Do plants wilt with low humidity?

[AgedMaster]

My plants are still doing the same thing i just checked my water report and my ph is 7.2 on average yet when i check the water with ph stick its saying 8.7 it was 9.4 all last grow and i had no problems after ph'ing, I used to grow haze without ph'ing feed and they grew fine in coco i think when i was using all of canna coco range my ph would of been good enough for coco i just dont get how my last grow was fine if my ph stick was wrong im going to check with something that has a neutral ph hopefully that is the problem

 

[AgedMaster]

Hello @agedmaster - Even plain coco on 12/12 will easily dry out in a day and the clay pebbles don't really hold any water and with 30% RH pretty sure that will get hot and dry super-quick
The pot is only half-filled and half of what's in there is pebbles, so that is very little coco to hold water
Pebbles obviously take up a much greater volume than perlite
That mix is really for flood n drain or drippers to keep it moist
I would let it sit in the run off so water is pulled back up as it is used up - in other words using the coco as your wick
I do it all the time, you know it's working because the surface never totally dries either

That's my opinion, hope it is food for thought

Hi pal i just brought some volvic water that has a ph of 7 and its reading 9.1 this will probably be a stupid question i think u use canna do u no how much canna lowers ph my start water is 7.2 do u think after adding everything it will be within range i will have to wait 3 days for a new ph stick

 

[Fenderbender]

Very much depends on the water.. if I use canna in my hard tap water PH hardly gets influenced and I need to us PH- to get it down, if I use it in distilled water it gets down to the 5,6-5,8 range.

As for low humidity, I grow in very low humidity, if I run my exhaust fan for a few minutes humidity in the tent is at 25%, the humidity in the tent only goes up when the plant is of a certain size and is able to evaporate a lot.
so for seedlings I have a way too low RH environment but I've never noticed any problems, I used to dome them, but lately I just put the seed in the final grow pot in the environment it's going to be in, no babying and they just grow.

 

[AgedMaster]

Very much depends on the water.. if I use canna in my hard tap water PH hardly gets influenced and I need to us PH- to get it down, if I use it in distilled water it gets down to the 5,6-5,8 range.

As for low humidity, I grow in very low humidity, if I run my exhaust fan for a few minutes humidity in the tent is at 25%, the humidity in the tent only goes up when the plant is of a certain size and is able to evaporate a lot.
so for seedlings I have a way too low RH environment but I've never noticed any problems, I used to dome them, but lately I just put the seed in the final grow pot in the environment it's going to be in, no babying and they just grow.

Thanks pal my ec is 0.6 from tap i will have to look for some ph strips until my metre arrives

 

[Roy Growin]

Hi pal i just brought some volvic water that has a ph of 7 and its reading 9.1 this will probably be a stupid question i think u use canna do u no how much canna lowers ph my start water is 7.2 do u think after adding everything it will be within range i will have to wait 3 days for a new ph stick

The nutes alone don't bring the pH down much, use a few drops of lemon juice, or vinegar at a push
Even pH 6.3 is OK, no need to overdo it

 

[SmokingWings]

[edit]
Need a strikethrough format here on 420.

Here ya go...at least I think this is what you are looking for.

OK, now back to the regularly scheduled message thread. Wish I could correct the spelling on the graphic as easily.

 

[AgedMaster]

The nutes alone don't bring the pH down much, use a few drops of lemon juice, or vinegar at a push
Even pH 6.3 is OK, no need to overdo it

Thanks pal ive only just seen your message could i use limes i have some in my kitchen

 

[kosio bosio]

I think that you should increase the dark hours to 6.
The plant looks tired.

 

[Delps8]

Here ya go...at least I think this is what you are looking for.

OK, now back to the regularly scheduled message thread. Wish I could correct the spelling on the graphic as easily.

Smokin', thank you for the opportunity to laugh at myself. That graphic so straightforward that even a programmer can follow it!

