Cold temperatures kill plants, not just marijuana plants; and so do very hot temperatures. Indoor plants especially need extra care as mother nature is not there to help them. You as a smart grower should take extra precautions as the coldness will find its way into the grow room during winters.
None of us growers wants the fall in temperature to affect the leaves and the growing ability of the plant, eventually leading to lesser yield and poor quality buds. Grow room heating is paramount to achieving the desired results.
We at 6to5 Grow have been very concerned about the grow room being too cold for quite some time now, and since growing marijuana has been my passion for such a long time, it was important for us to find the right ways to fix the grow room’s temperature.
The issue was more so important to solve as grow room gets too cold at night during the winters. The good news is that there are simple yet clever hacks to fix a cold grow room, and I am here to share them with you.
How Cold is Too Cold for a Grow Room?
Is my grow room too cold? Asked my growing friend. The temperature inside the grow room is never the same throughout the year no matter which LED Grow lights you use. You most definitely do not keep the LED grow lights on all year long. Temperatures in the grow room should always be kept at an optimum for the best yield.
Temperatures that are below 60°F (15° Celcius) will shock or kill the plants, which is usually the case during winters in the US, UK and the EU and also slow down the growth leading to a poor yield if at all they survive.
On the other hand, when temperatures rise above 80°F (26°Celcius), it will slow down the growth of the bud due to loose and airy conditions.
Ideal Temperature in the Grow Room
Unless you have been growing for a very long time, there is a 94% chance you might be unaware of the ideal grow room temperature for your plants.
While different seed bank seeds require varying temperatures for them to thrive and deliver the best yield, there is an ideal temperature range within which the grow room should fall at any given point in time. Ensuring your grow room falls within this range will ensure maximum yield for your buds.
Ideal temperatures also change depending on what phase your plant is at. Let us understand these phases and the range.
Vegetative Phase: 70-85°F (20-30°Celsius)
While most of the growers (including me, during my rookie stage) focus on the flowering stage right away, the baby phase stands as a foundation for high-quality high-yield buds. This is a stage where the plant matures and the leaves blossom out.
At this stage, the plant requires a relatively higher level of warmth and therefore the most ideal temperature range is between 20 to 30°C.
Flowering Phase – 64-80°F (17-26°Celsius)
This is the stage where the buds blossom out and the temperature of the grow room will decide the yield and quality of your buds. The most ideal temperature range is between 17-26°Celsius.
When the plant arrives at this phase, you can lower the temperature a bit in the grow tent as it will give the buds a better color, smell, and density.
Having a temperature difference of 10 degrees between day and night will ensure the highest growth yield of your plant. Some grow rooms even have a temperature as low as 10 degrees celsius, but let’s keep them within the range mentioned above.
Monitoring the Temperature
Unless you are a retired person/couple, there is a higher probability of you not being around the grow room all the time to maintain the ideal growing temperatures. Come on, we all love big vacations, especially during summers, don’t we?
We need something that can help us monitor the temperature inside the grow room remotely, as opening the grow room or grow tent often can disturb the temperature inside too.
Using Min-Max Temp Thermometer is a good idea to do just that. The thermometer I recommend and use is ThermoPro Indoor Outdoor Wireless Thermometer with Humidity. Another one is a convenient remote controlled Thermometer called AcuRite Wireless Thermometer that does a similar job to ThermoPro, but having options is what we want these days, right?
Grow Room Too Cold Symptoms
While the thermometers mentioned above will do a good job keeping you informed of the temperatures inside the grow room, having an understanding of the symptoms of change in temperatures damaging your plants to an irreversible stage is a good idea.
Some of the several signs of your grow room being too cold are:
- Loss of color, density and smell.
- Damp areas and moulds (during summers).
- Change in yield density.
- Weaker growth quality.
- Eventually rotting of the root.
Now that you have an idea of how cold your grow room is getting, and whether it is affecting your germination and plant growth, let us see what are some of the hacks and fixes to bring the grow room temperature to the ideal range using easy grow room heating technics.
7 Actionable Solutions to Reduce Grow Room Temperature
Enough with the problems and nightmare talks. Let’s talk about the brighter part from hereon by raising the temperature of the grow room with these simple yet effective hacks and solutions to the ideal levels.
Before you spend hefty bucks on any temperature raising equipment like big heaters, follow these remedies that cost a single restaurant outing’s worth.
Use Soil Mats
When we talk about cold temperatures, most growers think of the cold air in the grow room. A handful of smart ones think of the soil beneath the plant. When someone faces hair fall, we usually work on the hair strands and not the scalp which is where the most problem lies.
The warmth of the soil is extremely important. When the grow room becomes cold, the soil becomes cold as well, directly affecting the roots of the plant. Cold soil makes it difficult for the plant to absorb the nutrients and water in the soil.
It is evidently important to use soil mats, especially during the germination stage. More so, not just during germination, soil mats and warm soil is critical in the entire yielding phase to keep the temperature to the ideal levels.
I highly recommend using VIVOSUN 10″ x 20.75″ Seedling Heat Mat for every 3 or 5 plants that give the exact temperatures mentioned above (20-30 degrees celsius). There is no setup required, a plug-and-play mat that comes with a controller. It costs a mere $30 with free shipping, order according to the number of plants in your grow room.
