How to Add Humidity to A Grow Room

In my many years as a gardening professional,I have come across many families and friends who have shared with me the many challenges they faced in their novice attempts at gardening, not surprisingly,it all gravitated towards the same problem.

One September I remember a client I had worked with for a while called me to explain a reccuring problem she was having in her grow room.She was cultivating vegetables and the leaves were starting to curl, a neighbor had suggested spraying water to the leaves and adding more water to the soil content but that just slowed down the problem, I had to pay a visit to her garden to properly asses the situation first hand.

On arrival, the problem couldn’t have been more obvious to me, it was so hot that the humidity in her grow room was very low. Explaining the problem to her along with the different ways she could save her garden, humidity is a vital factor on the growth of any plant moresore if the plant will be grown in a grow room, everything from the type of light we use to provide light to the plants to the pace of a ventilator fan should be taken into consideration.


Different plants require different humidity level for optimum growth, but we have to understand humidity and its effects on plants in a grow room.

According to Wikipedia, humidity is the concentration of water vapour present in the air. The reason why it’s important is because plants need water for survival and as they draw water from soil, 95%of it is released in the stomata during transpiration. This process must occur in perfect harmony. If the plants looses more water than it absorbs it start wilting.

It’s not only the internal physiology that gets disrupted, external environmental factors, negatively or positively affects the plants depending on the humidity. Optimally, at a favorable humidity, leafy plants grow to their full potential but when conditions are too humid, different kinds of molds and insects attack the plants, at low humidity,the plants wilts.

There are ways of maintaining optimum humidity to ensure good plant growth. Firstly, you need to measure the humidity before you can control it, you thus need a hydrometer. This is a device that measures the humidity in a room and can give precise reading as per the prevailing conditions, they are sold on amazon and I have found them to be invaluable in maintaining optimum humidity.

Now that you know the prevailing humidity here are ways to optimize humidity levels in your grow room:


These are a great option to increase humidity in your grow room or grow tent,you can pick various models online with variable capacities, personally, I have found the Varnado evap 40 to be a reliable model.



Because grow rooms get limited light from the sun, artificial light required to provide the lux needed for optimal plant growth, but if you are having a problem with the humidity in your grow room it’s time to look at the light. If you have traditional light like fluorescent and incadescent bulbs, simply switching to LED lights will reduce the amount of heat in the room while still maintaining the same level of LUX. LED lights consume less power and are known to be as much as five times brighter than other conventional forms of lighting, in my experience ,phillip dimmable LED lights are quite reliable, watch out for bulk sales on amazon.

Mixing old plants with young plants, although it’s a bit controversial it actually works, I was understandably a bit skeptic when trying this method but it worked and the science behind it is simple, older plants have well developed roots hence they would take in more water and perspire more than young plants thus increasing the relative humidity in the room.


Having a fan in the room will help maintaining humidity. When the fan is set at a low pace it cools the air in the room, this has the effect of reducing the rate of water loss by plants during low humidity and prevent wilting. It’s important to purchase a fan, you can choose a variety on amazon, and if you have one, remember to set it at a low pace in low humidity and at a higher pace in high humidity to encourage air circulation.

Wet towels

The theory here is that, placing wet towel at different places in the grow room would increase humidity as water evaporates from the wet towels water content increases in the air, you have to pick absorbant towels for this test, the bigger the better it can hold more water content.

Humidity absorbant plants

Nephrolepis exaltata, the sword fern, in plant nursery

High humidity is equally detrimental to plants, for people with this problem consider adding humidity absobant plant to the grow room, plants like peace Lily, reed palm and boston fern among other can help regulate humidity in areas plaqued by high humidity.

Place water in the grow room

Placing water in bowels or open container at various points in the grow room increases humidity because water would evaporate from the water to the air, a better or rather quick way of humidifying a room is to keep the water near a heart source.

Air conditioner/fan heater

Air conditioner inside the beautiful room

In either high or low humidity AC and fan heaters are useful in controlling humidity. A fan heater can be used a heater when it’s cold and as fan when it’s hot. Most fan heaters are small and can be hanged on a wall, they occupy minimal space and are piling and play, the optimus H-1322 fan heater has proven to be more than reliable and can be found on Amazon, for a good portable AC I have come to rely on the LG LP0817WSR portable stand alone AC which can also be found on amazon.

In conclusion, humidity is essential regardless of any plant you grow, it is imperative that you research and find the optimal humidity for your plans and apply the various methods expounded in this article.

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