flip my plants in about 8 days, but I don't want to do that until I have the leaf curl sorted. So I'm hoping for cooler temperatures. Our weather forecast says more rain on the way, which means I will need to keep that heater going. Oh, about the heater. It's one of those little box types, but it does have a fan mode, so it does blow heat out. It also has a timer on it, and I can set it to run all night, which is what I usually do. But I will admit, that when things started escalating, I did turn the heater off, because I wasn't sure what my problem was stemming from. I've got it back on now. I'm also going to put a 2nd hygrometer in there because my other one is literally hanging on the wall, which is an outside wall, and I wonder if the numbers are accurate to what my conditions truly are. I will put another one in there and if they jive then I know those are my actual numbers, and if they don't, then I will know that it's picking up moisture from the wall (hopefully I've just made sense with that).

If you're going to run your heater unattended PLEASE install a smoke detector in your space.

Position your hygrometer so that it is sitting just above canopy height in the middle of your plants. This will give you the most accurate account of what your specs are in the area of your grow room that matters the most. You can hang it off the roof or place it on a chair or box to elevate it to canopy height.

 

[ArtistZanner]

I would agree with this analysis.


Oscillating is fine. Air movement is to be able to remove the gases that the plant expels along with providing fresh CO² for the plant. If your fan was stationary then I would do as I mentioned prior.

I used to set up grows for people, mostly in garages. As you know, garages usually aren't insulated so they pretty much are left to the elements in regard to temperature and humidity. What I would do when I would do these setups is to first insulate the space with some 2" R-Tech. On your next run if you have the resources to do this I would highly recommend it. You don't have to insulate the entire space just where you will be growing. I had also installed a 3 ton mini split in the room so I could keep the room at whatever temperature I wanted but in the area that I was doing most of the installs the temps in the summer would average around 105° but I could keep the room at a balmy 77° easily. Humidity wasn't a big deal as it didn't really change a whole lot where I would setup most of the garages but a decent sized dehumidifier was employed to be able to keep everything in range.

View attachment 2305678

If you're going to run your heater unattended PLEASE install a smoke detector in your space.

Position your hygrometer so that it is sitting just above canopy height in the middle of your plants. This will give you the most accurate account of what your specs are in the area of your grow room that matters the most. You can hang it off the roof or place it on a chair or box to elevate it to canopy height.

Wow, really impressed with that picture, that's awesome. I'm guessing by 2" R-Tech you're talking about something like insulation boards? Yes, that's probably a good idea for me if I do this again. Just to say, the heater I have, if it is moved, or knocked over, it shuts off. It's a pretty good one. But it's easy enough to set up a smoke detector as well, so yeah, I'll do that this weekend. Thankfully my bedroom window looks over the grow building, so that's a plus (of course I know that fire can do a lot of damage before you see it, so yeah, I will do the smoke detector ).

Okay, so some new(ish) developments. I went out a little bit ago to turn on the lights, and of course I'm always curious what the temperature and humidity are like. So temperature is about 67F and humdity was 68%. Not great, but better than it has been. I have put another hygrometer in the room, but I haven't placed it as you suggested. I will do that later before bed. I understand about putting it at canopy height, will it be okay under the lights, or should I keep it out of direct light?
We're having more rain tonight, so I've turned my heater up to try and dry up the space, and hopefully lower my humidity. My dehumidifer is really quite good, and I think I'd my situation would be much worse if I didn't have it. I sat around today watching videos about "taco leaf" (the name cracked me up, but that's indeed what it looks like). And the more I watched, the more I'm convinced that the main reason for the leaf curling inwards was having the plant under a light that was too intense. While I still have some leaf curlage (is that even a word?), it's not as bad as it was, and on another plant, it's evened out already. So, all in all, things are looking better. I went and lifted the lights, as well as setting them at a lower intensity. We'll see how that works out.

In your opinion, if my leaves aren't looking more normal by the 26th of this month, do you think I should put off flipping them? Or can I go ahead? I don't believe that my plants are sick, no deficiencies or anything, just stressed from the lights being too intense and/or too close. But I don't want to do anything that might put my ability to flower successfully at risk, so if it means waiting a bit longer, I can do that. I've come this far, it's not going to hurt to wait a bit longer. However, I'm not entirely sure I'll be able to get my humidity down as low as is recommended. The only way I can see that happening is if it gets much colder. A couple weeks ago we were having some very cold weather and the humidity did get belong 60%, however, without a cold spell, I'm just not sure I can get it down below 65%. And we're having some very odd weather for the middle of October, so who knows.

 

[Newty]

The last post that you showed your plants in, they don't look bad at all!
Look pretty good to me, yeah there's some "taco" but they look healthy!
I personally wouldn't have an issue flipping them with a curl.

To much light could definitely be the cause, I'm sure the high RH is playing it's part in that also but I'm not seeing any major wilting on the leaves, little but not much.

