maintain the ideal grow room temperature
Indoor Growing

How To Maintain The Ideal Grow Room Temperature

Maintaining the right grow room temperature and controlling the heat inside a grow room is a great way to help your plants thrive and grow faster under a grow light.

The climate inside a grow room has a significant impact on the quality of the harvest.

Extremely high or low temperatures can affect the health of the plant and lead to a mediocre yield in terms of quality and quantity. This means that farmers don't make the desired profit.

Beginners and professional gardeners dedicate their time to finding the right temperature for their plants and making sure that they have the perfect environment that encourages growth in their plants.

We've already discussed in one of the previous articles how temperature and relative humidity are inversely proportional and how humidity affects the amount of moisture present in the air.

In this article, we'll be focusing on:

Grow room temperature too high? Read on to know everything about temperature management in your grow room.

What Is The Role Of Temperature In Indoor Gardening?

As you may already know, photosynthesis is the process during which plants use sunlight, water, and carbon dioxide to manufacture glucose. In the place of sunlight, indoor growers tend to use artificial sources of light such as HID lamps, incandescent bulbs, LED grow lights, etc.

The rate of photosynthesis is largely influenced by the grow room temperature. This means that the higher the temperature the greater will be the rate of photosynthesis.

grow temperature affecting plant growth

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As the temperature reaches a particular point, the plant processes such as photosynthesis, transpiration, and respiration increase.

Temperature, when teamed up with appropriate day-length, has an impact on the vegetative as well as the reproductive growth of the plant.

Most biological processes of a plant will speed up as the temperature increases. This means that the plant will grow faster and start fruiting.

Although in some cases, when there is excessive respiration, the plant doesn’t have adequate energy to allow the fruits to grow bigger.

It must also be noted that plant temperature and air temperature are not the same. Plants have the ability to regulate their temperature– they can cool off through the process of evaporation. When the plant heats up due to receiving excess light, the transpiration rate of the plant must increase for it to cool off.

In the next part, let's take a look at the ideal temperature for a grow room.

What Is The Ideal Temperature For A Grow Room?

The ideal grow room temperature depends on the crop variety and stage of growth. For instance, most plants enjoy a grow room temperature of 25°C. Seedlings succumb when temperatures dip as low as 0°C.

grow room temperature for plants

If the temperature in your grow area is not ideal, photosynthesis will be affected. In case the grow room temperature reaches over 40°C, the rate of photosynthesis decreases. This has an effect on the growth and development of the plant.

Of course, there is no ‘ideal’ temperature that applies to all plant categories. Each variety of plants requires a different temperature and approach.

It takes a lot of experimentation to find the right temperature for your plants. Keeping that in mind, one of the most crucial factors that growers should look into is fluctuating temperature.

To ensure that plant processes are carried out efficiently, the daytime grow room temperature should ideally be between 25°C to 35°C. The temperature can be decreased to about 20°C during the dark hours.

With these temperature variations, growers are actually mimicking the seasons that plants experience naturally.

Tropical houseplants enjoy high temperatures, making it necessary to have room temperature and humidity control. Since they are native to tropical rainforests, they can live in temperatures up to 29°C. Growers should ensure that temperatures don’t fall below 16°C.

tropical houseplants

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Generally, tender plants can tolerate a minimum temperature of approximately 15°C while hardy plants can tolerate a minimum temperature of 7°C.

Even though some plants may survive if they are left in colder temperatures for a short duration, they will suffer from damage if they consistently experience extremely cool temperatures.

Growers must try to find the ideal temperature range for their indoor garden. It must be noted that there is no ‘one-size-fits-all’ when it comes to grow room temperature and it may take some experimentation to find the suitable range for your growing area since plants can have varying responses.

While propagating seedlings, growers can stick to a temperature range of 23°C to 27°C. Some growers like to use a germination mat to increase the soil temperature.

When plants are in the vegetative stage, the temperature can stay between 24°C to 28°C and in the flowering stage, growers can dial up the temperature to 25°C to 29°C.

The temperature of the nutrient solution in a hydroponic system also plays a key role.

A nutrient solution is, simply put, a mixture of the essential minerals and nutrients that are required by a plant. This solution is supplied to the plants and it allows them to use the nutrients to grow.

Growers are generally advised to ensure that the nutrient solution is at room temperature, ideally between 21 to 25°C, during application.

The temperature change between day and nighttime periods is something that is often missed by growers. Both daytime and nighttime periods are important.

The shift between day and night time temperatures should be enough to trigger the plant to go through different life cycle stages, but not too drastic to cause damage to the plant.

Carbon Dioxide Supplementation In A Grow Room

Carbon dioxide enrichment can help you increase growth rates by enabling plants to have a better photosynthesis potential.

When growing in a grow room, the carbon dioxide levels are bound to get reduced as plants use carbon dioxide during the process of photosynthesis.

