Growing Marijuana Outdoors, Indoors & Indoor-Outdoor in Hot Weather

Are you growing marijuana this summer? If not, I understand why. Summer is my least favorite time to grow marijuana.

Indoors or outdoors where I live, it’s a time of searing heat, extremely high humidity, lots of cannabis pests and diseases.

Growing indoors in hot months creates ridiculously high air conditioning costs, and unless you’re running a sealed grow room, it’s a miracle if you can get to harvest without experiencing problems such as mites, aphids, thrips, gray mold or powdery mildew.

Outdoor marijuana growing gives you a different, but overlapping set of problems.

However, some of us grow marijuana year-round. I’m doing it this year (the article was first published in 2020) because the COVID pandemic and America’s political and economic meltdown has skyrocketed demand for my buds.

I finished my winter/spring indoor season with several pounds of fine bud from several different strains—enough to take the summer and early fall off from growing.

But the COVID pandemic changed everything. Just like everybody panicked and bought up all the toilet paper and disinfectants, panic buying gave me the opportunity to sell all my cannabis except my personal stash for way higher prices than I could ever have charged before.

I warned my customers that I wouldn’t have a new harvest until next winter, but they used more weed than ever before. They said it helped them ward off COVID pandemic depression and stress.

Pretty soon, they were calling me up saying they were running out. Some of them are medical marijuana patients who only get relief from the specific strains I’ve bred and grow for their conditions. One of them broke down crying when I said I was sold out of weed.

You can see why I felt obligated to do a summer crop. As I considered the challenges I was facing and what to do about them, I decided to share hot-weather marijuana growing strategies with you…

Indoor Marijuana Growing Hot Weather Strategies

• Have your grow lights on during the coolest time of each day. This means at night, and in the early morning hours. The hottest times of the day are from noon until 7:30 pm in most places. Those should be part of your lights-off hours.
• Switch to LED grow lights; stop using HID grow lights. HID grow lights are dinosaurs. They’re crude beasts whose bulbs can’t be properly tuned for plants, and they convert a lot of the electricity you’re paying for to heat instead of to light radiation that fuels photosynthesis. The extra air conditioning capacity needed, and extra cost of cooling your grow room in summer, are just too high to justify using high intensity discharge grow lights.
• Chill your nutrients water to 68-70°F. This is a smart strategy whether you’re growing indoors or outdoors. Plants suffering from heat stress suffer less when you cool their roots this way.
• Be extra careful in monitoring your plants for grow light burn. With LEDs, grow light burn doesn’t come from excess heat as much as it comes from excess photon flux intensity and overloading the plants with too much light per light cycle. Check out this article about a grow light expert, and the videos embedded in it, to get lots of useful wisdom about the amount of light to give your plants per minute and overall per each lights-on period.
• Add C02 to your cannabis grow room air during lights-on period. Adding C02 has multiple benefits including increased growth rate, resin production and harvest weight. It also allows you to operate your grow room at temperatures several degrees above optimum for a non-C02 enriched grow room.
• In a properly-tuned indoor grow op with C02 added to create 1000 parts per million C02, grow room temperatures can be as high as 83-84°F without damaging your plants. Without added C02, grow room lights-on temperatures should not exceed 76-77°F.
• Try to have your lights-off temperatures at least 3-5 degrees cooler than lights-on temperature, especially if you’re growing Kush or Indica strains. This creates tighter, larger buds with more resins.
• Be sure to have an adequate number of high-capacity aeration fans blowing on your plants.
• If you aren’t adding C02 to your grow room air and your home and grow room are sealed up, your plants can use up the existing C02 in your air.
• It’s a good idea to have an exhaust fan in your grow room, and at the coolest time of the day or night, exhaust the room and draw fresh air in from outdoors unless outdoor temps are too hot. This might spike humidity and temperature, and may bring microscopic pests or pathogens into your room, but you need to ensure that stale air leaves your grow house and fresh air enters your home and grow op on a regular basis, unless you’re running a totally sealed grow room with added C02.
• Use high-efficiency professional dehumidifiers. You must use dehumidification in a sealed grow, but most portable dehumidifiers create tons of heat and waste lots of electricity. The most reliable company in the grow op dehumidifier industry is Quest, by far.

