As we’ve grown more enthusiastic about caring for our tropical houseplants, many of us have looked for ways to increase humidity indoors.
While the average household humidity is 30-40%, most of our houseplants are native to tropical regions where the humidity is 77-88%. Fortunately, these tropical houseplants don’t require levels this high to thrive in our homes, but they do need supplemental humidity.
Providing higher indoor humidity for houseplants also offers numerous health benefits for your plants.
Why is Humidity Important for Indoor Plants?
Do our houseplants really need humidity?
Yes, tropical plants with generally large, thin leaves need moisture in the air. Indoor plants grow best under conditions most similar to their native habitats. Therefore, we want to replicate their natural environment to the best of our abilities indoors.
When tropical plants are given adequate humidity, they have fewer health issues and can thrive indoors.
Benefits of providing high humidity for tropical plants
- Accelerated growth
- Fewer occurrences of new leaves becoming stuck
- Avoid crispy leaves and leaf drop
- Pest deterrent
- Increased drought tolerance
- Stronger plants with improved immunity to disease
The Science of How Humidity Affects Plant Growth
It may surprise you that humidity is needed during photosynthesis for tropical and subtropical plants.
During photosynthesis, plants absorb CO2 through pores on their leaves called stomata. These pores allow plants to exchange carbon dioxide (CO2) and water with the atmosphere, expelling excess moisture as needed. For most tropical plants, the stomata should be open during the day and closed at night.
However, the stomata are encased in guard cells that will close when they sense that the ambient moisture is too low, such as with low humidity. This is the plant’s defense to protect it from losing too much moisture. Since tropical plants are adapted to higher humidity, their guard cells are sensitive to drops in humidity.
When the stomata are closed, the plant cannot take in CO2 to complete photosynthesis. Therefore, adequate humidity (at least 50%) will ensure that your tropical and subtropical indoor plants properly synthesize food and grow.
By understanding the science behind this process, we realize why humidity is vital for the growth of tropical houseplants.
Which Houseplants Require High Humidity?
Some tropical indoor plants will thrive with increased humidity but don’t rely on it for survival. However, other tropical houseplants will decline quickly without it.
You can always find a plant’s humidity requirements by researching the plant and comparing several trusted resources for a reliable answer. Often, plants native to rainforests with thin or fuzzy leaves need humidity to remain healthy.
The following is a general but not all-inclusive list of common houseplants requiring high humidity.
Plants that Need High Humidity (at least 50%)
- Peace Lilies
- Creeping figs (Ficus pumila)
- Polka dot plants
- Zebra Plants (Aphelandra squarrosa)
- Coffee Plant
- Scindapsus Pictus Jade Satin (a less common variety of Scindapsus)
- Ming Aralias
- African Violets
Many other houseplants will benefit from elevated humidity without requiring it, such as Pothos, Hoyas, common Scindapsus, and Ponytail Palms.
What Humidity Level is Best for Indoor Plants and People?
Within our homes, we want to aim for a humidity level that keeps our plants happy but is also safe for us.
We can be comfortable and healthy in a 35-60% humidity range. Therefore, a good range of humidity for tropical plants still safe for people is 50-60%, bearing in mind that people with certain health conditions may have different needs.
Also, some rarer tropical plants do better with even higher humidity, between 60-70%. However, this is better maintained in a greenhouse or a small space where people don’t spend their entire day.
Signs of Low Humidity in Houseplant Leaves
When plants do not receive adequate humidity, they may show the following signs of stress in their leaves:
- Damaged new leaves
- Easily scorched by sunlight
- Brown spots or tips
How To Help Plants Struggling With Low Humidity
If you have a plant that has become stressed due to a lack of humidity, take the following steps.
- Be diligent with watering. Plants requiring high humidity are susceptible to drought when the humidity is low.
- Increase the humidity of your space or move the plant into a cloche, terrarium, or greenhouse cabinet.
- Provide warm temperatures along with supplemental humidity. A warm, moist environment gives the tropical plant the ideal conditions while recovering.
Warm air holds moisture better, and the ideal temperature range for a recovering tropical plant is between 70-80 degrees. So, if you usually keep your home cooler, move your stressed plant into a warmer room such as the bathroom.
- Remove your plant from a high-sunlight environment while it is stressed. Your houseplant will be more prone to sun-scorching while its leaves are dry.
- Check thoroughly for pests since they thrive in dry air. While pests can infest your plants at any time, their populations can spread more quickly and get out of hand in dry air. Pests are also more likely to attack weakened plants. Therefore, you should check your stressed plant thoroughly for pests.
If you locate pests on your houseplant, try manual removal with a gentle water rinse while the plant is stressed. Once your plant’s condition improves, it will then be able to handle the application of a pest treatment such as neem oil.
Use a Humidifier – The Best Way to Increase Humidity for Indoor Plants
Humidifiers are the best way to ensure that your tropical houseplants receive adequate humidity.
Using a humidifier is superior to other methods because it provides constant humidity for the entire space. Furthermore, many humidifiers have built-in features such as hygrometers, thermometers, and humidity control.
