Complete Guide to Use a Humidifier for Houseplants


How to use a humidifier for houseplants

Some of the most popular houseplants are from tropical climates and therefore thrive in areas with high humidity. If the air in your house is dry, such as during the winter months, your plants may benefit from the use of a humidifier.

Compared to misting or using a pebble tray, a humidifier will provide a more constant humidity level for your tropical houseplants.

For best results, run your plants’ humidifier for a few hours every day between sunrise and midday. The humidifier should be in the same room as your humidity-loving plants but not so close to them that moisture starts to condense on the leaves.

When in doubt about your home’s humidity level, use a hygrometer to get an exact measurement. Different plants have different preferred ranges, but most will be happy in a range between 40% and 60% relative humidity.

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Why do Houseplants need a Humidifier?

Except for succulents and cacti, many popular houseplants thrive when there is more moisture in the air. Plants like orchids and aroids (like peace lily and Monstera), just to name a few, are acclimated to a tropical climate. 

Unlike succulents, which store water in their fleshy leaves, these tropical plants are not used to lower humidity. 

There are a couple of ways plants can absorb moisture from their environment, and these methods can vary wildly from one plant to the next, depending on what kind of climate it is from. 

Some Houseplants has Less Robust Root System

The primary way for a plant to absorb water is through its roots in the ground. Plants growing in the desert evolved to have robust root systems to take advantage of any water they can find.

On the other hand, Tropical Plants , don’t really need such robust roots system because where they originated there’s always water everywhere! 

Epiphytic plants have evolved to absorb moisture from the air. This kind of plant usually grows on or up other plants like trees. Some commonly-known epiphytes include orchids, tillandsia (air plants), and monstera.

Some of these houseplants have roots in the soil, some have structural aerial roots, and some may have no roots at all! For this reason, epiphytes need higher humidity to thrive. 

Some Houseplants Has Thin Leaf System

So once plants take up water, where does it go? 

Some complicated biological processes are involved, but the water basically goes up to the leaves, where it is either stored or released into the air. 

Succulents and cacti store the water in their leaves for later when there might not be any water. This makes them very resilient plants. 

Tropical plants do not have anywhere in their leaves to store water because they have never needed to do so with all the humidity and rainfall all the time! Because of how much water is usually present, these plants can release excess water from their leaves in a process called guttation

Leaves have pores called stomata that basically let the plant breathe. They let in carbon dioxide and release water vapor. They can open or close depending on the humidity level. But if they are closed for too long because of dry air, it is as if the plant is holding its breath! 

Which houseplants need humidifier

Indoor environment has less humidity

Okay, now that we understand a little more about how different plants grow in their natural climates, let’s look at the environment inside your home. 

When the weather is warm and pleasant, your home will maintain relative humidity between 40% and 60%, which is good for most houseplants. However, in the winter, with the heater on, that can drop to as low as 10% relative humidity.

In the same way that this dry air can give you dry skin and a scratchy throat, it also causes distress for your tropical plants that require more moisture in the air. 

Misting or Pebble tray is not enough

There is a common theory that misting your plants will help increase the humidity. Unfortunately, it doesn’t really work. Misting your plant’s leaves will increase the humidity slightly for a very short amount of time. For this to be an effective tool, you would have to mist every 30 minutes. 

Additionally, if you mist your plants in bright, direct sunlight, the droplets leftover can act like little magnifying glasses and burn spots on the leaves. Also, too much moisture at night can take too long to evaporate and will act as an open invitation to mold and fungus. No, thank you! 

Misting is a great exercise for your forearms, and that’s about all it’s good for. 

Placing a pebble tray with water near your plants is another common method to increase the relative humidity. They work by introducing water to the area near your plants. Over time, that water evaporates into the air and increases the relative humidity in that area. 

Pebble tray works better than misting, but it is not as effective as using a humidifier. 

When to use a humidifier?

Let’s look at when you should be using a humidifier for your plants. What time of day should you turn it on? How about the season or time of year? How does the room condition come into play? Most importantly, how much humidity is too much? 