This is also our most recommended solution for grow rooms too cold!
Insulate, Insulate, Insulate!
You’re already dealing with a cold grow room, especially during the nights. When you get that little warmth during the winters, you do not want the heat to go out of the grow tent or the room. Insulating the plants will make sure the warmth is trapped inside for the plants to use.
You do not need expensive insulating materials or insulating the air ducts. There are many ways in which you can insulate a cold grow room. Here is how insulation can work with little work.
- Firstly, if you are growing buds in a pot, cover the pot with Aluminium foil sheets.
- If the plant pots are directly in contact with the cold floor, use Polystrene Plastic Sheets if you do not wish to buy soil heat mats.
- Lastly, if the temperatures where you live go totally nuts, wrap the whole grow tent with insulation in such a way that no heat goes out of the tent, nor does the cold come in during the chilly winters.
Use Grow LED Lights Effectively
Grow LED lights are an effective source of providing warmth to your plants especially during their germination stage.
A normal grower keeps the light off during the day as the heat from outside does the job, and turns it on during the night – in the summers. But this changes completely during the winters. A lot of growers would use heaters for a few hours during the night and LED lights during the day.
I recommend keeping as many grow LED lights as possible turned on 24 hours during the cold temperatures. Now, you might be shocked at this statement thinking of the electricity bill. Trust me, keeping the lights on 24 hours is much cheaper than using the heaters for a few hours a day. Moreso, some power companies give cheaper electricity rates during the night and that will save you some money.
However, turn off the LED lights for certain hours (4-6 hours) during the day every other day as the plants need some hours of darkness to rest and grow effectively. This works the best during the vegetative phase and maturing phase. During the flowering stage (final stage), keep the lights to a minimum and let the insulation do the job.
Improve Air Circulation
No amount of LED lights or heaters will work if the heat does not actually reach the plants. This is where optimum air circulation comes into play. A simple table fan or a standby fan will make sure the heat circulates around the grow tent or cold grow room and does not create heat hotspots.
If too much heat is concentrated in a single spot or on a single plant, the plant is ought to die as well. A grow room fan is an ideal solution.
Use a Thermostat Radiator
Unlike the tube heaters, oil-filled thermostat radiators are thermostatically controlled. They are very compact and do not take much space even if you have a small grow room indoors. I use Pelonis Electric Oil Filled Radiator for my room as it can be easily controlled using the digital display so that I achieve optimum temperatures recommended above.
Warm Nutrients with Aquarium Heater
As we have said before when the temperature in the grow room goes down, the soil and eventually the roots get affected too. Therefore, the roots do not take in water and nutrition as desired.
A lot of growers also forget that the nutrient solution you will be putting in the soil gets cold as well. You need to heat the nutrient solution before adding it to your plants. Mix the nutrient solution in a container and heat it up using the aquarium heater. However, make sure the solution is not overly hot (normal temperature suffices) as it will burn the roots of the plant.
Alternatively, you may also increase the strength of your nutrient solution to nullify the loss of absorption due to cold grow room (if you do not have an aquarium heater).
Grow Room Humidifier
Cold temperatures often come with dry, chilly air. It takes away the moisture and humidity from the room or tent. This makes the plant leaves dry, lurking for moisture to keep them moist and warm.
A grow room humidifier will ensure the tent is kept humidified during the night of chilly winters. Since I live in the coastal state of the USA, humidity is something I am not quite worried about, however, my friends in other states require a grow room humidifier to keep their plants moist.
After talking to a handful of grower friends, the best humidifier for a grow room came out to be from Ideal-Air Commercial Grade Humidifier. This grow room humidifier is big and powerful enough to cover the entire growing space that you might have.
Frequently Asked Questions
No, and yes. It basically depends on how much damage has been done already. If the damage is caused only on the leaves, the damaged leaves will fall off and new leaves will start blossoming with effective heating techniques mentioned above. If the roots and stem have been damaged, it’s time to bid adieu to the plant.
Spending a lot on the entire cooling unit can sound scary when you have already invested so much. The cheapest option for the grow room going too cold is to use soil mats, insulative the pots and the floor, and an aquarium heater. Using a sub-$100 oil-filled heater is quite handy too.
The first thing to do is check whether the roots have been damaged. You can also check the discoloration and other issues mentioned above, if so, the problem is now irreversible. It is time to change the plant and execute the above hacks.
It definitely depends on the temperature outside, and how much temperature the plant in the particular growing phase demands. The usual time is after the evening, but during winters, the heating should continue throughout the day and night.
My friend Everest made a video explaining all of the methods above for you to understand how to keep a grow room within the appropriate temperatures.
Over to you, buddy
Seeing the plants die because of a cold grow room is a painful thing to watch. Growing marijuana is a temperature-sensitive activity that you need to take care of all the time. Hence, using the thermometer recommended above will help you with the task of monitoring actively.
The idea is quite simple. Keep the temperature and humidity of the grow room within the recommended levels using the solutions mentioned above, especially during winters when the grow room gets too cold.
Warmth is the most important thing for the plants to grow with better yields, just like a newborn who needs the warmth of a mother to keep the body functioning.
Grow room too cold? No more.