A variety of humidifiers are available, and just about every plant enthusiast has a favorite. Purchasing a humidifier comes down to your space, the requirements of your plants, and your preferences.
Things to Consider when Choosing a Houseplant Humidifier
- Size of your space
- How often you’ll be able to fill it
- Level of humidity you need to add
Best Features to Look for in a Humidifier for Plants
- Hygrometer: measures the room’s humidity
- Target humidity percent & control: more than simply measuring, this lets you control the humidity.
- Smart Device: not required but certainly convenient to control humidity from your smartphone.
- Top Fill: another highly convenient feature since you’ll fill it often
- Run time of at least 12 hours.
Author Tip: Since I kept my plants in a small space and wanted all these features, I went with this 3L Levoit. I’ve been very happy with it for a year now. However, if you need to humidify over 290 square feet, I recommend using a larger one, so you won’t have to fill it too often.
7 Ways to Increase Humidity for Your Plants Without a Humidifier
1. Mist Your Plants
You may have heard of the debate on the concept of misting. Plant enthusiasts often argue about whether misting your plants does anything to increase the humidity. The best consensus is that misting your plants can temporarily provide supplemental humidity. This is still better than no added humidity.
By using fine mist, you are adding moisture to the air. However, this moisture will evaporate and be partially absorbed by your plant.
Misting your plants has been shown to provide a 10% increase in humidity, lasting approximately fifteen minutes.
This is a handy solution if you are limited on time and want to quickly create a small humidity boost. While quick and simple, this increase won’t last very long.
Consider these factors when misting houseplants:
- Some plants don’t respond well to moisture on their leaves, such as the Alocasia Black Velvet, African Violet, and Philodendron Micans. Often, plants with velvety leaves are sensitive to moisture on their leaves. For these plants, use a different method for adding humidity.
- If you are regularly misting, ensure you have proper air circulation to encourage evaporation. This will help prevent mold.
2. Keep Plants Near Fountains or Containers of Water
Another way to increase humidity is to keep water near your plants. For example, you can place jars or bowls of water by your plants, increasing the air humidity slightly as the water evaporates. Additionally, fountains are a good option since they are aesthetic and release moisture into the air with the constant flow of water.
3. Use a Terrarium, Cloche, or Greenhouse Cabinet
You can create greenhouse humidity by keeping your houseplants in an indoor enclosure. Thanks to the houseplant community, there are many purchasing options for indoor greenhouses and terrariums. For smaller plants, you can use a cloche to cover and enclose the plant. These enclosures retain moisture and condensation, keeping the humidity high for your houseplants.
4. Group Your Houseplants Together
Create a humid microclimate by grouping your plants closely. In the process of transpiration, plants release moisture through their leaves. Therefore, grouped plants will benefit from one another by absorbing and releasing humidity. This helps mimic their natural habitat.
5. Use a Pebble Tray
A pebble tray is a shallow dish filled with pebbles and water that can increase humidity. An experiment found that this method can increase the humidity by 2-3% for each plant.
When you place your houseplant on top of a pebble tray, the pebbles provide a barrier between the plant pot and the water reservoir. Therefore, the idea is for indoor plants to benefit from moisture in the air released from the pebble tray without sitting in water.
Since pebble trays are shallow, they don’t require much water and are easy to keep filled. Because this method does not increase humidity significantly, it is more effective when combined with another method.
How to Make a Pebble Tray
- Use a shallow glass or ceramic tray. You may also consider using a terracotta saucer. However, if using a terracotta saucer, place a waterproof barrier under it to prevent damage to your surfaces. Terracotta absorbs moisture and will also release it onto surfaces.
- Fill the tray with small decorative rocks or pebbles.
- Add water to the tray until it reaches a level just below the tops of the pebbles.
- Place your houseplant on top of the pebble tray. Fill the water as needed every 2-4 days. Wash the tray and rocks with mild soapy water once weekly and rinse thoroughly.
FURTHER READING: How To Make A Pebble Tray For Plants (To Increase Humidity)
6. Keep your Houseplants near a Sink or Shower
If you have good natural light in your bathroom, this could be an excellent place for your humidity-loving tropical plants.
The shower or bath creates a humid environment, and the bathroom tends to maintain slightly higher humidity than the rest of the home. Additionally, your kitchen sink can be a humid place with the frequency of hot running water.
Keep pet safety in mind if they can reach any of these locations. Many of our beautiful tropical plants are toxic to pets. Hanging your tropical plant above the kitchen sink or near the shower could work best for pet safety.
7. Place Your Plants Near Your Fish Aquariums
Combining houseplants and fish aquariums in a space creates a beautiful oasis. Set your tropical plants on top of your aquariums or hang them nearby. The water in your aquariums and flowing through the filters will create additional humidity in your space.
The Importance of a Hygrometer
In conclusion, we highly recommend a hygrometer for your plant space. Digital hygrometers are inexpensive and relatively accurate, with only a 3% margin of error.
Knowing your indoor humidity will help you determine if methods are working in your space, and you’ll know when the humidity is too low or high. This information will be very helpful as the seasons change, and you’ll be able to adjust accordingly.