When is the best time to turn on humidifier for houseplants: Between 7 am to 12 pm or if the room humidity drop below 40%

Best time to turn it on

The best time to run a humidifier for your plants is in the morning between sunrise and midday. You can turn it on with breakfast and turn it off when you eat lunch. 

This will provide plenty of humidity for your plants!

If your humidity is still a little low after checking it with a hygrometer, you can let the humidifier run a little longer into the afternoon. 

Don’t run it too late into the evening or at night when the sun is down. Too much moisture at night will disrupt your plants’ natural transpiration process (their way of breathing). 

Room condition

Different plants have different ideal humidity ranges in which they are comfortable. You can test the air’s relative humidity in your home using a hygrometer to see if it falls in the right range. 

Usually, if the humidity is below 40%, you will need to run the plants’ humidifier. Once the air reaches over 65% humidity, you can turn off the humidifier. 

Weather & Season

Every location has its own specific climate, but in general, humidity is higher in the summer and very low in the winter. 

Some of this is because of chemistry and physics. Warmer air has the capacity to hold more water vapor, while cooler air cannot hold as much vapor. There is less ambient moisture in the winter because of the cold, and then heating the air in the home makes the relative humidity drop way down. 

You should run a humidifier for your plants in the winter when the air is dry, and in the summer too if you live in a climate with low humidity. 

How much humidity is too much?

Humidity over 80% is excessive for any plant. Too much water vapor in the air can also prevent your plant from being able to “breathe” properly and can also lead to issues such as mold and fungus infestations. 

Too much humidity can be negated by introducing better airflow with a fan and moving the humidifier a few feet away from your plants. 

Some humidifiers come with a built-in humidistat so you can check the relative humidity of the room easily. If yours does not have that function, you should get a hygrometer to double-check your room’s humidity every so often. Your plants will thank you. 

Best Practices for Using Plant Humidifiers

How often should I use a humidifier?

It would be best if you used the humidifier for your plants every day. Use a hygrometer in the morning to check the moisture level in the air. If it is below 40% relative humidity, time to turn on the humidifier! 

As mentioned earlier, this is more likely to be the case in the winter when the temperature drops and the heaters suck up all the extra moisture in your home. You are not likely to need a humidifier for your plants as often in the summer. 

How long do you run a humidifier for plants?

You should run your humidifier for at least 4 to 5 hours every day in the morning until midday. Running it too late into the afternoon risks leaving too much moisture in the air overnight when the plant doesn’t absorb it as much, which increases the risk for mold or fungus. 

Where to place humidifier?

It would help if you placed the humidifier a few feet away from your plants, preferably in the center of the room. Placing it too close to the plants could cause too much water to condense on the leaves and soil. Too much water on the leaves is an invitation for mold and fungus! 

Elevate the humidifier a few feet off the ground on a table or desk. Keep it away from porous surfaces like wood or fabric curtains. These porous surfaces are more likely to develop mold when left in overly wet air. 

Do not place the humidifier on a soft surface like carpet. Many of these devices have air intakes on the bottom, and a carpet or rug would block that area. 

What type of water to use?

The best practice is to use filtered or distilled water in your plants’ humidifier. This will ensure that only pure water is being vaporized into your home. 

Using distilled water will also keep algae and bacteria from growing in the water tank for longer, meaning you won’t have to clean it as frequently. 

If you decide that you want to use tap water in your humidifier, be aware that the minerals can cause a scale buildup in the device over time. Using filtered or distilled water will prevent you from cleaning the device as often and extending the humidifier’s lifetime. 

Regular cleaning for a humidifier

Every so often, you will need to clean your plants’ humidifier. This could be due to mineral buildup from the water or algae and bacteria, which is attracted to moisture. 

If your humidifier doesn’t get cleaned for a long time, there will be a buildup of bacterial gross stuff that you do not want to be spewing into the air in your home!

You should give your humidifier deep cleaning every week. 

