Humidity problem 40% - 90%

Little bit of background on me. I spent about 200 hours in the last couple months studying how to do this. I figured that makes me a slightly educated newbie. First my setup.

Feminized autoflowers
Massachusetts patient grow so it's a little cold right now.
5'x5'x7' Cheapo tent.
1000 watt MH
Cool Tube with XL wings (separate ventilation system.)
Oscillating fan
Humidifier set on 50
Flood table
Two clip on fans
Intake and outtake fans with carbon filter.
5 gal smart pots filled with Roots organic plus 25% growstones.
Center section Solo Cup sized seedling section consists of Light Warrior.
20/4 light cycle. (2am-6am dark)
Temperature control set to about 83 in the daytime and 75 at night.
Exhaust fan never comes on at night since it is too cold once the light goes off.

Only two of my first five seeds of sour diesel auto fems lived. Plus one mutant. So six days later I planted three Northern Lights and one white widow all feminized autoflowers. So of course I ended up with 6. Plus my Mutant . They are now 20 and 14 days respectively. I have a feeling that my five-by-five tent is going to get very crowded. They're extremely bushy and low to the ground. I have had some issues with having the light Too Close. I raised my light when I was getting heat stress. It's about 31 inches away now. I have not given them any nutrients yet. I watered them 3 days ago. Had issues with humidity Spike every time I've watered them.


Here's my problem. During the day I can keep the humidity right where I want it. Problem is when the lights go off. I go from 50 to 60% humidity to 90%. The large plants are very droopy in the morning . Took 9 hours today for them to perk up . My temperatures have always stayed between 65 and 83. Only 65 in the very cold of night. Should I change the night cycle to a warmer part of the day? Would that stress them a lot? Or try the 40-year old dehumidifier that I have in my cellar? Should I just bite the bullet and get a new 30-40 pint dehumidifier?

Got another newbie question.
I watered all my plants 3 days ago to about 10%-20℅ runoff with water lowered from 7.5 to 6.5 pH. Run off was ph 6.3 and 135 ppm.

Now, when I test my soil, the large plants have water about four or five inches down the smaller plants have water 3 inches or so down.

My question is , how far down can the plants reach for water? I imagine the larger plants, three weeks old, can reach much further down than the two week old plants.

Switching the night to the warm part of day is certainly a good option to decrees humidity. This doesn't stress the plants at all, just run a 24/0 cycle with the light on and you are good to go.

Personally I would use a dehumidifier - old or new as long as it works. I run one all through the dark period.

I will take the advice from both of you. I will run 24hr cycle before changing my night cycle and put a dehumidifier in. I may have to get a newer one though. The start up amps and energy cost would be much better on a newer model.

I had a humidity issue . I got a 10 dollar electric heater @ Walmart set on a timer with a thermostat . It would heat up the grow room enough to drop humidity from 80 to 50 .

ingenioustm said:

I had a humidity issue . I got a 10 dollar electric heater @ Walmart set on a timer with a thermostat . It would heat up the grow room enough to drop humidity from 80 to 50 .

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That works when the temp is too low and you raise it with dry heat. I have the opposite problem - I have to run the a/c and the dehumidifier at the same time to maintain a temp of 73 and r/h of 50%.

MickFoster said:

That works when the temp is too low and you raise it with dry heat. I have the opposite problem - I have to run the a/c and the dehumidifier at the same time to maintain a temp of 73 and r/h of 50%.

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Personally, I think people worry too much and work way to hard "managing" humidity.

nfhiggs said:

Personally, I think people worry too much and work way to hard "managing" humidity.

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True that, I don't even watch my rh in veg too much to be honest.

But also my rh stays well within the limits

Humidity is under control until I get a dehumidifier. Found out today that 4 days is too long to wait to water a 5 gal fabric pot. I'll kill these damn plants yet. 3 weeks old today and she looks pretty sickly. I'm sure she will live but that is time she could have used to grow.

Yes, 4 days is way too long. Your little girl looks healthy. 5 gallon bags? I guarantee you she's got roots all the way to the bottom. I like fabric; I think it's good to let the air in, and it's just about impossible to over-water. But the pots' breathability means that more water is transferred to the air, increasing RH, and they'll dry out faster. Keep an eye on the RH and be ready for changes. As they get bigger and transpire more and drink more, RH may become an issue again even if you have it under control now.

Water them at least once a day!

Are you going to top them at all? I hate topping my plants. I feel like a horrible person. Especially the first time or two, when they look wounded and confused for a few days. When the plant gets bigger and starts building a head of steam it's not so bad. Anyway, it's probably about time if you're gonna.

Still researching dehumidifiers. I think I'm going to go for the full 70 pint version. It should be up and running by the time all six are pot sized.

I've been told you don't really want to top autoflowers. That's why I started in 5-gallon pots too. You don't want to re pot autos.

Since this is my first attempt, I was going to let them grow and just take care of deficiencies. Today I just started with photosynthesis Plus. I have guano Bloom nutes but I'm not too sure how much and what kind of potassium I'm going to be using.

I apologize for the topping comments. Dangit, I hate giving bad advice, especially when its due to my own ignorance. I'm clueless about autos.

I bought a small 30 pint GE dehumidifer at Home Depot the other day. These things move a lot of air! If I use it I'll channel the blast of air across the plants.