Calatheas have a well-earned reputation as difficult houseplants. One of the most persistent obstacles in raising these moody beauty queens is providing enough humidity to satisfy their powerful craving for moisture. This article will explore why it’s so hard to get the proper humidity levels for Calatheas and explain what you can do to overcome this challenge.
Calatheas are happiest when the ambient humidity is around 80%, but anything above 60% should be enough to keep them in good health. Below that, your plant’s growth may be impaired, and its foliage may become curled, crispy, and brown. There are a few tricks that will enhance the humidity around your Calathea, but investing in a compact humidifier is the surest bet.
Finding the right location also helps – try placing your plant in a well-lit spot in your bathroom or kitchen, and always keep it away from vents that blow hot air. Too much direct sunlight also exacerbates existing humidity issues. We’ll cover all of this in more detail below, and suggest a few more tactics to keep your Calathea nice and humid.
Why Do Calatheas Need So Much Humidity?
Plants keep themselves healthy by maintaining a delicate balance with the world around them. In order to draw life-sustaining water from their roots, they shed vapor from pores in their leaves called stomata. The tiny amount of suction generated by the escaping water molecules helps to pull more water up. It’s as though the stems of the plant are straws from which the air itself is drinking.
The release of moisture from leaves is known as transpiration, and under normal circumstances, it’s vital for a plant’s health. But when something upsets the balance and causes the foliage to lose water faster than the roots can replace it, the leaf cells become dehydrated, wither, and die. Low humidity is a prime example as dry air draws water vapor from the leaves much more rapidly.
Some plants have thick foliage that stores a fair amount of water to protect against this effect – the plump leaves of succulents are a good example. Calatheas lack this defense. They evolved in moist, misty jungles where lack of moisture is almost never a concern, so their foliage is quite thin. Anything that pushes the rate of transpiration too high will dry out the leaves with remarkable speed.
Special Humidity Concerns
Certain circumstances leave your Calathea particularly vulnerable to low humidity. The first and most obvious is the winter – for those of us living well north of the equator, this is the driest time of the year. Give your Calathea some extra support when it gets frosty outside.
Also, any time that the root system is stressed or damaged, your plant will be more susceptible to humidity problems. Any time you move your Calathea from one pot to another, you should take extra care to keep the air moist while the plant recovers from the shock. The same advice applies after you’ve propagated a Calathea by root division, or pruned its root system to get rid of an infection.
Signs That Your Calathea Needs More Humidity
When the ambient humidity is too low for your Calathea, the leaf cells begin to die off, creating papery brown patches on the foliage. Usually, the edges of the leaves dry out first, since they’re the thinnest spots. You’ll often see a leaf that looks mostly healthy except for a narrow brown crust around the edges.
The leaves might also curl in at the edges, resembling a scroll being rolled up. This is the plant’s attempt to reduce the amount of surface area exposed to the air so that not as much water can escape. The leaves might also go limp – they rely on the internal pressure of moisture in their cells to stay rigid. Finally, sluggish or stalled growth could be a sign that your plant isn’t getting enough humidity to live its best life.
However, there are many other issues that can dehydrate a Calathea’s leaves, causing similar or identical symptoms. Confirming your plant is low on humidity requires ruling out all the other things that could be wrong with it.
- Underwatering. If you don’t give your Calathea enough water… its leaves will run out of water. Shocking, we know.
- Overwatering. This one is a little less obvious. Too much water chokes off the oxygen supply to your plant’s roots, preventing them from absorbing the moisture that keeps the leaves content.
- Mineral buildup. Tap water or fertilizer can leave behind salts in the soil, which also interferes with root function.
- Sunburn. Calatheas are sensitive to direct sunlight, which dries up their foliage in much the same way as low humidity.
- Heat. Just as you sweat more when it’s hot, Calatheas lose more water from their stomata in temperatures above 85 degrees or so.
Diagnosing Low Humidity in Calatheas
Start by measuring the ambient humidity directly. A cheap hygrometer from a garden store or online retailer can give you a pretty precise idea of how much moisture is in the air. Remember, you want that number to be above 60%.
