As Winter approaches and brings a drop in temperature it’s vital to think about your growing space temperature to keep your plants happy and healthy.  

This is particularly important when growing in a system, as unlike a soil or coco coir substrate, which offers the root zone a small amount of insulation, growing in water does not. Plants like the air around them to be warm, the right temperature range is about 25-28°C during the lights-on period for your growing space. However, when the lights are off it is best to drop the temperature to about 18-21°C. 

By using temperature, plants can intuitively sense when the cold months are approaching. As the nights get colder and winter starts to set in, plants begin to react to the changing weather conditions. When temperatures start to drop, we see the slowing of plant growth. Temperatures below 18°C will see huge amounts of reduction in plant growth, whereas anything below 15°C could see things come to a complete halt. 

Should your plants' growth be affected in this way, it can take 2-3 weeks for them to return to normal flower/fruit production. Or if you are unlucky, the plant may not recover at all. Nobody wants to lose 2 weeks during a flowering period, especially when it has a direct impact on the size and quality of the plants. To prevent this from happening, here are some ways to ensure your plants are in peak conditions when winter finally comes. 


A well-insulated grown room is critical to maintaining the temperature of the plants. Instead of placing your grow tent on a cold floor, use a carpet or rug as a form of insulation. Wrapping the entire tent with building insulation is also a possibility; if it works to keep your house warm, it will work to keep your plants warm! 


Indoor HID lighting can cause problems during the summer because of the heat they produce. Use this to your advantage during the wintertime by running your ‘lights on’ period overnight when ambient temperatures are cooler, and ‘lights off’ during the daytime. The heat produced will help towards counteracting the cooler nights. 

If plants are still in vegetative growth when winter takes hold, growers should consider increasing the 'lights on' period from 18 - 24 hours. This will just give them a little more heat protection during the cold. 



Just as HID lighting can cause problems throughout the summer. LED lighting can cause problems through the winter. This is due to the LED’s not producing much heat. In order to combat this, I would invest in a grow room heater paired with a thermostat to have complete control over the desired temperature your growing environment needs. One thing to keep an eye on when using a heater is your humidity levels as the heater could dry the air out, resulting in a much lower relative humidity whilst the heater is on. Therefore, I would pair your humidifier with a humidistat so you can set your humidity levels whilst the heater is on. At this point you will have full control over your environment and should any problems arise you’ll have the relative tools to fix them. 

Adding additional light to your set up is one of the most efficient ways you can add extra heat to your growing environment. The extra light will act as a heat generator keeping the temperature raised during harsh conditions and your plants are sure to thank you for the additional lumen output!  

Additional Heating

Heat produced from lights is generally not enough to ensure your growing space is at the optimum temperature, so secondary heating is usually a must!  

Tube Heaters are small enough to be easily placed at any level within your growing space and let out a consistent spread of heat in the surrounding air, keeping your growing space at a steady temperature with a low running cost.  

Tube Heaters are not thermostatically controlled, so if you want that option then Oil Filled Radiators are a compact yet powerful way to establish optimum temperatures and can be used inside a grow tent or room, causing no detrimental effect to the plants. 

The third option is a Fan Heater, although these should be used with caution as the dry, hot air can lower humidity, damage plants and impede growth if blowing directly at them. We recommend they should only be used outside the grow tent or room to warm up the surrounding air or directed towards the intake. If the only option is to have it in the grow space, make sure it isn't pointing directly at the plants, or consider changing it to an Oil Filled Radiator. 

Give your plants some warmth

Your plants may need some help to protect themselves from temperature spikes and really flourish to their maximum potential during the winter months. Vitalink Heat provides a great solution to that problem, a small amount can last a very long time. Using heat before the cold really sets in can help your plants develop a resistance to the cold. Use heat sparingly as overdoing it can negatively affect your plants, sticking to the recommended amounts or even slightly under can really provide some peace of mind for you during these cold months. Directions can be found on the bottle and on our website. 

Nutrient Care

When mixing nutrient solutions, especially in larger volumes and storing it in a water tank over several days, it's vital that the temperature is kept between 18-21°C. If the temperature drops too low, the plants' roots will go into shock, slow down absorption and impede growth. Whereas too warm, the oxygen levels will decrease, plant growth will again slow, but also make them more susceptible to diseases like Pythium, aka Root Rot. 

To combat this and keep pre-mixed nutrient solutions at the perfect temperature, a Water Heater should be used. Being fully submersible, they sit in the water tank and keep the solution at the pre-set temperature at all times. 

Storing the nutrients effectively is imperative as poor storage can lead to damaged nutrients. If storage is too cold, the dissolved salts that make up your nutrients may crystallise and become solid. In this form, they are no longer part of the nutrient solution and remain unavailable to your plants. 

To prevent this, store nutrients in a cool, dark place, out of direct sunlight, where temperatures sit between 10 - 19°C. As a rule, never allow your nutrients to be stored at temperatures below 5°C. 

Watch Your Intake

If you're drawing outside air into your growing space, you're bringing the cold in and making it harder for your plants to stay warm. Move your intake fan so you're drawing air from indoors, making sure it’s from a different area to the growing space. There's also an additional advantage in that air being drawn from inside will not only be warmer, but also richer in CO2. 

You can also use a fan speed controller on both your extraction and intake fans. During vegetative growth and early bloom, turning the fan down by a few percent will allow the warmer air to stay in the room for longer whilst still refreshing often enough for plants to thrive. This, however, might not be an option if in mid to late flower as unwanted growing space odours might require the extraction fan to be on full, therefore secondary heating, as outlined above, should still be considered. 

Monitor Temperature

Plants thrive in temperatures between 25-28°C during lights on, and around 18-21°C whilst lights are off, so it is important to check your temperatures regularly to ensure these conditions are consistently being hit. Using aDigital Thermometeris the best way to identify if something needs addressing to reach the optimum temperature