When summer arrives, some indoor marijuana growers look at the cost and work of cooling their indoor marijuana grow rooms, and decide to stop growing until the hot weather is gone.
Some of you transfer your grow efforts to outdoor marijuana growing, often at remote sites.
But many of us look at our hydroponics grow rooms sitting dark and empty, and realize we have marijuana gardening space and equipment all set up and ready for plants, but we’re doing nothing with it.
This seems like a waste of capacity.
We could grow an entire crop cycle from May to September indoors, but the heat problems seem too big to overcome.
Obvious solutions include installing cooled lights, higher-capacity exhaust and air conditioning, and other engineering fixes that probably cost money.
You can do a cost-benefit analysis to determine if it’s worth it to do whatever you need to do to make summer growing work.
For example, I had a 500 square foot grow room to cool, so I bought a portable air conditioner with 13,000 BTUs of cooling capacity.
It cost $550 and the only hassle was I had to vent it, which meant tearing up a window and making an ugly patch job.
I probably would have been better off cutting a wall vent hole for the AC, or feeding the air conditioning exhaust directly into my house’s existing exhaust system.
I spent an extra $100 a month on average keeping the room cool during the summer months. I harvested 4 pounds of excellent marijuana worth $8,000.
If I had shut down my grow op, I would have harvested nothing.
So was it worth it for me to buy, install, and operate a portable air conditioner so I could do summer indoor marijuana growing? Yes!
Here are some other ideas for how to keep growing marijuana indoors during the warm months.
The first thing to remember is your indoor grow op probably already has a system for removing heat and keeping your room within optimum temperature range.
Many of us fight heat year-round, especially if we use HID (high intensity discharge) lights, which are still the only lights that generate enough intensity to give you a high-yielding bloom phase with full-size marijuana plants.
Without added carbon dioxide (C02) in your grow room, your plants don’t like temperatures higher than 74ºF. If your grow room temps routinely get higher than that, the heat negatively affects photosynthesis, metabolism, and transpiration.
Many marijuana growers take advantage of high indoor grow room temperatures by adding C02 to their indoor marijuana grow room.
Extra CO2 helps your plants rev their metabolism to handle extra heat, but growers benefit when they do more than simply add CO2.
You can also armor plants against heat stress while feeding them what they need to make the extra CO2 and higher temperatures produce a growth and yield advantage.
Read this article for detailed information about adding C02 to your garden, and what to add along with the added C02 so you get faster growth and bigger yields.
The main thing to remember is that if you have vent fans, venting, air conditioning, and other climate control features, it’s likely you can increase the capacity of that existing equipment to keep your indoor marijuana garden within the temperature range cannabis loves.
I’ve visited many marijuana grow rooms and heard growers complain about high temperatures, especially in the afternoon.
I take a look around their home, and often see that the grow room has an outside wall that faces west, so afternoon sun beats down on the wall. If the wall is poorly built and barely insulated (as most home walls are in America), sun heat transfers into the grow room.
In general, you want to weatherproof your grow room by doing everything possible to isolate the inside of the building from the outside temperature and solar radiation.
You want to move the grow room to another location (the lower in the house the better—the basement is a great choice), so that sun doesn’t hit any walls where the grow room is located.
Plant leafy trees or shrubs to provide shade for your dwelling. Paint the exterior walls white.
Open up the marijuana grow room walls from the inside and put in higher-grade thermal insulation, perhaps installing thermal and infrared isolators on interior grow room walls.
The same kinds of interventions work if your grow room is in a dwelling with a poorly insulated attic or a very dark roof.
Most homes have insufficient attic and wall insulation. Retrofitting to increase insulation pays for itself in lower energy costs.
And if you use infrared blocking insulation, you can also reduce the possibility that police or rippers will use FLIR (heat radar) or RFI (radio frequency interference) to detect your marijuana grow room.
Time your grow light cycles to coincide with outside temperatures. Instead of having your lights on when it’s sunny and hot, have as much of your lights-on cycle as possible occur after the sun has set and before it rises.
Monitor the hottest outdoor temperatures on an hourly basis, and have your lights go off during those times.
This isn’t the same as keeping your lights off any time the sun’s up.
Instead, it means having manual or automatic control so when inside temperatures rise above a certain level, your lights shut off.
Of course, you can also use hydroponics climate controllers that activate your heat control ventilation and air conditioning whenever temperatures go too high.