Even if the humidity seems low, it’s a good idea to eliminate other suspects. Humidity is just one piece of the puzzle; a Calathea with disrupted roots or stressed-out leaves will be much more susceptible to dry air than a healthy one.
First, make sure that your Calathea is getting the right amount of hydration. The best way to time your watering schedule is to check your plant’s pot every few days by sliding a wooden skewer down into the base of the soil; you should water only when the tip comes up very slightly damp.
For a less precise but faster method, you can test the top two inches of soil with your finger. When that upper portion has dried out, it’s time to water again. The finger test isn’t as good as a wooden probe for deeper pots, but it will do just fine for small to medium-sized Calatheas.
Once you’re sure you’re not overwatering your Calathea, try giving it a soil flush to eliminate any built-up salts. Slowly soak the soil with a whole bunch of filtered or distilled water (at least 3 times the total volume of the plant’s container), allowing it to permeate the mix and drain out the bottom. Hold off on fertilizing your Calathea for a week or two afterward, and water it only with distilled water if you can.
Did that get rid of the problem? Congratulations! You had an issue with soil minerals, not humidity.
You can rule out sunburn and overheating if you’re confident your Calathea hasn’t been exposed to more than 2-3 hours of direct sunlight each day, or to temperatures outside its healthy range.
Now that you’ve eliminated the other suspects, it’s pretty safe to guess that the humidity is what’s causing your Calathea to suffer.
How to Increase Humidity For Your Calathea
Indoor gardeners are no strangers to the difficulty of keeping tropical plants humid. Over the years, the houseplant community has developed a wide range of tools and tricks to step up the moisture around plants like Calatheas.
Some of these methods are much more effective than others. We’ll review the most popular strategies, beginning with the most useful:
Humidity Tip #1: Use a Humidifier
A simple electric humidifier is hands-down the most effective way to combat dry air around your houseplants. By gently dispersing a stream of ultra-fine mist, one of these machines will keep moisture levels elevated for hours at a time. And the only effort it requires from you is filling a tank and pushing a button or two.
Our favorite is this Warm and Cool Mist Humidifier. As the name implies, it allows you to modify the temperature of the vapor it releases – useful since Calatheas are sensitive to heat and cold as well as dry air. Winter is often the time when you need extra humidity the most, so it’s great to be able to warm up your tropical beauties while you moisturize them.
On top of that, this model has a large tank that you won’t need to refill every day, and the ultrasonic vibrations it uses are so quiet that you’ll hardly notice the machine is there. You can set it to the precise humidity level you want – we’d advise choosing a level around 60%, which is enough to satisfy your Calathea without making you feel like you’re constantly sweating.
This 6L Humidifier is at the higher end of the price range for portable humidifiers, but in our opinion, the added ease and control are worth it. We highlight some less expensive options in this article on houseplants and humidifiers.
Whatever model of humidifier you opt for, make sure you clean it once every week or two with a dilute solution of white vinegar. Otherwise, it might breed mold and bacteria.
Humidity Tip #2: Location, Location, Location
Not all rooms are created equal when it comes to humidity levels. You can reduce the effort it takes to keep your Calathea moist by choosing the right spot to house it.
Bathrooms are a popular choice. Plated with moisture-retaining tile and regularly doused with steam, they’re usually among the most humid rooms in the house. They don’t always have enough illumination to keep a Calathea happy, though – these plants need lots of bright, indirect light to thrive. But if your bathroom has, let’s say, a big south-facing window with frosted glass panes, it might be the perfect spot for your Peacock Plant.
Kitchens are typically better-lit than bathrooms and are often nearly as humid. Your Calathea might be happier if you let it keep you company while you cook.
You should also take into account the size of the room if you’re using a humidifier. High ceilings and wide, open-plan living areas feel very luxurious, but they’re also much harder to fill with water vapor. A smaller space will make it easier to provide adequate moisture for a Calathea.
Pay attention to your heating and cooling setup, too. Placing a Calathea near a heater or an AC unit may deny it the humidity it needs since the air that comes out of these systems is quite dry.