I've been writing software (Mac and Windows) for > 30 years, including 3 years at Apple, so I'm pretty familiar with graphic user interfaces. I looked at the menu bar and didn't see strikethrough there so I "assumed" it wasn't there.

Tip of the hat to you!

 

[AgedMaster]

I think that you should increase the dark hours to 6.
The plant looks tired.

Thats what im thinking low humidity and wrong ph cant be good god no's what nutes shes been taking if any i will decrease light until i get my ph stick and humidifier i have to wait 3 days for ph stick my towns trash

 

[kosio bosio]

Thats what im thinking low humidity and wrong ph cant be good god no's what nutes shes been taking if any i will decrease light until i get my ph stick and humidifier i have to wait 3 days for ph stick my towns trash

It's normal for the plants to be drooping a bit, before the lights go off.
That shows that it's their time to rest.
I used to keep the plants on for 24hrs and I've noticed that most of them get "tired" right before the 18th hour of daylight.
So that's why I decided to switch to 18/6.
I have controllers on my lamps so I keep the first 4 hours at 25% then I move to 50% and 4hrs before I turn them off I go back to 25%.
That's what I do in early veg and moms, late veg the 50% is longer.
Even outside the sunlight isn't always at 100%.
This method has been working very good for me over the years.

 

[Delps8]

Thats what im thinking low humidity and wrong ph cant be good god no's what nutes shes been taking if any i will decrease light until i get my ph stick and humidifier i have to wait 3 days for ph stick my towns trash

Seriously?

Your plant is, in human terms, is chronically malnourished. Cutting back on the amount of light your plant receives will continue to harm its growth.

 

[Delps8]

It's normal for the plants to be drooping a bit, before the lights go off.
That shows that it's their time to rest.
I used to keep the plants on for 24hrs and I've noticed that most of them get "tired" right before the 18th hour of daylight.
So that's why I decided to switch to 18/6.
I have controllers on my lamps so I keep the first 4 hours at 25% then I move to 50% and 4hrs before I turn them off I go back to 25%.
That's what I do in early veg and moms, late veg the 50% is longer.
Even outside the sunlight isn't always at 100%.
This method has been working very good for me over the years.

When you reduce the amount of light cannabis plants receive, you reduce growth. Similarly, when you increase the amount of light plants receive, you increase plant yield, plant quality, crop yield, and crop quality. This assumes, of course, that light is the limiting factor.

Per Bugbee, there is no research that indicates value in gradually increasing or decreasing light levels. Some light manufacturers are introducing that feature in their systems and I see that as a means of differentiating their product from others and, in the highly competitive marketplace of grow lighting. That's needed because grow lights are now a commodity product. There is no evidence-based reason to increase or reduce the amount of light, as if to mimic sunrise or sunset. As Bugbee says, plants "are ready to get to work" as soon as the lights go on.

Re. photoperiod - Growers refer to lights out as "the dark period" but, in plant biology, "the dark period" has nothing to do with the time when the lights are off. The "dark period" in plant biology refers to processes in the plant that are not light dependent and those processes run whether lights are on or off.

Cannabis does not need a "lights out" period to grow. You can grow cannabis for as long as you like using 24/0, or any combination of on/off, and the plant will remain in the vegetative state as long as the amount of light it receives is > 12±hours. Again Bugbee ("what with this Bugbee shit!?"), when asked about the 24/0 photoperiod, replied that a 20/4 schedule would give plants a "rest". Rather than use my interpretation, I'd urge you to watch the video, another segment which I discuss next.

IIRC, Bugbee addresses the idea of a "tired" plant in a video interview that he did with Dr. Growit on YouTube. It's one of the questions asked at the end of the video, when Growit is reading questions that viewers have asked in the comment section. Per Bugbee, there is no evidence-based reason why plant behave in that way but the operative theory is that plants are reacting to sunset and they are lowering their leaves, perhaps, in an effort to trap air so as to keep the ambient (warm) air. That is based, perhaps, on the fact that photosynthesis rates tend to increase as temperature increases.