You can also put some non-HID lighting (such as T5, plasma, LED, or induction) into your marijuana grow room, and have only the HID lights shut off when temperatures are at their warmest.
Any form of electrical lighting generates heat, so turning off the HIDs and/or using alternative, lower-heat lighting) isn’t a miracle fix, but it does lower the heat load.
And remember this marijuana fact: you can get away with using no HID during veg phase, but during bloom phase, you really do need HID if you’re going to get your full THC and weight potential.
Yes, you can get decent harvests using a non-HID setup, especially in closet and chamber grows.
But I’ve looked at nearly a dozen different brands of LED lights used in grow rooms, and there are still many problems with LEDs that have discouraged professional growers from adopting them for full-size marijuana grow rooms.
Here’s my challenge: If you’re a hydroponics LED manufacturer and you believe your technology will give me yields and THC as good as my HID gives me, send me one of your LED units so I can test it against my metal halide and high pressure sodium bulbs..
Which LED manufacturer has enough confidence in its products to take me up on my challenge?
So far, none. I’ve repeatedly asked LED manufacturers to pony up and put their LED to the test in my marijuana garden, and none of them have done it.
Yet I see their advertisements making lots of fancy claims, and it’s troubling to see the marijuana growing community getting scammed.
There are several easy-to-use supplements that protect your marijuana plants against heat stress. Many of these also increase plant metabolism to make use of CO2 augmentation and spur overall plant vigor and productivity.
I use a hydroponics potassium silicate booster because silica is a major component of your plants’ physical structure and is often in short supply in hydroponics marijuana gardens.
Even in soil-based gardening, marijuana plants benefit from a silica additive that you start feeding when your seedlings or clones have well-established roots. You continue that all the way through bloom phase.
Other benefits are that potassium silicate boosts floral production, aids in the formation of resin glands, and makes your plants’ leaves, stems, and flowers better able to resist biting/sucking insects, and heat.
You can also feed a vitamin B hydroponics formula that helps marijuana plants deal with stress while also increasing plants’ ability to intake and utilize nutrients for faster growth and larger, higher value yields.
When I say “B complex,” I’m referring to a complete formula that has folic acid, B5, thiamine, B2, B7, niacin, and other B vitamins that assist with virtually all plant functions.
When you give a properly designed B complex to your marijuana plants, you help them deal with heat, cold, drought, intense light, accelerated metabolism, and other stress factors that can limit growth and yield.
Nature intended marijuana roots to grow underground, where temperatures are significantly lower than aboveground. When marijuana root zones or nutrients water exceeds 72ºF, various problems can arise.
These include harmful microbes and/or algae in hydroponics reservoirs, or harmful pathogens in root zones. Roots struggle to function and stay healthy because they are too warm to properly function.
The warmer your hydroponics nutrients water temperature, the less oxygen it holds—and your plants do absorb oxygen through their roots via water.
Some growers decrease root zone temperature by adding ice cubes or ice water to their nutrients reservoir, or using a chiller. Or they manipulate grow room air exchange and circulation to ensure that the root zone is in the range of 68-72ºF
You also help marijuana roots by providing beneficial microbes to your root zone, so roots are armored and enhanced by a symbiotic network of microbes, fungi, and increased root mass that makes your roots more likely to thrive in higher than optimum temperatures.
There are many grow shop formulas that claim to contain beneficial bacteria or fungi. Some of these formulas are powdered; others are granular, or liquid. My favorites include Great White, Mykos Extreme, Voodoo Juice, and Piranha.
Add carbohydrates such as molasses or Bud Candy that feed beneficial microbes.
The carbs are also absorbed via roots to help your marijuana plants have more energy, especially during bloom phase when plants have a harder time keeping up with energy demands.
Please remember: you can add a chiller to your hydroponics reservoir system, or otherwise adjust the temperature of your hydroponics nutrients water to keep your marijuana root zone within its ideal temperature range.
Some marijuana strains are better-suited for warm growing conditions than others. Look for a future article that describes some of those strains.
As for the decision whether to keep growing marijuana indoors from April to September, only you know exactly how much money and hassle it can cost you to keep your marijuana grow room going all summer.
Unless I have summer vacation plans that could take me away from my grow house, I’ve found it’s worth it to beat summer heat and do an indoor marijuana grow in summer. I time it so my harvest comes before outdoor harvests, so I have fresh bud before everybody else does. Stay cool, and enjoy your indoor marijuana summer growing!