Humidity Tip #3: Give Your Calathea Some Neighbors
There’s a reason that Calatheas thrive in rainforests filled with other vegetation. As each plant pulls moisture up from the soil and releases it from its foliage, it’s adding a little bit to the ambient humidity. That benefits any other plants nearby.
So if you have several tropical plants, you can make all of them happier by grouping them near each other. Before long, you may find yourself with one of those gorgeous greenery-filled sunrooms that look so great on Instagram.
Calatheas do need a bit of air circulation to stay healthy, though. Don’t put them so close to other plants that their leaves are touching. A little space will help them breathe.
Also, inspect every plant carefully for signs of a pest problem before adding it to your indoor jungle. Harmful critters like spider mites can spread through your collection quickly. If you do notice any pests on a plant, quarantine it from the others until you’re certain you’ve eliminated the infestation.
Humidity Tip #4: Set the Plant on a Pebble Tray
This is an inexpensive and low-maintenance tool for providing a little extra humidity to your Calathea. You can make a pebble tray – sometimes called a humidity tray – out of pretty much any low-sided, flat-bottomed dish. Fill it with gravel, decorative rocks, or something similar. Then add some water to the bottom. Make sure the water isn’t reaching the tops of the pebbles.
Then place your Calathea’s pot on top of the rocks. The water will slowly turn into vapor and waft right up to the plant’s leaves, while the pebbles keep the bottom of the container elevated above the water (your Calathea could develop root rot if you leave it sitting right in a puddle).
A pebble tray won’t have nearly as much impact as an electric humidifier, but it costs hardly anything, and it’s easy to make. The effects will be more pronounced if you have several houseplants on humidity trays clustered near each other.
Humidity Tip #5: Cover it Up
If you’re really struggling to provide enough humidity for your Calathea, you can enclose it in a barrier of transparent material such as plastic or glass. This will trap moisture while letting in the nourishing rays of the sun.
The simplest version of this method is popping a clear plastic bag over the foliage. You’re probably not going to want to keep this up for long stretches since it defeats the purpose of having a beautiful ornamental plant in your home. But bagging your Calathea is a good way to give it some extra humidity while it’s recovering from transplant shock or root division.
A more advanced, long-term method is to grow your plant in a terrarium. You can use just about any enclosed container made of glass or clear plastic, though Calatheas get large enough that a good-sized home aquarium tank is probably your best bet.
Don’t put soil directly in the bottom of the terrarium – this is terrible for drainage. Keep your Calathea in a pot and put the whole setup under glass.
You can line the bottom of the tank with cool-looking rocks, glass beads, or other inorganic material. Try sprucing it up with things like fossils, decorative mosses, dried branches, or anything else you can think of. With a bit of imagination, you should be able to create a unique and attractive display.
If it starts looking too damp inside, you can pop open the lid for a few minutes to let the terrarium air out. Do this if you notice huge beads of condensation forming on the walls, or if the surface of the potting mix is remaining damp for more than 4 or 5 days after you water.
What About Misting?
Some Calathea owners are big advocates of misting your plant regularly with a spray bottle, saying that it boosts the humidity around your plant. And it does – for a minute or two. Then the tiny layer of water you’ve laid down will finish dissipating, and the humidity will return to precisely where it was before.
Test it yourself with a hygrometer if you don’t believe us. You’d have to mist every hour or two to have any noticeable effect on the moisture levels around your Calathea.
On the other hand, just because misting doesn’t do much for humidity doesn’t mean it’s completely useless. There’s some reason to think that a daily spritzing will make your plant a less hospitable environment for spider mites. Since these hungry little bugs are common Calathea pests, anything that encourages them to stay away is good in our book.
You might also find that misting is a good way to schedule some one-on-one time with your plant. This helps you stay attentive to the condition of its leaves, stems, and soil, making it easier to spot any developing problems before they get out of hand.
If you’re going to mist, we recommend using lukewarm water and the finest droplet setting your spray bottle has. See our article on Calatheas and misting for a more detailed guide.
Now that you know how to provide a more humid home for your Calathea, you should be able to keep its leaves looking vibrant and fresh. Remember that many of the tricks above can be combined to enhance their effects! Try using a couple of them at once. Pretty soon, your Calathea will be happily basking in the moist air it loves.