[slownickel]

Pushing RH up is not that hard to do.

What folk don't realize is that PM is not caused by high RH. It is caused by the swing in the RH. More than a 15% swing on most varieties is the kiss of death and all kinds of disease will show up, especially if the plant had bad nutrition. Getting Ca uptake is everything in agriculture.

Doka knows the importance of Ca, having this plant in a stressed situation due to low RH is not good.

The situation needs to be evaluated a bit more.

Why is the RH that low to begin with? What if any equipment do you have available?

Pans of water on the floor could help, but I would be worried about the peaks and valleys of RH first....

[slownickel]

Originally Posted by Chrono2

for starters id like to say about 25-28 days in, my plants look healthy and are on par size wise with other day by day grow videos of auto flowers. (especially considering this is my first grow ever)

now for the main question can i veg and flower in 45% Rh? has anyone had SUCCESSFULL grows in these ranges give me any input? 43-50% RH is the average for my tents (lights on, and about 50-60 lights off) and tbh i dont want to add a humidifier or dehumidifier if i dont HAVE to, but everyone reccomends my rh be alot higher in veg :\

The key is the swing. If you are at 45 and regularly hitting 60 RH, you are at the threshold of PM or some other rot. If you can raise that 45 to say 55 and then push the upper to say 65 or so, that would probably help.

Your RH is not impossible to work with. It is just that your plants would be a lot happier (scientific term) at a higher RH. Just be careful what you wish for.

More than 15% RH swing is asking for problems. Lots of literature out there that proves this. Lot of literature also blames high RH for PM and is dead wrong. Even in the scientific world there is a lot of garbage information.

[PaulieWaulie]

Originally Posted by Chrono2

Thx for the reply mate seems i might be just worrying over nothing, think ima buy a humidity controller and see how that works maybe save some electricity and get better yields

There is definitely a sweet spot for VPD with your temp and humidity. But I think unless every aspect is dialed in on your grow, your not gonna see that benefit too much compared other issues you could focus on if your just beginning.

[PaulieWaulie]

Originally Posted by slownickel

Pushing RH up is not that hard to do.

What folk don't realize is that PM is not caused by high RH. It is caused by the swing in the RH. More than a 15% swing on most varieties is the kiss of death and all kinds of disease will show up, especially if the plant had bad nutrition. Getting Ca uptake is everything in agriculture.

Doka knows the importance of Ca, having this plant in a stressed situation due to low RH is not good.

The situation needs to be evaluated a bit more.

Why is the RH that low to begin with? What if any equipment do you have available?



Pans of water on the floor could help, but I would be worried about the peaks and valleys of RH first....

Both times that I have gotten PM my Lights off Humdidity has hit 60s RH. I would say lights on it was 50%. So a swing of only 10. Which would seem pretty common considering the temp change of 10 degrees C being common.

Why is the swing itself the culprit you think ?

[slownickel]

Originally Posted by PaulieWaulie

Both times that I have gotten PM my Lights off Humdidity has hit 60s RH. I would say lights on it was 50%. So a swing of only 10. Which would seem pretty common considering the temp change of 10 degrees C being common.

Why is the swing itself the culprit you think ?

Here is what the BASF guys compiled. They usually do a good job...

https://betterplants.basf.us/news-&-...ery-mildew.pdf

I imagine in almost all the cases, humidity spikes immediately after lights are turned off. The walls can often sweat from excess moisture and the same thing happens on the leaves. May not be running off, but most definitely highly localized humidity.

Then of course, many still do such a bad job growing the plant, induced toxicities of Mg, Fe and Al and at the same time have a lack of Ca, Cu, Zn, Mn and others.

Don't guess at humidity levels. Realize that a measuring device on the wall has little to do with the RH under canopy.

Some folks have mixes that are often anaerobic down deep and hold too much water. This also makes for weak tissue.

Then of course there is genetics. Some genetics are much weaker than others and much more susceptible. There are a bunch of factors that lend themselves to the perfect storm...

[Avenger]

Periods of high humidity and relatively low temperatures at night are prime conditions for powdery mildew conidia to germinate and form chains or threads of spores that protrude from the leaf surface and are visible. Then the lights come on and the RH tanks and drys everything out. Perfect conditions for powdery mildew dispersion. Poof, spores in the wind, ready to land and begin infecting new tissue this evening when the RH spikes again.

fuck it up enough to let the plants surface temperature reach the dew point and free water to form and you will meet downey mildew too.

But if you routinely spray fresh water on the plant you can help kill powdery mildew spores.

[Absolem]

Originally Posted by PaulieWaulie

Both times that I have gotten PM my Lights off Humdidity has hit 60s RH. I would say lights on it was 50%. So a swing of only 10. Which would seem pretty common considering the temp change of 10 degrees C being common.

Why is the swing itself the culprit you think ?

Hey Paulie,

I'd be curious what your temperature swing was from lights on/lights off when the pm reared.

Originally Posted by slownickel

What folk don't realize is that PM is not caused by high RH. It is caused by the swing in the RH. More than a 15% swing on most varieties is the kiss of death and all kinds of disease will show up, especially if the plant had bad nutrition. Getting Ca uptake is everything in agriculture.

Agree.


Cool. Just added to my post count.

[jidoka]

1st grow absolute best thing to learn is how to get Ca in the plant. Do that and the entire rest of your grow life just got easier. Don’t do that and get ready for one bro science cure after another

If you don’t want to humidify how do you feel about foliar spray?

[heatherlonglee]

Originally Posted by slownickel

Some genetics are much weaker than others and much more susceptible. There are a bunch of factors that lend themselves to the perfect storm...

OP doesn't know his strains! OP doesn't know what pm looks like! OP is on his first grow! Op has more than one tent going! OP has multiple strains running; again first time with these strains ever! Perfect storm of idiots is coming for the OP. lol

Straight knowledge here!

Originally Posted by PaulieWaulie

There is definitely a sweet spot for VPD with your temp and humidity. But I think unless every aspect is dialed in on your grow, your not gonna see that benefit too much compared other issues you could focus on if your just beginning.

[Chrono2]

thank you for all the replies everyone appreciate it!
unfortunately i dont have a few reps worth of time to practice with
got my humidity controller yesterday and am keeping the room at about 56-62 at all times right now, no more than a 7% swing (in reality its more like 3%, but as soon as my exhaust fan turns on it spikes by about 2-3%, i think thats just an odd offset of the room getting alot smaller when the fans turn on, bumping the % humidity up)

i also have 2 16" inch fans oscillating directly on the plants, canopy temperature is around 22 C