The importance of controlling a grow room’s climate can’t be stressed enough. This is true for every indoor garden, from the garage-scale operation to the largest of warehouses.
Since nobody in their right mind goes into production seeking to grow low-quality flowers, we’ll assume you’ve invested in proper lights, ventilation, dehumidifiers and AC units. However, what gets lost in the mix sometimes is a controlled way to introduce humidity into a space.
Telltale signs of leaves curled upward or brown-tipped leaves might mean your garden is lacking the Relative Humidity (RH) it needs to thrive. This is most common with young seedlings, but can also occur in more mature plants in extreme cases. To understand how to deal with this, it’s best to also understand what we’re dealing with and why.
The Root of the Problem
In most cases, RH problems arise in young plants and seedlings with underdeveloped roots. This is because the plant can’t yet take up enough water to support itself, so most of its water intake comes through the leaves. If humidity levels are too low you’ll end up with leaves curling upward like little spoons. Or, if roots are a bit more developed, low RH will make the young plant drink excessively which will often lead to “nutrient burn,” characterized by brown tips on your leaves.
A higher RH in the early going keeps a plant healthy while the roots are developing and promotes vigorous growth which will translate to higher yields later. This is why some growers choose to start their seedlings in propagators.
Relative Humidity Explained
As simply as possible, relative humidity (RH) is the amount of water vapor possible in the air at a certain temperature – expressed as a percentage. The higher the temperature, the more vapor it can hold. So it stands to reason, the lower the temperature the less it can hold. Understanding this is important to knowing how you can address RH in your growing space.
RH has a sort-of yin yang relationship with temperature in that raising or reducing it has the opposite effect on RH. Raise the temps with the same amount of water vapor in the air and RH goes down, lower the temps, RH goes up.
Knowing this, that means we have two different ways to increase RH, either:
A) Increase the amount of water vapor in the air without affecting temperature, or
B) Lower temperature with no change to existing water vapor
Dealing with Low RH
OK, as promised, here’s a quick-and-dirty rundown of five easy ways to deal with low RH in your room.
Lower the Temperature
It’s almost unfair to include this one since it’s fundamental to how RH works. So, as a bonus, make sure your grow room is sealed and insulated from the outside to avoid even incremental external influence on temperature since temps and RH go hand-in-hand.
Hang Wet Towels or Sheets
If you’re happy with the temperatures in the room, then adding water vapor may be a better option. Hanging towels is not a long-term solution and rings of a basement/garage method, but your plants don’t care where the RH came from. This can help out in a pinch.
Water Bowls Near Air Intakes
Placing a bowl of water with air flowing over the surface will promote evaporation, increasing the amount of water vapor in the air without affecting overall temperature. To further increase the effectiveness of this, add a sponge to the bowl or trays to increase surface space which will add vapor to the air even quicker.
Add Larger Plants to the Room
Larger plants perspire more than seedlings which will increase the overall RH in the room. This option may not be for everyone, especially where garden space is at a premium.
Introduce a Humidifier!
The ideal option is to introduce a humidifier with automated climate controls. With any of the previous options, the addition of humidity or lowering of temperature adds an approximation of RH value rather than a concise amount. For complete control, add a humidifier.
OK, so really this was just a long way of saying, “Use the right tool for the job.” But if you’re running into problems with low RH, hopefully this helped you understand the causes of the problem and gave you some stop-gap options until you can make the investment in humidifiers. Happy growing and as always, #ControlYourGrow