Providing optimal growing and environmental conditions is very important in order to have a big and quality harvest. With light spectrum and penetration, humidity, water and nutrients, temperatures play a key role in development of your cannabis plants.
Depending on their genetics, which is connected to the strain’s original place of origin, they react differently to different environmental conditions. Some strains, like equatorial Sativas, like a strong light, mimicking the harsh Sun shining there and wet and humid environments that they’re accustomed to. Others like Afghanis and Kushes prefer somewhat colder temperatures and more airflow, again mimicking the environments that those plants are grown in their natural habitats.
If you expose the strain to a different set of conditions and different environments than they’re used to, it will affect their overall performance and will result in lesser quality – less potency, lower yields, longer flowering time and just weaker plants. Knowing what’s the best environment to provide your plants with is crucial in order to maximize your harvest and get the best out of your plants.
Extremely low or high temperatures will kill or seriously slow down your plants, so it’s important to keep your cannabis plants in and around room temperatures – between 20 and 30 C, in most cases – ideally between 22 and 27 C. Maintaining the ideal temperatures, without a lot of changes and spikes during all stages of growth will ensure that you have nice and healthy plants that will provide you with a good and potent harvest.
Whenever the plants have to deal with non ideal temperatures (and other environmental factors) they waste energy, that would usually go into plant development and new growth, and use that energy to fight and deal with the concensenquences, adjusting their grown patterns to the new environment, slowing down the overall growth and prolonging the vegetation and flowering time.
Having temperatures below 15 C will seriously slow down your plant’s growth and development, leaving them more vulnerable to mold, mildew and other issues. Temperatures lower than 20 C, in most cases, will also make it hard for your top part to receive energy that’s needed for their proper development.
Having temperature higher than 30 C will also slow down your plants growth, make them grow more lengthy and stretchy, wilting the leaves, as a result of root oxygen deprivation and heat, with less cannabinoid and terpene contents in the buds. As a result of increased transpiration, leaves will start to shrivel, wilt and loose color, looking for a way to reduce the transpiration. As a result of increased transpiration cannabis plants will use more water from their roots, intaking more nutrients – which may cause nutrient burns or PH related issues. With increased temperatures, more energy is spent on keeping the plant alive that causes them to be stunted or shocked with slowed growth.
Higher or lower temperatures will have more impact on smaller, not so developed plants while bigger, properly developed plants can handle a few days of extreme temperatures.
Indoor plants are generally more sensitive to lower temperatures than outdoor plants with Indica (dominant) strains usually liking a bit colder temperatures and humidity, and Sativa (dominant) strains enjoying a bit warmer and more humid environment.
Having wrong temperatures during vegetation will usually have less consequences than having them during the flowering. During vegetation, you can just adjust and increase your vegetation time for an extra week or two, to get your plants at the stage you want them.
During flowering, plants concentrate most of their energy at developing flowers or buds which plays a key role in your harvest quality and yield. Temperatures lower than 20 C will seriously decrease the suction force that moves sugars and energy from the roots to other plant parts, leaving your flowers without nutrients and your bottom parts, especially roots, in serious overload.
Both lower and higher, extreme temperatures will slow your overall growth, buds and bud sites included, which means you’ll end up with less buds that are smaller in size and have lower cannabinoid and terpene content. High temperatures will cause your buds to become thin and lengthy, make them loose color, potency, flavour and aroma.
Like we said earlier, cannabis plants feel most comfortable at room temperatures and slightly warmer environments. During various stages of plant development, cannabis plants like slightly different temperatures that come naturally outdoors, by changing of the seasons. Mimicking those changes indoors will ensure the best growing conditions.
Optimal temperatures in vegetation should be around 25-28 C during the “lights on” and around 18-22 C during the “lights off” phase. During flowering, temperatures should be 2-3 degrees Celsius lower in both phases. Lowering the night temperature in the final few weeks of flowering by a few degrees more, often helps strains to express their colors better and may result in blue, purple or pink colored leaves and buds. Slightly higher night temperatures will cause slower growth of your plants and you can use that to your advantage, manipulating the temperatures in order to keep your plants height and size in check when plants start to stretch or grow too big.
Different strains and even different phenotypes like slightly different environments. Usually, their optimal growing conditions look like the conditions of the regions where they originated from – Sativas liking hot and humid environments more and Indicas enjoying dry and colder climates more.
By introducing CO2 to the environment at 1500 PPM, your plants could withhold higher temperatures ranging up to 35 C without suffering any stress, but like with anything else, keep an eye of your plants, don’t overdo it and take it slowly until you find the “sweet spot” for your strain and setup.
To measure the temperatures we use thermometers, usually paired with a humidity meter. Depending on the size of your grow area, to keep the temperatures in check, growers use AC, heaters, coolers, vents and fans. In bigger grows, AC controls the temperature and humidity and is connected to sensors that constantly send environmental data in order for it to cool or warm the environment and adjust the humidity accordingly.
Cannabis plants, unlike humans, don’t control their temperature on their own, rather depend on other environmental factors to keep it at optimal levels. Humidity and temperature are closely linked but if you can keep your environment at optimal humidity levels and even decrease it a bit, many plants will find higher temperatures much more tolerable and easier to handle.
Besides lowering the temperature of the entire environment by using AC or coolers, changing the light setup is a good way to lower the temperatures. Different light types emit different types of energy and some heat up the environment more than others. Standard HPS/MH/CFL lights warm up a lot and if you change them to a HID or a LED setup you will lower the temperatures while keeping the light levels at the same or similar level.
Putting weaker/smaller lights or placing the lights in air tubes will ensure that less heat is emitted from the lights and that the hot air is removed from the grow area. Adding additional or more powerful intake and outtake fans will ensure for better air circulation and lower temperatures even further.
By putting your “lights on” phase during the night, when the temperatures are lower, you should be able to decrease the temperatures in the entire grow environment for a few degrees but keep an eye for the “lights off” phase temperatures, as they might increase.
If your light ballasts are located in the grow room/area, you can place them outside, as they tend to heat up quickly.
To increase the temperatures in the grow area, growers usually use either AC or place heaters around the plants. When using heaters (or coolers) make sure they aren’t blowing directly on your plants. Other ways of increasing the heat include the opposite of things described in the previous section – placing more powerful/bigger lights, adding different types of light or changing the light types and decreasing the air circulation by lowering the intake and outtake of air.
Placing a few additional CFL or MH/HPS bulbs in your grow area will both increase the light energy your plants are getting and increase the temperatures in the grow area. By placing them below the main canopy level, growers assure that additional light goes to buds and bud sites that would otherwise stay smaller in size because of the limited light they were getting, increasing the yield and potency of your harvest.
By putting your “lights on” phase during the day, when temperatures are warmer, should increase the overall growing environment temperature. Using better or additional insulation around your grow area will greatly decrease the temperature loss and help increase and stabilize your grow area temperatures. Keeping your root temperatures at around ~27 C enables your plants to withstand lower temperatures better, so placing a heating mat would be a good solution for smaller grows.
Remember: It is illegal to germinate cannabis seeds in many countries including the UK. It is our duty to inform you of this fact and to urge you to obey all of your local laws to the letter. The Vault only ever sells or sends out seeds for souvenir, collection or novelty purposes.
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