Do your plants happen to get droopy a couple hours before lights off?

 

[ArtistZanner]

The last post that you showed your plants in, they don't look bad at all!
Look pretty good to me, yeah there's some "taco" but they look healthy!
I personally wouldn't have an issue flipping them with a curl.

To much light could definitely be the cause, I'm sure the high RH is playing it's part in that also but I'm not seeing any major wilting on the leaves, little but not much.

Do your plants happen to get droopy a couple hours before lights off?

Thank you for your lovely compliments on my plants. I just went out (it's nearly bed time) to have a look and they are looking better. The plant with the most "taco" is slowing unfurling, but the others are looking quite good.
I will have to make sure to take a look at the plants tomorrow when I get up. I honestly don't usually go out there until it's time to shut the lights off, which is early afternoon. But I will go out and have a look a couple hours previous to that and see if they look droopy. What does it mean if they do?
Also, I seen something about purple stems being a bad thing. I can see a pair of purple stems going to fan leaves on one of my plants, but the other stems on the same plant are all green. Is this something new I have to worry about?
Thank you for reassuring me about flipping the plants. If nothing drastic happens between now and the 26th, I will go ahead and flip them. There's a guy on YouTube who says he ramps his time up to 20 hours lights on, with 4 hours lights off just before he flips. He claims it shocks the plants into making flowers quicker. Have you heard anything about this, or any truth to it would you think? I've thought about doing it, but I don't want to do something just because one guy on YouTube says to do it.

 

[Newty]

I will have to make sure to take a look at the plants tomorrow when I get up. I honestly don't usually go out there until it's time to shut the lights off, which is early afternoon. But I will go out and have a look a couple hours previous to that and see if they look droopy. What does it mean if they do?

Nothing major, some say it's a sign that they are getting more light then they need to, meaning DLI or Daily Light Interval

Also, I seen something about purple stems being a bad thing. I can see a pair of purple stems going to fan leaves on one of my plants, but the other stems on the same plant are all green. Is this something new I have to worry about?

I've grown several plants that had red stems on the fan leaves, still happens to this day.
In my experience, they grow the same as plants without red stems and cause no concern.
I would only worry about it if your plant shows any stress or issues.

Thank you for reassuring me about flipping the plants. If nothing drastic happens between now and the 26th, I will go ahead and flip them. There's a guy on YouTube who says he ramps his time up to 20 hours lights on, with 4 hours lights off just before he flips. He claims it shocks the plants into making flowers quicker. Have you heard anything about this, or any truth to it would you think? I've thought about doing it, but I don't want to do something just because one guy on YouTube says to do it.

I've personally not heard of it before but there's plenty of things that I learn every day.
Maybe I'll give it a try sometime and see if there's any noticeable differences.

 

[PooToe]

These different "techniques" that I see on youtube are usually not all that valid.

When I was up in Northern California the growers told me that if you leave them in the dark for 36 hours before flip it's supposed to make the plant flower faster. Turned out to not be true once I got into a more professional setting with degreed pros I could ask questions.

You tube guy is saying that leaving your lights on for an extra 2 hours is going to shock them? I would chalk that one up to Broscience.

 

[LoveGrowingIt]

I don't have time to read the whole thread, so I just thought I would mention that high humidity can cause upward curling of the leaves. It can happen when the plant needs to transpire and can't, so it opens more stomata, which are cells on the underside of the leaves, and that pushes the edges of the leaves upward.

 

[PooToe]

I don't have time to read the whole thread, so I just thought I would mention that high humidity can cause upward curling of the leaves. It can happen when the plant needs to transpire and can't, so it opens more stomata, which are cells on the underside of the leaves, and that pushes the edges of the leaves upward.

Yes. Would you say that this would especially be true if it was a big swing like 48% one day to 78% the next?

 

[ArtistZanner]

I don't have time to read the whole thread, so I just thought I would mention that high humidity can cause upward curling of the leaves. It can happen when the plant needs to transpire and can't, so it opens more stomata, which are cells on the underside of the leaves, and that pushes the edges of the leaves upward.

Yes, I am having issues with humidity right now. We've been having some very warm days and nights, with rain, with makes for high humidity. I have a dehumidifier running 24/7 plus a heater, but I'm still battling high humidity. I have two hygrometers in the room, one says it's 73% humidity, and the other is saying 68%, they are both saying the exact same temperature.
And even though our temps have gone down slightly, they are still pretty warm, especially at night. We should be having temperatures in the high 30's-low 40's F, but instead we're more at mid 50's at night and during the day we're hitting low 60's F, which is not at all typical for this time of year. I just keep hoping the temperatures drop, so my humidity will drop. I don't want to make it really hot in there. I just came out and I felt like I was in a sauna.

@Newty I went and had a look at my plants before lights off and I didn't see any noticeable drooping.