Growing Marijuana Outdoors in Hot Weather

• Before you start an outdoor marijuana garden, look all around your outdoor space and up in the sky above it and ask yourself: who could see my plants, especially when they’re more than six feet tall. Some outdoor marijuana plants grow to ten feet tall or taller. Do you have security on all sides, and from the air, so nobody can see your plants?
• Pay attention to helicopter and small plane overflights, especially police helicopters. If you don’t have tall fences, blocked lines of sight, no nosy or hostile neighbors, and no police helicopters overhead, don’t risk growing marijuana outdoors.
• Even in legalized marijuana states, it’s not worth the security risks of growing marijuana outdoors if there’s a strong likelihood your plants will be seen by others.
• Use white plastic grow bags or light-colored cloth grow pots instead of darker colors. Less heat on the roots, and with the cloth grow pots, more aeration.
• Cool your water to 68-70°F before watering your outdoor marijuana plants.
• Consider trenching or otherwise excavating so your plants’ roots/containers are all or part below-ground, shielded from direct sun.
• Use a mist system to cool foliage during peak sun.
• Your established plants need at least seven hours of direct sun between the hours of 10 am-5 pm every day to get enough photons for fully robust growth.
• Grow autoflowering plants and short-season photoperiod plants. Ask seed breeders which of their strains are best for outdoors and hot weather.
• Newly-germinated seedlings and plants younger than two weeks old should be placed in partial shade (including shadecloth or greenhouse), until they have enough root system and leaf mass to handle full sun.
• Use foliar spraying of beneficial microbes to protect plants from molds and mildews, but don’t do foliar spraying after early bloom phase because it adds too much humidity to buds, leading to gray mold.
• Note that foliar spraying too late in bloom phase leaves contaminants on your buds that can compromise their taste and safety, regardless of gray mold risk.
• Use foliar spraying of armoring and nutritional materials such as potassium silicate, synthetic base nutrients, seaweed extracts and natural hormonal bud hardeners. Foliar sprays should be at 5.7 pH and no more than 200 parts per million. Best time to spray is before dawn, or at dusk.
• Chill your foliar spray to 70°F. Use only reverse osmosis water when you’re making foliar sprays, not regular tap water or well water. Be sure to use a surfactant (you can easily buy yucca and saponin surfactant made for horticultural uses) to facilitate materials transfer into your leaves.
• Foliar spraying is especially useful when you’re growing in areas that don’t get much rain and/or where the air is dirty and dusty. It’s a bath for your cannabis leaves that helps them breathe easier. Spray until the leaves drip water.
• Trim and top early for bulkier, shorter, wider, sturdier plants. If you’re growing outdoor monster plants, build trellises and cages into the growth structure so your plants are supported as they mature and branches won’t break from heavy buds. Check out the videos in this article to see how that’s done.
• Some growers prefer to grow in movable pots that don’t weigh so much that it’s too hard to move them. Or they get plant dollies so they can easily move plants around, especially to put them under cover when bad weather or other hazards come.
• Use organic soils, fertilizers and other natural materials. The outdoor root zone is usually much larger than what you have indoors, and if you build and install great soil, you won’t have to use much if any added nutrients when you’re watering your plants.

Indoor-Outdoor Marijuana Growing

The sun and wind are free, but electricity for grow lights, air conditioning and fans is definitely not. Running an indoor-outdoor grow op has multiple benefits, including saving on electricity costs.

You don’t have to do it only in warmer months–some growers purchase a greenhouse or glasshouse to take advantage of sunlight and cool temperatures when they’re available.

Any time you can grow your plants with sun instead of electricity, you save money.

The way I manage my indoor-outdoor grow is to put my plants outside in full sun during peak sun hours, then back inside for their remaining allotment of light needed during that 24-hour period.

In hot months, I run my grow lights all night starting around 8 pm. In the morning, I transfer the plants outdoors. I bring them back inside around 3-4 pm, and give them at least 4-5 hours of darkness.

By running your grow lights at night and taking advantage of sunlight during the day, you greatly reduce marijuana growing costs. If your daylight durations are at least twelve hours and your plants are getting at least seven hours of direct light during the middle of the day, you could use only sunlight during bloom phase.

During grow phase, you use as much daylight as you can get, and then use grow lights to provide the balance needed to get to 18 hours of light per day.

And remember, if you’re growing autoflowering marijuana, they can handle 24 hours of light per day, and there’s no worries about light leaks or street lights or any of the other bloom phase light-triggering that can happen with photoperiod cannabis.

Depending on the time of year and your location, the sun hours seriously boost your growth rate, plant health and yield. It forces your plants to be resilient because outdoor conditions can be brutal, especially when sun is hitting directly on plant pots, stressing the roots. And sunlight is the best light for plants.

If you choose the right cannabis strains and time your indoor-outdoor grow properly, you may be able to leave your plants outdoors full-time during late summer and autumn, as long as your plants get at least seven hours of direct sun per day and aren’t getting too much rain.

If you try to finish bloom phase for photoperiod outdoor marijuana plants, beware of light pollution. Streetlights are high intensity discharge lights, and I’ve seen a streetlight 40 yards away from plants interfere with floral triggering and bud growth because it creates light pollution during the 12-hour dark cycle the plants need.

Cannabis plants are very sensitive to light cycle interruption, even by the tiniest amount of extraneous light.

Yes, an indoor-outdoor grow creates risk of insects and diseases getting on your outdoor marijuana plants and vectoring into your grow op when you bring the plants indoors.

I routinely spray my plants with safe, effective natural pest and fungi control sprays made by Sierra Natural Science.

And after I finish an indoor-outdoor grow, I bomb my entire grow house with pyrethrum foggers and treat the house and grow op with my CleanLight UV-C device that kills molds and mildews before I start an indoor season.

In general, anything you can do to reduce energy usage and costs is useful when you’re growing cannabis.

Indoor marijuana grow rooms are a major electricity consumption sector, and almost all electricity is generated using fossil fuels, dams, natural gas, nuclear, and other methods that create pollution and other environmental harms.

Even solar panels and windmills harm the environment during their manufacturing and use. Check out the Michael Moore movie Planet of the Humans, which exposes the lie that there’s a “sustainable” 100% environmentally safe way to generate electricity. Solar and windmills are NOT harmless, just less harmful than fossil fuels.

Reducing electricity consumption can include planting shade trees to block sun from hitting your grow house, installing solar panels, using LED grow lights, getting the most energy-efficient air conditioning units, upgrading your house insulation, and other tactics.

Outdoor marijuana growing saves you money and gives you the ability to grow marijuana trees that yield kilos of dried bud per plant.

Now that you’ve read this article and watched the videos, you know how and why to do it.

Have a great outdoor season!