If you’ve never attempted outdoor cannabis cultivation, you might not understand why it’s worth the painstaking effort of prepping your plants for the harsh outside environment. But when you see monster plants growing the size of trees, with each one yielding a kilo or more of dried buds, you’ll swiftly understand why outdoor growing is worth it.
But it’s challenging to write succinctly about when to place your cannabis plants outside for the outdoor grow season. This is because your garden’s literal distance from the equator and, as a consequence, the length of day — commonly referred to as photoperiod — is what triggers hormonal responses in your plants.
Photoperiod and weather are two huge factors that will influence how successful your outdoor cannabis grow op will be. If you put plants outdoors too early or too late, they won’t develop properly. If you put your plants out before all chance of frost has ended for the cold-weather season, your plants could be injured or killed by the extreme cold.
Your location also greatly affects photoperiod. In the more southerly parts of the Northern Hemisphere, including the US southwest and southeast, the longest days of the year are rarely more than 14.5 hours, including dawn and twilight, when no direct sun hits your plants. By contrast, in the Pacific Northwest, Seattle’s total maximal summer day length can be 16 hours, while that of Anchorage in Alaska can be as long as 20 hours in peak summer. If you’re growing photoperiod cannabis plants outdoors, these day lengths aren’t always ideal. Photoperiod cannabis thrives with 18 hours of grow-phase light and 12 hours of light during bloom phase. If they only get 14 to 15 hours or less of light per day in grow phase, development will slow and the plants could begin flowering. The closer they get to having only 12 hours of light per day, the more likely it is that they’ll start flowering.
So, let’s say you live in the legal region of Southern California, or the black-market states of Texas or Florida, and want to grow outdoor weed this year. If you start your plants indoors and move them outside in the month of May, they’ll get about 13 hours of light per day. In that situation, what happens with many strains (especially those bred for more northerly outdoor locations), is that soon after you put them outdoors, they start flowering. Instead of gaining height like photoperiod grow-phase plants do under 18 hours of indoor light, the plants only gain their bloom-phase stretch, and often end up growing to be smaller than average. Additionally, inadequate light hours at the wrong time triggers stress responses that can cause hermaphroditism, mutations and underwhelmingly small yields of low-potency buds.
These problems aren’t quite as likely to happen when you grow autoflowering cannabis or photoperiod strains dominated by tropical sativa genetics. Breeders of autoflowering strains claim their plants do best under 18 to 20 hours of light per day, from germination to harvest. However, I’ve grown autoflowering strains outdoors that got only six to nine hours of direct light per day, while total photoperiods including dawn and dusk were only 12 to 14 hours. To my surprise, the strains started flowering automatically during weeks two and three just like they’re supposed to, creating yields and potency that breeders said were similar to what I’d have gotten with 18 to 20 hours of direct light per day.
Likewise, I had adequate, although not spectacular success when I started photoperiod feminized Kali Mist seeds from Serious Seeds grown outdoors three weeks after spring equinox, when there was only about 13 hours of total light per day in my region. All but one of the plants grew slowly but surely in vegetative phase until early September, when day length was dropping like a rock. The plants started flowering, but it took them until mid-December to be ready for harvest.
Kali Mist is one of very few pure sativa strains, but not all pure sativas are tropical in origin, and with all the hybridization present in the seed industry, you never know if indica or Kush genetics have been inserted during breeding. If you intend to grow outdoors in regions where day lengths, even at the height of summer, rarely exceed 13 to 15 hours a day, it’s best to grow pure tropical sativa. Why? Because authentic tropical strains such as the legendary Colombian Gold come from landrace genetics that grow naturally near the equator, where 12–12 outdoor light cycles happen year-round.
This isn’t to say that growing tropical sativas outdoors in southerly areas is easy. It’s not easy anywhere, because tropical sativas are more difficult to trigger into flowering; their floral development is extremely slow and often quirky; and in some cases, unless you’re able to put them into total darkness for 14 or more hours per day, they may never finish. Their buds continue to slowly develop with a few resin glands here and there, but never thicken, and the glands stay tiny and clear. I’ve grown supposedly stabilized commercial sativa strains that never ripened, even though, as an experiment, I let them go on for months. Sure, the soaring sativa high is like a mild LSD trip, but yield was woeful, and the high had no body effects whatsoever. It was all a head high.
Starting Plants To Maximize Summer Sun For Outdoor Cannabis Growing
The easiest, most foolproof practice for putting photoperiod plants outdoors is to start them indoors under 18 hours of light in mid-May so they’ve had four to five weeks in indoor grow phase by the time the summer solstice (the longest day of the year) rolls around in June. With indoor growing of strains that you intend to finish indoors, grow phase should go no longer than three to five weeks, because any longer will create massive plants that end up too wide and tall for indoors, unless your ceilings are upward of 12 feet high. Your plants may also run out of root space if you let them linger in grow phase too long.