Conversely, there is no research that indicates that leaves drooping is a reaction to excessive light. The symptoms for excess light levels are well documented, the most common one being light avoidance, which typically is done by rotating the leaf around the axis of the petiole, by the petiole elevating to a high angle, or by curling the edges of the leaf ("canoeing" or "tacoing"). In one of my grows, one cola was getting too much light (950µmols±) and it bent at a slight angle couple of inches down the cola.

Light avoidance behaviors are exhibited by the inflorescence closest to the light source. Light levels drop off very quickly so light avoidance is, generally, at the top of the plant and is tends to be very localized.

If the OP want to resolve the malnutrition issue, he should be getting the plant to the light saturation point as quickly as possible.

 

[AgedMaster]

Seriously?

Your plant is, in human terms, is chronically malnourished. Cutting back on the amount of light your plant receives will continue to harm its growth.

Hi pal ive always seen my plants sagging slightly 1 hour before lights off but not 2 and a half hours before i no its better the more light but my plants dont like it with the conditions there in i have 30% humidity and 27c temps this is what i saw online the other day

The Plant Transpiration Process
This means that in very dry air, the increased rate of transpiration can only go so high in the plant and then it begins to wilt. For example, if the air is extremely dry, but the growing medium has enough water, the plant may wilt and, unless the humidity increases, the plant could die

And i saw this also

Why does stomata close in low humidity?

In the first type, more water is lost from the guard cells than from the surrounding epidermal cells. This reduces the water potential of the guard cells in proportion to the humidity of the air and causes stomata to close as humidity is decreased

i was thinking it would be less stress on them unless someone can reassure me

 

[Delps8]

Hi pal ive always seen my plants sagging slightly 1 hour before lights off but not 2 and a half hours before i no its better the more light but my plants dont like it with the conditions there in i have 30% humidity and 27c temps this is what i saw online the other day

The Plant Transpiration Process
This means that in very dry air, the increased rate of transpiration can only go so high in the plant and then it begins to wilt. For example, if the air is extremely dry, but the growing medium has enough water, the plant may wilt and, unless the humidity increases, the plant could die

And i saw this also

Why does stomata close in low humidity?

In the first type, more water is lost from the guard cells than from the surrounding epidermal cells. This reduces the water potential of the guard cells in proportion to the humidity of the air and causes stomata to close as humidity is decreased

i was thinking it would be less stress on them unless someone can reassure me

The symptoms that you are seeing are symptoms of temperatures being too high and/or RH being too low and what you've quoted is 100% correct. There can be a variety of causes.

One reason is that gas discharge lights, MH, CMH, HID, HPS, etc., generate light in the infrared range of the spectrum (think "warming light" in a cafeteria). Another reason is that your ambient temps are too high. Bottom line, is that you're not getting too much light, you've got too much heat from the light.

Reduce ambient temperature. Increase RH. Those are what VPD is all about.

Increase airflow through to tent to draw in air from the outside, assuming that air outside the tent is cooler.

Move the heat source (the light) away from the plant. I haven't used gas discharge lights for growing so I don't know how much heat drops when you move the light further away but increase the intensity — that's the rub.

Again, there's nothing "wrong" with reducing the amount of light that your plant gets but you're seeing what happens with cannabis doesn't get much light. If the only option to harming that plant because your VPD is so far off (that's what this boils down to) is to lower the amount of PAR because of the heat generated by your gas discharge light, that makes the solution simple but it's something that I would argue should be the last step you take to resolve the issue.

To my way of thinking, I'd spend the $$ and get an LED grow light.

 

[AgedMaster]

The symptoms that you are seeing are symptoms of temperatures being too high and/or RH being too low and what you've quoted is 100% correct. There can be a variety of causes.

One reason is that gas discharge lights, MH, CMH, HID, HPS, etc., generate light in the infrared range of the spectrum (think "warming light" in a cafeteria). Another reason is that your ambient temps are too high. Bottom line, is that you're not getting too much light, you've got too much heat from the light.

Reduce ambient temperature. Increase RH. Those are what VPD is all about.

