Growing Cannabis in Extreme Hot, Cold or Humid Climates

Growing Cannabis in Extreme Climates
November 23, 2020

Marijuana plants today obtained from reputable sources are resilient and tolerant of abrupt changes in the weather. That does not mean they would tolerate extreme heat or cold. In either condition, humidity is also a problem. Fortunately, there are measures you could take to help the plants survive tough times and still produce sizable yields.

Hot and Dry Climate

Your plants thrive best when grown in temperatures that are comfortable for them. Indoors, that is not difficult to maintain as you have absolute control over the atmospheric conditions. Outdoors, on the other hand, is another matter. Depending on the location and climate, you and the plants are at the mercy of the elements. Regardless of where you grow the plants, trouble looms if you reach and exceed 85°F.

Aware that you are embarking on growing marijuana in a place that is hot and dry, consider strains that are resistant to heat. Sour Diesel and Amnesia Haze are two examples of cultivars that tolerate warm temperatures. Generally, Sativa species are better suited compared to Indica strains that are more accustomed to cold environments.

What Happens When It Gets Excessively Hot?

Indoors or outdoors, the heat needs managing. One of the earliest issues you face is the frequency of watering. You would have to increase it as moisture evaporating from the soil would occur at a high rate. Allow the temperature to continue rising; one or more of these problems may occur. Even if the plants were to go on to reach harvest, you could expect the yields to be mediocre. Worse, the buds would be lacking in aroma and potency.

Heat Stress. Above 85°F, the plants are approaching dangerous territory. At the very least, you would see the leaves curling up or cupping. The lack of intervention to lower the temperature would then cause drooping or wilting. It would not take long before growth becomes stunted.

Burnt Roots. The faster evaporation rate in places where it is hot and dry leads to hard and cracked soil. Ignore, do nothing, and the heat might start to burn the roots.

Pest infestation. Spider Mites, in particular, are much more devastating in hot climates. These pests can reproduce twice as fast under warm environments.

Hermaphroditism. Some seeds may have weak genetics or predisposed to turning into hermaphrodites. An excessive buildup of heat also causes stress, which may trigger the female plants into growing pollen sacs, getting ready to reproduce.

Blights. Hot conditions are conducive to the incubation and proliferation of bacterias and viruses. Once these pathogens start reproducing, they lead to blights and other illnesses that stunts the growth of your marijuana plants.

Root Rot. Warm temperatures cause water to hold less oxygen. Consequently, Anaerobic bacteria and fungi can attack the already weakened roots, leading to root rot.

How to Lower the Temperature?

Hot and dry climates equate to a lack of moisture in the soil and dehydration. So, the logical thing to do is to provide water, and you would do it more frequently. Remember to water the plants early in the day (or before turning on the grow lights) when it is not too hot. Avoid wetting the leaves as droplets can amplify the intensity of light, causing a burn.

Unlike indoors, you cannot lower the temperature outdoors. What you can do, instead, is to circumvent the blazing sun. If you have the marijuana plants in a container, then simply move them to shaded areas. However, if that is not possible, make wooden fences around the plants and put a mesh or cloth. A mesh screen around your plants also acts as a barrier, preventing pests from infesting the cannabis plants and wreaking havoc while also providing adequate air circulation.

Keeping the soil wet also serves another purpose – that is, to ensure the root zone does not get too hot as to damage the roots. Apart from watering, another thing you can do is to craft a humidity tray. All you need to do, if you are container planting, is to put the pots on top of a shallow tray filled with pebbles and water. As the pool of water evaporates, the moisture around the plants helps lower the temperature.

Consider using coco coir as it is more suitable for hot environments, more so than soil. Coco is a versatile medium that you can use to amend potting mixes. Alternatively, you can create a 30/60 perlite/soil mix. The loose structure of this substrate makes for better drainage and aeration. Because water can flow freely, it helps keep the temperature of the root zone under control.

What Are the Other Ways of Lowering Temperature?

Boosting your plants’ immune system is another way to ward off the ill-effects of hot climates. Humic Acid supplementation helps fight stress due to the lack of water. You can also throw in kelp extract, which mitigates the effects of heat stress. Providing a little bit of Silica goes a long way in strengthening cell walls, which helps increase tolerance to heat and other forms of stress.

Cold Weather

As a general rule, you should start harvesting before frost sets in, or else you could lose those precious buds. What if you are to grow marijuana in places where the climate is naturally cold? The first thing that comes to mind is low potency and yields. There are, however, ways to manage the environment, making it conducive to booming growth.

Should You Grow Indoors?

That is the most logical choice – growing indoors – when in a place where the climate is cold. Naturally, you would have to shell out money to buy the necessary equipment and set up the grow room. Notwithstanding the cost, you could grow marijuana at any time of the year, anywhere, as you would have absolute control over the atmospheric conditions.

As a general rule, you want to keep the daytime temperature between 75-86°F (24-30°C), and nighttime around 64-72°F (18-22°C). What you should be concerned about is making sure that the difference between the day and night cycles is within a reasonable limit. If the discrepancy is too high – exceeding 18°F (10°C) – it will affect your plants’ growth rate. During the flowering period, for example, a significant variance during the first 2 to 3 weeks results in widely-spaced internodes. Maintaining the discrepancy between 3.5-7.0°F (2-4°C) keeps the gap between nodes ideal.

In places where the outside temperature is freezing, there is one trick to manage the discrepancy. Turn on the HID lights during evenings and off during daytimes.

If your HID lights cannot emit enough heat to maintain the ideal growing temperature, you could use an electric heater or central heating to compensate.

What Do You Do When a Cold Spell Looms?

If, for some reason, you could not harvest on time before it gets too cold, there are things you can do to protect the plants. For one, you could bring them inside the house temporarily. However, if that is not possible, here are other ways:

Passive heater. Fill some dark-colored containers with water. Place them under the sun during the day so they “heat up”. In the evening, put them close to the plants while they radiate heat.

Temporary greenhouse. You could build one using wood to act as a frame and then cover with plastic to trap heat (greenhouse effect). Optionally, you can also use polyethylene or high thread count bed sheets to wrap individual plants.

Propane-powered patio heater. One other benefit, apart from providing warmth, is that the burning gas produces carbon dioxide. During the daytime, CO2 in the air around the plants promotes growth.

Humid Climates

Temperature and humidity are related. As you deal with hot or cold conditions, you should also make sure that the moisture level around the plants is within the optimal range, suitable for their growth stage. One problem you might encounter if it is excessively high is the growth of molds during cold, rainy days. For outdoor grows, if you cannot control the humidity level, you should consider moving them inside the house.

Avoiding Extreme Weather Conditions

Anytime you have to deal with temperature, you also have to deal with humid conditions. Ideally, you would grow marijuana in places where the atmospheric conditions are suitable. That is not always the case as weather patterns are unpredictable. At any rate, there are measures you can take. For peace of mind, you would grow the plants indoors if the outdoor environment is not ideal. Nonetheless, you can mitigate the harsh environment by following some of the tips provided here.