Winter marijuana growing season is here, giving you a different set of opportunities and challenges compared to growing marijuana indoors during warmer months.
With indoor marijuana growing, any time of year has its challenges.
For example, I live where there are very hot summer months.
My marijuana grow room is in the back of my house, shaded by trees. One day the electric company sent a crew that trespassed on my property and chainsawed the biggest tree shading my grow room wall.
Huge amounts of sun started hitting the wall and heating up my cannabis grow room.
I was running three 1000-watt HIDs and could barely air condition and vent the heat enough to keep the room under 82F.
So I looked forward to cold weather because all that unwelcome grow room heat becomes a welcome benefit during winter marijuana growing.
With outdoor temperatures where I live averaging 15-38F most of the winter, and the rest of my house other than the grow room set to 65F, I use HID heat to warm the grow room to the ideal growing temperatures of 74F when lights are on.
If I’m using C02, I want my grow op to be about 83-84F.
You need the right venting, air exchange, and monitoring to make the best use of bulb heat during winter marijuana growing.
When lights are off, I use either the whole house heater or a localized in-room heater with a digital thermostat.
I want my grow room to be about 7-8 degrees cooler during lights-off than during lights-on.
It’s good to have your lights-off temperatures a few degrees cooler than your lights-on temperatures, but if your grow room goes below 65F, and especially if you have high humidity, you run the risk of powdery mildew or other attackers, in part because of humidity issues.
Get a dehumidifier.
Too-low temperatures slow down your marijuana plants’ metabolism, growth rate, root development, and nutrients uptake.
Remember also this general concern: electrical load.
If you add a 1500 watt space heater to the already-existing electrical load of your winter marijuana growing environment, you might blow your circuit, creating fire risk.
Always do an electrical load check and an electrical system retrofit (if a retrofit is necessary) BEFORE you set up a marijuana grow room.
When I did my first winter marijuana growing, my closed-up grow room with three HIDs was too warm.
I needed cooler air in there.
Because I live in such a way that I have no unplanned visitors or other security risks, I experimented with leaving the grow room door open a few inches during lights-on cycle.
I had two tower-shaped circulating fans, and a precision hygrometer/thermometer.
After a few days, I saw how exactly how much to open the door to mix the 65F house air with the warmer grow room air to create a consistent 73-75F, approximately 59% humidity environment in my grow room.
My winter marijuana growing door-open program worked well except it presented a vector for odor, spores, gnats, dust, and microbes if there were any present, and those could have trashed my marijuana grow room.
So I installed a high-CFM venting fan connected to a carbon filter. The venting fan was not connected to ducting or tubing that fed to the outside world.
Instead, I sent it into a duct that distributed grow room heat to the largest room in my house.
I put carbon and micronized filters on all my air intakes and outflows throughout the home. I also bought special carbon filters for my furnace.
Last year, a trusted grower friend who has HVAC (heating, air circulation, and cooling) expertise gave me a set of other ideas.
These included a better linkage to exploit my HID heat during winter, and installing whole house UV and carbon filtration, which was mediated through my furnace/AC air handler.
When I installed those new winter marijuana growing systems, the entire house atmosphere was cleaner, the grow room air was purified from floating dust, spores and other bad stuff, there was no marijuana odor.
The heat from the grow room was saving me money because instead of being shunted outdoors, it was staying inside and reducing my overall heating bills.
Another thing that cold weather did is to force me to look at my attic and wall insulation. There was no wall insulation and the attic insulation was weak, like R-20.
So I added insulation to R60 wherever I could, while also putting baffles, sealers, and a ridge vent and improved soffits to make sure my attic ventilation was just right and that I am not leaking any heating or cooling out of my home.
Winter marijuana growing gives you many rewards. Even “free” heat!
There’s often a shortage of fresh-grown cannabis buds that starts a month or two after outdoor harvest season ends, and winter growing gives you a way to have fresh buds while the snow is still on the ground.
And when you can use HID heat to reduce your home heating costs and keep your winter marijuana growing marijuana temperatures where they should be, that’s great too.