The temperature while growing marijuana is not just about calibrating a few degrees here and there. Ensuring that the plants have the perfect temperature is both an art and science.

Providing the right temperature can get quite complicated when you are growing them indoors. You need to recognize temperature related issues and make certain adjustments.

I will explain in the following article all that you need to understand to figure out the ideal temperature when you grow your marijuana. But why is temperature such a crucial factor for producing the best weed possible? Let’s find out.

Effects Of Temperature On Marijuana Growing Process

Cannabis plants are not self-sufficient when it comes to temperature. Unable to create their heat like humans and animals, they depend entirely on their environment. Though a thermometer can’t measure it, the temperature can ascertain a plant’s health through its temperature.

I have found, extreme heat can slow down cannabis plant growth. If the external temperature is high (above 80 degrees) while flowering, the buds tend to grow slower, and their aroma and potency reduce.

High heat impacts protein production and decreases enzyme activity. Some proteins might even break down. The plant can eventually die if this continues for long enough.

1.    Impact on Photosynthesis

Photosynthesis can safely occur at 60ºF (15ºC) or 85ºF (30ºC), and your plant can produce adequate sugar. However, it needs more than 68ºF (20ºC) to distribute the sugar.

High heat stunts the growth of immature plants. The mature ones can handle occasional heat. They back up the sugar, and once the ideal temperature is restored, sugars reach wherever they are needed.

2.    Temperature Sensitivity And Respiration

Lowered temperature decreases respiration. Though this lowers the amount of energy used by the plant, it eventually becomes a problem.

If crop development is heavier due to reduced temperature, crop respiration spikes up. Thus, with more energy required for the plant’s sustenance, very little is left for plant growth.

3.    Other Problems

High temperature increases the chances of root rot, nutrient burn, increased stretching and wilting. The plant might also suffer from white powdery mildew and spider mites. High humidity or increased water transpiration can make the situation worse.

4.    Impact On Growth Stages

The cannabis plants respond to temperature differently in different stages of their growth. From clones and seedlings to the harvest, I always provide my plant babies with the right temperature in each stage.

5.    Seedlings And Clones

High humidity is essential for the clones as they depend solely on transpiration for water in the absence of a root system. 68-77°F (20-25°C) is needed for the clones and seedlings for forming roots quickly and becoming more self-sufficient. I often use a humidity dome to create an ideal humidity for clones.

6.    Vegetative Stage

Your young plants would love temperatures between 68-77°F (20-25°C). During this stage, they will also need high humidity (70% or more). Temperature can be slightly lowered as they grow older.

Though young cannabis plants enjoy slightly cooler temperatures during dark periods, ensure that the temperature does not drop below 59ºF (15ºC).

Cooler dark periods perfectly encourage growth. A mature plant withstands drier air and cooler temperatures during the day.

Outdoor grown plants can withstand temperature fluctuations better than indoor grown plants.

  1. Flowering Stage

A comfortable room temperature with low humidity can make the cannabis plant thrive during its flowering stage.

Keep your growing room temperature under 82°F (28°C) unless you are providing additional CO2. This will ensure aromatic and potent trichome rich buds.

Higher temperatures not only slow down bud growth but also cause terpenes to evaporate. Terpenes are aromatic compounds that create the characteristic cannabis taste and scent.

Terpene production is at its peak during the 6th or 7th week. Take extra care to maintain a comfortable temperature at this time as the risk of losing them is greater too.

You can also lower the temperature slightly during dark periods. This will optimize the plant process and might boost terpene production.

Terpene also lends color to the plant. Depending on the strain, proper dark period temperatures can trigger interesting colors such as red, blue, purple and pink.

Seeds with stable genetics ensure a great concentration of Terpene. I swear by the seeds from Homegrown Cannabis Co for a high-quality yield.

  1. Drying and curing

The quality of marijuana is also largely influenced by how it’s dried or cured. Maintain around 64°F (18°C) temperature and 45% humidity after harvest. This will help prevent mold and overdrying.

Symptoms of incorrect temperature

The leaves tend to get curled from the edges if it’s too hot. Too much proximity from the bulb can cause leaves to curl upwards. The plants will be smaller if it is too cold.

9.    Ensuring Optimal Temperature 

Let me now share how you can create a temperature that would make your cannabis plant babies thrive.

  1. Outdoor growing

Though most outdoor varieties can endure temperatures as low as 50°F (10°C) with ease, it tends to impede growth and photosynthesis. Tissues get damaged if the temperature falls below 40°F (4°C).

I resort to polyethylene plastic covering or gas patio heater to keep the grounds warm on chilly nights to maintain a temperature of at least 60°F.

  1. Indoor growing

Generally, cannabis grown indoors functions best between 68 and 77°F (20-25°C) during the light period. The dark period temperature should be around 18°F (10°C) to 60°F (15°C). Supplying additional CO2 will make the plants give out slightly higher temperatures around 82°F (28°C).

To maintain the ideal temperature in your grow room, you need to take note of certain factors—for example, the room’s location. An attic will be warmer than a grow room in the basement. The number of lights and the size of the room is also very important, along with the airflow and the extraction rates.

A minimum-maximum thermometer and hygrometer must be installed in all grow rooms, asserts horticulturist Jorge Cervantes and so do I.

For cuttings and seedlings, keep the temperature between 68ºF and 77ºF (20ºC and 25ºC). The rate of evaporation increases as the plants grow older. You can increase it to a maximum of 82ºF (28ºC).

For the ‘dark’ periods, ensure that the temperature is between 59ºF and 72ºF (15ºC and 22ºC). Be careful to keep the temperature difference between day and night less than 18 degrees.

A heating mat can be ideal if you have fewer plants. A steady floor temperature of around 80°F (27°C) will warm the roots. It will also help the leaves and stems withstand cooler air. For larger gardens, use a recirculating hot water heater.

Ensure enough distance between the lamps and the plant. Radiant heat from lamps does not affect the air temperature, but it will be warmer by a few degrees than a shaded spot.

Identifying Temperature

You can use either an analog or a digital thermometer in your marijuana grow room. I always prefer a digital Thermo/hygrometer with built-in memory. They enable me to keep track of the maximum and minimum temperatures.

Tips For Identifying Temperature

  • The temperature must always be measured in the shade.
  • Take temperature at various places in your grow room.
  • Place several fans to provide good airflow.

Correcting Temperature Errors  

Keep your lamps a bit higher than the plants to prevent heat stress. You can also use a fan to minimize excess heat. Air-cooled lights with reflectors also solve this problem. I like to keep swivel fans aiming between the plant and the lamps to ensure even distribution of heat.

From a Co2 generator to a space heater or radiator with a thermostat, there are plenty of ways to amp up the temperature when the lights are off. For regulating higher temperatures, use a heat extractor. If you keep your lights on from a few hours after the sunset till a couple of hours after the sun rises, you can ensure a low temperature.

Provide optimum temperature for your plants to ensure a successful harvest. I hope this article brought you clarity about the best practices regarding identifying and adjusting the temperature.

Here’s wishing you a heavenly harvest. Happy growing!

admin