Frosty buds are nice but unfortunately we're not talking about that kind of snow. Cannabis is known for enjoying warm climates and it loves bathing in the sun. That means some difficulties can arise once winter arrives. Fortunately, with the advancement of indoor growing techniques, it is possible to grow all year round in the comfort of our own homes. We're here to show you what you need to watch out for when things get a little chilly outside.
Cannabis plants can indeed grow in winter. Whether they grow well or not is a different story. Outdoors, the cold and low light might not be enough to give high yields and the process becomes particularly difficult because unlike the indoors, we have way less control over the environment. Growing weed indoors during winter may be more of a challenge to manage but it is certainly possible.
Winters are extremely diverse and obviously some climates will be harsher than others. Depending on where you live, you may be able to get away with keeping plants outdoors for longer in the autumn.
However, most of the time the winters are just not suitable for cannabis to grow properly outside, especially if it snows or temperatures drop below freezing. There are strains that can handle slightly lower temperatures but warmth is key if you are looking to produce high quality weed.
Many growers move their practice indoors once their outdoor plants have been harvested so they can continue growing throughout winter season without too much hassle.
It takes some planning and investment, but having an indoor grow room ready for when it gets cold means you can keep happy greens. It also gives you a space to veg your plants in before next year's outdoor growing season.
If you love growing weed then having plants all year round is a no brainer. Being able to grow through winter means more harvests per year of your favourite bud. We've outlined some of the reasons why you might want to grow cannabis during winter.
There are some added benefits to setting up an indoor grow when temperatures are low. With the right setup, the heat generated by lighting and other equipment can be used to warm up the home. Even though your electricity costs are likely to go up, potentially having more bud at the end of the cycle makes the extra expense worth it.
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When temperatures decrease to 15°C and under, growth tends to slow down drastically. Once it drops below freezing, it is likely a cannabis plant will die. Aim to maintain temperatures above 18°C at all times. Between 20-25°C is often the sweet spot, just remember there are many variables like the strain or stage of the cycle. The point is, you need to monitor the temperature to make sure your plants don't get too cold or they will suffer.
The dark hours should be carefully controlled as no heat is generated by the lights during this time. Heaters may be necessary to keep temperatures above the comfortable level. These can also be setup on timers so they come on when your lights switch off.
It can be a good idea to set your lights to be on during the night when outside temperatures are coldest and have them off for the warmest parts of the day. This helps to prevent big fluctuations in temperature which may shock plants.
The sun is a cannabis plant's main source of energy and it provides plenty of light during the summer months. In winter, there is simply not enough hours of daylight to meet the demands of your plants. This is why we must provide additional light to compensate. Managing indoor lighting can be expensive, but it is one of the most important parts of the setup.
HID lamps are powerful enough to grow weed indoors during winter and have the benefit of radiating lots of heat. Using LEDs or fluorescent lights is also possible (plus they are cheaper to run) but it is recommended to install extra heating as they won't provide much warmth for your plants.
Tip: Placing seedlings on windowsills with supplemental light can be enough to keep them going in their early stages.
Maintaining the correct relative humidity (RH) can be a challenge when temperatures are low. Humidity levels often increase with low temperatures, so if you are pulling cold air from outside the RH is generally high. Depending on the stage of growth, we should try to keep the relative humidity in the grow room between 40-75%.
High humidity is usually the cause of mold, which becomes increasingly hard to control as it gets colder. Dehumidifiers can do a good job of reducing relative humidity levels but how efficiently they remove moisture from the air depends on the size of the space in question, as well as the quality of the dehumidifier.
Raising the temperature will reduce relative humidity. For example, if the fresh air coming into the grow room is 15°C with a RH of 60% and it is heated to 22.5°C, the RH will decrease to roughly 40%.
Conditions that are too dry can be controlled with a humidifier, but make sure you choose one that holds plenty of water, otherwise you might have to refill it multiple times per day.
Natural sunlight can still be used to grow in winter. Although the sun doesn't hang around for too long, it might be strong enough for a few hours to give your plants a decent dose of light. Growers that choose to grow in greenhouses have the ability to add equipment such as lights, or install blinds/covers to help them manage the light schedule.
If you cannot grow indoors and choose to continue outside, preferably set up a greenhouse.
Try to grow directly in the ground because temperatures are warmer and heat does not escape from around the roots so easily. Alternatively you can plant in pots and place them into a hole in the ground which provides added insulation, but still allows you to move pots in the event of a storm.
KratyGrow's winter grow on GrowDiaries.
When it comes to choosing the appropriate seeds, mold resistant strains or autoflowers tend to perform better under colder conditions. These are normally Indica dominant strains. Sativas orignate from warm, humid climates and suffer under cold conditions more easily than Indicas do.
Due to their Ruderalis heritage, autoflowers are ideal because they have a short cycle and mature based on their age rather than the amount of light, making them much easier to grow in winter. However, autoflowers still need plenty of light in their vegetative stage if they are to reach their full potential.
Tip: During the dark hours, outdoor plants can be covered using plastic sheeting to help them retain heat.
With all the possibilities we have to grow indoors it is definitely worth considering growing during winter. Your yields will be better, and you reduce the chance of wasting seeds or clones to cold weather and mold. On top of that, you are able to experiment with all sorts of indoor growing techniques which can help you become a better grower.
Have you grown in winter before? Share your experience with fellow growers in the comments section below!
CULTIVATION PRACTICES EFFECT CANNABIS SATIVA YIELD. - Wogiatzi-Kamwoukou, Eleni & Giannoulis, Kyriakos & Porichi, Anna & Gougoulias, Nikolaos & Kalfountzos, Dimitrios & Bilalis, D.. (2019).
Hydroponics Cultivation Cannabis sativa L. Plants. Planta Medica - PLANTA MED. - Chandra, Suman & Lata, Hemant & Khan, Imtaz & Elsohly, Mahmoud. (2010).
Physiological and biochemical features of Cannabis ruderalis in the Chui valley. Journal of Biotechnology. - Akhtaeva, Nursulu & Boribay, Elmira & Mamurova, Assem & Kiekbaeva, Lashyn & Inerbaeva, Saniya. (2014).
This article was updated October 2020.