First, pour vinegar into the base and let it soak. Then use diluted bleach or peroxide to clean out the water tank to remove any slime or smells. Rinse the parts out with tap water before filling it back up for daily use. 

Some humidifiers have water filters. These will need to be replaced regularly. Each product is different, so you will have to check the specifications of your device. 

Qualities to consider when picking plant humidifier

So how do you go about choosing a humidifier for your plants? There are so many different options that it can be hard to figure out sometimes. 

That’s why I have this handy guide for you. Listed here are all the things you might want to consider before getting a humidifier for your plants. 

Here is what you should look at:

Questions to ask before deciding which Humidifier to buy for houseplants

Some of these factors will be more important for you than others when deciding, but it is important to be well-informed in all considerations. 

Types of humidifiers for plants

There are three main kinds of humidifiers you can get: warm mist, ultrasonic and evaporative. All three of these will work fine for your plants; it’s just a matter of what works best for you as well. 

QualitiesWarm MistUltrasonicEvaporative
How does it work?Heating element evaporates waterVibrating plate creates vaporFan blows vapor from saturated wick
TemperatureWarm mist Cool mistCool mist
Noise levelQuietQuietNot as quiet (fan)
Safety: burnsBurn risk for children and petsNo burn riskNo burn risk
Safety: bacteriaNo bacteria riskMust clean frequently to prevent bacteria riskMust clean frequently to prevent bacteria risk
ElectricityUses moreUses lessUses less
Water filter?NoNoYes

Warm Mist Humidifiers

Warm mist humidifiers work by using a heating unit to bring the water inside up to a boiling temperature, turning the water from a liquid into a vapor. 

Because of the way the mist is created, only pure water leaves the device. Any minerals in the water are left behind in the water tank, and the risk of germs or bacteria is reduced. 

Warm mist humidifiers do not use a fan to propel the water vapor, meaning they are a little quieter than the other two kinds. However, the heating element requires more electricity and can be dangerous for curious kids and pets. 

Ultrasonic Humidifiers

Ultrasonic humidifiers do not use a heating element to turn the water into vapor. Instead, they use a vibrating plate to create a cool mist. 

The lack of heating element means there is a greater chance for bacterial buildup in an ultrasonic humidifier. Also, anything dissolved in the water will be carried with the mist. For this reason, it is always recommended to use filtered or distilled water when using an ultrasonic humidifier. 

Evaporative Humidifiers

Like Ultrasonic humidifiers, Evaporative humidifiers also create a cool mist. However, it is created differently. In this type, there is a filtering wick that absorbs water from the tank. Then, a fan blows over the wick to cause the water to evaporate into the air. This creates an invisible vapor. 

This humidifier is nice because it filters the water as it works, although the fan might be a little noisy. There is also no risk of getting burned from a heating element. 

Evaporative humidifiers are unable to oversaturate the air. If the air already has enough moisture in it, the water simply will not leave the wick due to physics and chemistry principles, no matter how much the fan blows. This is great for folks who might forget to turn off their humidifier. 

You do need to make sure to replace the wick regularly to prevent bacterial buildup. 

Warm vs. Cold Mist: Which do plants love more?

There will not be a big difference for your plants whether you use a warm mist or cool mist humidifier. The warm mist humidifier may warm up your room a little bit, but the effect will be negligible. The ultrasonic humidifier may cause some minor white, powdery buildup in the room, including on your plants, if you do not use distilled water. 

Beyond that, the specifications that matter most have less to do with what kind of mist is produced and more to do with how long the humidifier can run and how big of a room it can service. That’s what we will discuss next!

Grow Room Size

Like any appliance that affects the air in a room, such as a heater or air conditioner, different humidifiers will have a different room volume capacity. If you only have a small shelf of plants, you may only need a small diffuser. But if you have a huge room for your tropical plants, you will need either a powerful humidifier or perhaps two smaller ones. 

The humidifier’s capacity will be listed on the box with the rest of its specifications. They are usually labelled for small room, medium room, or multiple room use. 