Growing cannabis outdoors allows you to take full advantage of the boundless space available. Unless I have a reason to grow short outdoor plants due to security concerns of living in a neighborhood with high population density, I want my outdoor weed to grow to be monster plants. This means I’ll let my grow-phase plants destined for the great outdoors go far longer indoors than I would if they were indoor finishing. I put them in very large pots. I trim them to create dense branching. Then I put them outdoors on the summer solstice.
In some regions, total light per day at summer solstice, which falls this year on June 21, is 14.5 hours or less. In the Seattle area, it’s around 16 hours of light. But within a couple of months of the summer solstice, almost everywhere in North America (except for Alaska), total hours of light per day will be dropping to 12 to 14 hours per day. By that time, most strains will have started flowering and will finish by the end of November at the latest. Want to plan precisely? Head to timeanddate.com to calculate the exact sunrise, sunset, dawn, dusk and twilight durations for every day of the year in your location.
Hardening Plants For Outdoor Cannabis Growing
When discussing transitioning your cannabis plants outdoors, we must not ignore the important topic of hardening your indoor plants so that they’ll survive the move. Most indoor grow lights lack the intensity and spectrum of the sun, especially that of the spring and summer sun. I’ve had healthy seedlings happily growing indoors under 18 hours of HID or LED grow-light radiation that were severely damaged when I abruptly started putting them outdoors in full sun for even just a couple of hours a day. Their leaves turned downward, away from the sun. Some never recovered. They simply didn’t have the leaf surface or root mass to handle that much radiation.
To avoid that shock and damage, I place my seedlings under shade that comes from trees or from a shade house, which is a miniature greenhouse enclosure with material that filters sunlight enough to protect young plants that aren’t yet accustomed to sunlight. After a few days spent outdoors in shade and after the plants have at least five or more sets of true leaves, I start moving them into full direct sun for short periods of time, but not during the peak sun intensity hours of 11 a.m. to 2 p.m. Rather, I give them full sun during early morning or late afternoon, gradually getting them used to the strength of the powerful rays. Within one to four weeks using that strategy, and depending on the strain, the plants will be able to handle full and direct sunlight all day.
Hardening also means getting plants that started indoors used to the heat and humidity of the outdoors. If you’re planting directly into the ground so that your plants’ root mass is covered by soil, this is the best way to protect your roots. Plants grown in pots aboveground experience an unnatural condition of having the sun hit the roots almost directly, save for the thin layer of material the pot is made of. Black pots sitting aboveground in full sun are deadly for roots. I prefer to grow in 100- to 400-gallon white cloth pots that sit aboveground, such as these white cloth pots from Radicle. Not only are they sturdy and reliable, they’re also reusable. Cloth pots give you the added benefit of automatic root pruning and oxygenating airflow that hard-shell pots can’t provide.
Outdoor Cannabis Growing In Heat And Humidity
Now that we’ve discussed strategies to stop your root zone from frying, there’s still heat and humidity to deal with. The likes of Southern California, Arizona, Utah, Nevada and Texas have low humidity, intense sun, soil that is mostly sandy, and high temperatures. When it comes to outdoor cannabis cultivation, this is a recipe for plant disaster, unless you sufficiently water frequently enough. The low humidity can suck the life right out of the plants during temperature spikes because they can’t draw water fast enough from the root zone to stay alive — or there might not even be enough water to draw.
Conversely, in hot conditions that are also humid, the problems are the opposite. The root zone may become waterlogged if it’s been raining a lot, which decreases root function. Heavy, humid air deters leaf transpiration, which is a valuable function of the plants’ metabolic nutrient transport and photosynthesis. If you’ve done your research ahead of time and chosen strains best suited for the climate conditions of your outdoor grow, your plants have a better chance of surviving.
In some cases, if you have the infrastructure to do so (and this would unlikely be the case when it comes to a remote guerrilla-style grow), you can set up misters that cool your plants by producing chilled aerosolized fog. This approach has the added benefit of giving you the opportunity to use aerosolized natural pest control and feedants that fuel and protect your plants.
In all cases, outdoor growers should take advantage of plant armoring products such as B-52, a vitamin B complex that helps plants fight stress, and Rhino Skin, the only potassium silicate hydroponic formula made for cannabis. Rhino Skin helps plants build sturdier cell walls and resin glands. I also use the bloom booster Nirvana, which boasts a myriad of natural substances that strengthen and protect stressed plants. Using cool water to hydrate plants during the hottest weather is also a smart move.
So, in summary, the tactics for successfully transplanting indoor cannabis plants into outdoor grow ops are as follows:
- Start the plants so they’ve had sufficient grow-phase development before placing them outside near the longest day of the year, the summer solstice of June 21.
- Choose strains most suited for your outdoor climate, security conditions and photoperiod length.
- Harden plants by giving them gradual sun exposure and protected root zones.
- If possible alter the outdoor environment of your plants by using chilled mist and sufficient water in the root zone.
- Plant your roots directly into the ground or in white cloth pots so as to avoid root damage from radiant heat transferring into the root zone.
- Feed your plants B-52, Nirvana and Rhino Skin to give them nutrients they can use to fight stress and build stronger plant tissues.