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Temperature

temperature is important

Plants will only thrive if they live in the correct environment for them. They receive light from either the sun or artificial lighting, which helps them to stay warm, as well as the level of evaporation and the outdoor temperature. Although you will want to keep your cannabis plant warm, you must be careful not to create an environment that is too hot, as it will cause stress to your plants. 

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the right temerpature for each grow stage

For each stage of growth, your plant will require different levels of heat. It is up to you to keep an eye on the temperature of your grow room and monitor your plants regularly.

Seedling stage

For seedlings and young clones, you should ensure the temperature is around 20 to 25 degrees Celsius and that the humidity is high (this can be helped by using a humidity dome). These warm temperatures will help the seedling to develop a good root structure.

Vegetative stage

During the early vegetative stage, you can keep the temperature at 20 to 25 degrees Celsius. Plants love a high humidity of around 70% during this time, which can be lowered further into the vegetative stage, as plant develops more. For night temperatures, as long as it does not get below 15 degrees Celsius, plants can thrive from having slightly cooler temperatures overnight.

Flowering stage

Cannabis plants in this stage will do better with a low humidity and a comfortable temperature not exceeding 28 degrees Celsius. Temperatures that are too high during this stage can greatly affect bud growth and quality.

Drying and Curing stage

Keep the humidity at around 45% and the room temperature at 18 degrees Celsius, to allow your buds to dry correctly and increase your chances of a quality end product. 

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the climate of your grow room

It is important to look at temperature and humidity at the same time, as these will both effect the overall temperature of your grow room. Cannabis plants generally evaporate 90% of the water they are given, which will then dispense into the grow room. For this reason, indoor grow rooms tend to be slightly higher in humidity than an outdoor grow.

To measure the humidity in a room, we use relative humidity (RH), which gives a percentage of the moisture that is in the air, in relation to the maximum amount of water that the air can hold at a certain temperature. The amount of water the air can hold varies with the temperature. Hot air will hold more moisture than cold air. When outside, if the RH gets to 100%, it means the air cannot hold any more water, as it is at full capacity. This will then result in clouds, rain, or fog. 

Problems with a humidity that is too high or low

Its essential that you control the humidity levels of your grow room. There are some things that will indicate the humidity to too high; these are mould or rot, white powdery mildew, nutrient burn, or slow plant growth. On the other hand, if you allow the room to get too cold (below 15 degrees Celsius) it can badly damage plant growth or even kill your plant. It is a good idea to keep the roots of your plant up from the floor in order to keep them warm.

Keeping a check on the humidity and temperature of your room will mean you can quickly adjust to give your plants the best environment.

If the humidity is too high, you can use a dehumidifier to lower the RH levels, and if the RH is too low, then a humidifier to increase humidity. A good ventilation system will also work well to disperse air evenly around the room, controlling the temperature. If the temperature is too low you can increase insulation, move plants closer to the light or get a light that emits more heat, or you could use a heating pad. Always measure temperature in the shade and in several parts of your room. 

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the right humidity for each grow stage

Like with temperature, your plant will thrive on different levels of humidity for each stage of growth.

Seedling sage

Seedlings or clones are at the start of their journey and will not have a developed root system. At this stage you will want a higher humidity so the roots can take in as much moisture as they can. The relative humidity (RH) should be at around 60 to 85%, with the temperature from 25 degrees Celsius (day) to 12 degrees Celsius (night).

Vegetative stage

You can lower the humidity a little at this stage as the plant will start to absorb more water from the soil as well as from the air. Lower the RH to around 55 to 70%, with the temperature being from 22-28 degrees Celsius during the day and 18-24 degrees Celsius overnight.

Flowering stage

During the early flowering stage, drop the humidity to 40 to 50% and temperature at around 20 to 26 degrees Celsius. The temperature can drop even lower when you reach the late flowering stage, at around 30 to 45%, with daytime temperatures being 18 to 24 degrees Celsius and night-time temperatures lowering to 16 to 20 degrees Celsius during the last week. 

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monitoring temperature and humidity

A good way to monitor both the temperature and humidity at the same time is to invest in a good quality thermometer/hygrometer. Some of the cheap ones are known to be slightly inaccurate so get the best one you can afford. Keep monitoring the climate of your room regularly and adjust if it is too hot or cold. It is also a good idea to check your equipment is working well and the room is being ventilated efficiently. 

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About the Author

Our deep love of plants and fascination with Cannabis has enabled over 25 years of successful small scale Marijuana cultivation from indoor hydroponics, greenhouses and outdoor growing set-ups.

As Cannabis laws around the world change, *we support the movement toward freedom of choice for responsible, consenting adults who wish to experience the joy and wonder of growing a Cannabis plant.

*All info is for entertainment purposes only.  We do not condone illegal growing of Cannabis.   Consult your state laws accordingly. 

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