This means that with the help of carbon dioxide supplementation, growers can increase the levels of carbon dioxide in a particular area and increase the yield substantially – some claim that it can increase the yield by up to 30 percent.

co2 enrichment

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The outdoor ambient air that we breathe has a carbon dioxide concentration of 400 ppm (parts per million) while most plants would thrive when the concentration is in the range of 600-1000 ppm.

When supplementing with carbon dioxide in a grow room, the temperature should ideally be in the range of 30-35°C. Growers are recommended to have a sealed grow room to avoid any carbon dioxide from escaping.

Most plant processes increase with a rise in temperature – including photosynthesis. In a greenhouse that is enriched with carbon dioxide, increasing the temperature can lead to faster growth in plants.

Carbon dioxide enrichment increases the co2 grow room temperature needs of the plant. In simple words, plants would require a warmer grow room to use the carbon dioxide.

Gardeners who already deal with high temperatures in their grow room may find it beneficial to have CO2 enrichment.

Studies have shown that CO2 enrichment also allows you to increase the number of fruits per plant in tomatoes, lettuce, and cucumbers. Pairing grow room temperature with co2 can help you to have a higher yield.

In the next part, let's find out exactly how you can maintain grow room temperature.

How To Maintain Grow Room Temperature

Grow room temperature is influenced by several factors such as the size of the growing area, air circulation, variety of plants that you’re growing, the location of your grow room, the lighting system and so much more.

For instance, basements are typically colder than a bedroom and may require extra heating equipment to ensure that the area is warm enough.

Ideally, your grow room should have a stable or uniform temperature. This means that all the plants should grow at a uniform rate.

This can be hard to achieve, especially for growers who have grow lights with a high heat output (such as fluorescent light bulbs). The higher the heat, the more methods of heat extraction would be required in the setup.

Before getting started, it is crucial to have a grow room temperature monitor or a thermometer to measure the temperature of your grow room.

To achieve the best results, the thermometer should be placed away from the lighting system. This allows it to capture accurate readings. Additionally, growers may need to cover the thermometer and give it shade so that it provides accurate information.

They must also focus on root temperatures since it greatly affects the nutrient uptake and the growth of the plant. Along with a thermometer, having a hygrometer to measure the humidity in the air can be tremendously helpful.

Growers are advised to get readings from different spots inside the grow room to make sure that the temperature is uniform across the canopy. Since temperature varies throughout the house, the easiest way to deal with excessive heat in a grow room is to try changing its location.

Since we're talking about equipment, we recommend having an efficient air circulation system as a part of your grow room temperature control strategy. It makes a huge difference and ensures that there is fresh air in the grow room and stale air is drawn out.

air circulation in grow room

Image Source: Leafly

An active intake system involves drawing fresh air inside the grow room through an intake port. It is an efficient way to manage heat inside a grow room.

Such a system is recommended for growers who have a large growing area (or a commercial setup) and also have the resources to invest in the system.

What Are Hot Spots In A Grow Tent?

'Hot spots' are basically areas that fall directly under high-intensity lighting sources such as HID lamp lights. Plants that fall underneath these lights are prone to damage.

Hot spots can cause uneven growth in your grow room with some plants growing faster than the rest—this means that growers may need to move plants away from the source of light. Plants that grow in these hot spots need to be supplied with more nutrients since they receive more light than they require.

Oscillating fans or clip-on fans in an air circulation system help eliminate these hot spots by moving air throughout the plant canopy. These fans are low priced and ideal for growers who are on a budget.

What Are Heat Sinks And How Do They Work?

LED grow lights are becoming increasingly popular in the horticulture industry by allowing growers to cultivate crops affordably and grow fruits and vegetables indoors.

These grow lights allow gardeners to grow produce even in areas that lack natural light. Even though most LED light fixtures produce minimal heat, the operating temperatures can affect the durability of these fixtures.

Some beginners are unaware that the grow lights that they use can be making the climate uncomfortable for your plants because of the heat that they give off.

To battle this heat, many lighting systems come with a device known as a ‘heat sink’. As the name suggests, a heat sink is a medium that absorbs the heat that these lights give off and redirects it back to the surroundings.

Heat sinks can be made up of different materials (aluminum alloys, for example) and come in a variety of shapes. The kind of heat sink you require depends on the structure of the lights that you have.

To ensure that you get the most out of your lights and junction temperatures do not cause your lights to lose their effectiveness, it is important to have heat sinks as a part of your lighting system.

In case you’re using lighting systems that have a high heat output, such as HIDs, you may need to experiment with the placement of the lights and bring them closer or raise them higher to adjust the led grow room temperature.

Different from grow lights like HID, LED grow lights have a comparatively lower heat output and you may require installing a heating system or a mini-air conditioner to keep the temperatures controlled.


Grow room temperature and humidity control are crucial for achieving an exceptional harvest. Whether you're growing in a greenhouse or grow room, the aforementioned pointers can help you get desirable results.

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