Run Time

You wouldn’t want your humidifier to run out of water before it is done providing humidity to your plants! When looking for the best humidifier for your situation, you should look for one with a longer run time, which usually goes hand in hand with a larger water reservoir. 

Noise Level

The noise that your plants’ humidifier makes may or may not matter much to you (your plants certainly won’t know the difference), but it is definitely something worth considering when making a new purchase. 

Evaporative cool mist humidifiers will generally be a little louder due to the fans used to distribute the water vapor. If this would bother you, you may want to go with an ultrasonic cool mist or a warm mist humidifier. 

Large and easy to clean tank system

You will need to clean your humidifier frequently, so you should consider purchasing one that is easy to take apart and clean. 

Too many fiddly parts will discourage you from cleaning it as often as you should, which could lead to nasty things getting in the air. 

A larger tank is also better than a small one as you will not have to refill it as often. Some units have a convenient top-fill design, which makes it very easy to refill. 

Design

The final thing to consider when looking for a humidifier for your plants is its aesthetic design. This is something that will be placed in a noticeable area in your room; you shouldn’t purchase something you don’t want to see! 

My Recommendation for a Good Plant Humidifier

There are many humidifier options out there, so I’ll make it a little easier for you by recommending a couple of my favorites. 

Budget: Pure Guardian H965AR

Best Budget Humidifier for Houseplant: Pure Guardian H965AR

The Pure Guardian H965AR is an ultrasonic cool mist humidifier that costs about USD$ 40, a great option if you are on a budget. This tabletop unit is great for small rooms. It has a one-gallon capacity tank, and the unit shuts off when the tank is empty. 

This is the humidifier I started with for my plants, back when my collection was much smaller! I found that if I ran it only in the mornings, it could go for a few days without needing the tank to be refilled. 

As my plant collection grew, I started to run the humidifier on high and used a fan to spread the moisture through the room. (Without the fan, leaving the humidifier on high would cause too much moisture to accumulate on the soil, and I was worried about mold.) 

At this point, I decided to look for a new humidifier that would work for a bigger space. 

Best Value for the Money: TaoTronics

TaoTronics 4L Ultrasonic Cool Mist

For a little more money, you can get the TaoTronics 4L Ultrasonic Cool Mist Bedroom Humidifier. This one is going for a little over USD$ 50. This model has a built-in humidistat, which you can use to set a preferred relative humidity level for your plant room, at which point the device will shut off automatically. No more oversaturated air! 

The water tank holds over a gallon, and it will last between 12 and 50 hours depending on whether the device is set to low, medium, or high. 

This is the model that I use for my own plants now, and I really love it. Not only is it quiet, but it’s also really easy to clean and refill. The clear plastic tank lets me see when the water is running low so that I can refill it before it runs out, and it even has a little night light! 

The controls are straightforward to use, letting me give my plants the exact amount of humidity that they need. 

There are some more expensive options out there, some going for over USD$ 100. These models usually have larger tanks and can provide humidity to multiple rooms, sometimes the whole home. Unless you plan to turn your home into a jungle, this is an unnecessary expense for your plants! 

Related Questions:

Can I use Oil Diffuser or Regular Humidifier for plants?

You can absolutely use a regular humidifier for your plants; I’ve never seen a humidifier marketed specifically for plants! 

As for the essential oil diffuser, you certainly could use one, although it would not provide as many benefits as a full-size humidifier. Oil diffusers usually have a much smaller water tank capacity and would have to be refilled frequently. The amount of oils released into the air should not be enough to damage your plants unless they are exceptionally delicate. 

Do humidifiers cause mold?

Humidifiers can cause mold if they raise the humidity levels too high or are placed too close to a porous surface like wood. As long as you have enough air movement in the room and keep an eye on the relative humidity with a hygrometer, you should have nothing to worry about. 

Gabriella Anastasia

I have been growing houseplants for most of my life and have been collecting them ever since I was 11 years old.  Now 33, I've always had a green thumb (even though my parents thought otherwise) and love to share my knowledge with others.

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