Increase airflow through to tent to draw in air from the outside, assuming that air outside the tent is cooler.

Move the heat source (the light) away from the plant. I haven't used gas discharge lights for growing so I don't know how much heat drops when you move the light further away but increase the intensity — that's the rub.

Again, there's nothing "wrong" with reducing the amount of light that your plant gets but you're seeing what happens with cannabis doesn't get much light. If the only option to harming that plant because your VPD is so far off (that's what this boils down to) is to lower the amount of PAR because of the heat generated by your gas discharge light, that makes the solution simple but it's something that I would argue should be the last step you take to resolve the issue.

To my way of thinking, I'd spend the $$ and get an LED grow light.

Hi pal i took your advise ive been sorting my tent for over a hour my rh is 49% temps 22.5c leaf temps 20.5c it says 1.08 kpa in the green i never had my intake pulling in cooler air if u look at any of my other posts i always have a intake slightly blowing on them but i removed it when they was small as the 250w hps was not keeping temps up i also moved light up a little as it was a bit close i would also get a led but im using hps for heat my temp in my kitchen is 12c i use a tube heater under pots when lights out my electric is £4.80 a day

 

[Delps8]

Hi pal i took your advise ive been sorting my tent for over a hour my rh is 49% temps 22.5c leaf temps 20.5c it says 1.08 kpa in the green i never had my intake pulling in cooler air if u look at any of my other posts i always have a intake slightly blowing on them but i removed it when they was small as the 250w hps was not keeping temps up i also moved light up a little as it was a bit close i would also get a led but im using hps for heat my temp in my kitchen is 12c i use a tube heater under pots when lights out my electric is £4.80 a day

A VPD Of 1.1 is a huge improvement. The folks at Pulse recommend 1.0 in veg and then 1.2 to 1.5 in flower so you're right near the 10 ring for VPD. Your plants will benefit from that immediately.

250w hps was not keeping temps up

Understood. Photosynthesis increases until about 30C. Attachment below is from the famous "Chandra" paper. The increase on net photosynthesis is ≈ 100% when temp goes from 20° to 25°, so it's probably well worth the ££ to bump the temp. You folks are having such a hard time with power and the cost of power, though. You have my sympathies. And it's all for naught.

would also get a led but im using hps for heat my temp in my kitchen is 12c i use a tube heater under pots when lights out my electric is £4.80 a day

The ££ adds up quickly but my impression is that you're not the only Brit going that route.

And, now that I've done the math on my grow, ouch!, that's even more than it is here in California. At £4.80 a day, that's ≈ $150.

The heater in my tent uses 217 watts and it runs 24/7. That's $2.00 per day, while my grow light is 156 watts running 21/3 or $1.10 per day for a total of about $100/month.

As much as that's "eye watering", it's cheaper than buying at the weed store, right!?

Oh, one thing you do if you need > RH and don't have a humidifier is to leave a pan of water in the tent or, if you can rig it up, hang a terrycloth towel in the tent so that the bottom of the towel is in a pan of water. Capillary action will draw up the water and the increased surface area of the terrycloth will allow it to evaporate.

And thinking of cost of grow lighting, I need to get into the tent and increase the PPFD…

 

[AgedMaster]

The plant looks a lot better now this is one hour before lights out the other is drooping a little i think its a bit to far from light i will put a little higher its also a different strain. Using lime to guess ph seems to be working and my environment change seems to be a lot better my ph stick arrives today i did order some buffer solution but my ph stick dont even have a screw to adjust god no's how they are not showing any deficiency's ive seen some terrible autos when everything is not right i think im lucky the node spacing is not the best but it could be a lot worse i also stressed them when they was smaller as i was spraying sides of pot when they was small to higher humidity but it was back spraying on to them with lights on thats why the lower leaves are yellow my pots are also trash they have a lip on the bottom but folds under weight if u look at the pots they look twisted slightly im hoping i dont get dry spots thanks for the help roy and delps very much appreciated