If you live in an arid climate, humidity levels will likely be an aspect of plant care that needs your attention.
One reason for this is that the typical American home has ~30% humidity. On the other hand, the average houseplant needs ~60% humidity to thrive!
What can we do to bridge the “humidity gap”? In this article, we’ll cover:
- why humidity is an essential part of plant care; and
- how to raise humidity levels in your home.
What is humidity?
Have you ever felt hot and sticky, and no matter what you did, you couldn’t seem to dry off? If so, you were likely in a place with high humidity.
Humidity is a measure of water vapour levels in the air. When humidity is high, evaporation rates are low, making it harder for sweat to disappear! In houseplants, high humidity helps plants readily retain moisture in their stems and leaves.
When expressed in percentage terms, humidity refers to the amount of water vapour present relative to the maximum level possible at that same temperature. The higher the humidity, the more moisture-saturated the air.
Why is humidity important for houseplants?
As mentioned, most houseplants require an average humidity level of ~60%. This number is simply a reflection of the water vapour levels in their natural habitat. As with all aspects of plant care, deviating from conditions plants have adapted to over several hundred years leads to poor growth.
Succulents are the outliers when it comes to this aspect of care. They readily grow in ~30% humidity levels. Some can even survive dips to 20%!
Being native to desert regions, it’s no surprise that these hardy plants can survive dry conditions.
On the other hand, tropical plants love high humidity levels of 70-90%. In particular, plants native to rainforests thrive at the higher end of this range. Some examples are of tropical plants that enjoy high water vapour levels are Pothos N’Joy; Aglaonema Pictum Tricolor; Monstera Pinnatipartita.
Some common signs that the air is too dry are browning leaf edges or wilting and drooping leaves. Yellowing or dropping leaves are some other symptoms. However, many plant problems, such as underwatering and overwatering, share similar symptoms.
How can we raise humidity levels?
Because of the “humidity gap”, the quest to raise moisture levels is a common one!
There are several ways to achieve this. If you are on a budget, we recommend using options 1 and 2 together, and if you can, options 1, 2 and 3. Taken alone, each option 1 through 3 will not raise humidity levels significantly, which is why you should look at several options at once. We estimate these combined efforts will allow you to raise humidity by up to ~15% with some effort.
However, if you’re looking for a convenient and effective solution, investing in a humidifier (Option 4) is your best bet. If you have several houseplants, the investment is worth it!
Option 1: Use a Pebble Tray
Using a pebble tray is a popular and inexpensive way to increase humidity. Here’s how:
- Fill a shallow tray with pebbles, small rocks or LECA. Any low dish will do.
- Fill the dish with water until the stones are about half-submerged.
- Place your plant on top of the tray.
- Double-check that the bottom of your pot is not in direct contact with water, which invites root rot.
- Refill the water in the pebble tray when you see that all the water has evaporated. Do this preferably in the morning so that evaporation can occur throughout the day.
When set up, the water droplets will cling to the surfaces of the stones and evaporate. This increases moisture in the surrounding air.
While inexpensive and easy to do, this method may be a little time-consuming if you intend on using pebble trays for several different plants.
Option 2: Group Plants together
This one is an easy win! Grouping plants together is the easiest way to increase moisture in the air.
When plants transpire, their stomata open, and water evaporates from the surfaces of their leaves. This increases the level of water vapour directly around the plant.
When houseplants are grouped together, they can benefit from higher moisture levels as each plant transpires.
The downside is that this increase in humidity is not significant. That’s why we recommend grouping plants together in parallel to using a pebble tray.
Option 3: Place Plants in the Bathroom
Placing your plants in the bathroom is also an option. Humidity in bathrooms is naturally higher due to water and moist surfaces.
The critical consideration, in this case, would be whether your plant’s light requirements can still be met in the bathroom. Another concern is whether you want your plant in the bathroom or prefer it to be in other living spaces!
Opton 4: Use a Humidifier
Humidifiers are the most convenient and effective option to increase humidity levels. They make for great gifts too!
These devices add moisture to the air by using a filter system to turn water into mist or steam. All you need to do is place your humidifier next to your tropical houseplants and dial-in your humidifier to your preferred setting. Most humidifiers do require some weekly cleaning and changing water.
Personally, our recommendation for smaller spaces of up to 250 square feet is to use the Pure Enrichment MistAire humidifier. We like the quiet effectiveness of this compact, no-frills option.
However, for ultimate convenience and larger spaces, definitely choose the Levoit 6L Warm and Cool Mist Ultrasonic Air Vaporizer, which we think is the Rolls Royce of humidifiers haha. We love the ability to set your required humidity level (i.e, 60% humidity) so there is no guessing required as seasons change. Using its large water tank is convenient as one tank lasts for several days.
Our only caution is that it is pricey!
Bonus option: Place Plants Terrarium or Greenhouse
A left-field option is placing your plant in a greenhouse. If you have the space and budget to build a greenhouse, amazing! We are all jealous.
Greenhouses act as a stabilising environment that buffers your plants from changes in climate and temperature. The glass traps heat and light, creating a warm and bright environment for your plants to grow.
With several plants grouped together in this micro-climate, humidity levels increase. In addition, warmer greenhouse air naturally holds more moisture.
For those of us not quite able to do this (sorry city dwellers!), another option is to create a miniature greenhouse of your own: a terrarium. Of course, this downside is that only a few small plants are suitable for being kept in a terrarium.
Slow-growing, low maintenance plants also work best. Some examples are:
In this article, we’ve explained how humidity is an essential part of plant care. Yellowing, crispy leaves are a common sign that your plant suffers from too-dry air. Some key ways to increase humidity are using a pebble tray, grouping plants together or placing your plant in a bathroom.
However, the most convenient and practical option is investing in a humidifier.
If you’re not sure about the ideal humidity level required for your plant, consult our plant guides. There, you’ll find our advice for all aspects of care needed for your plant to thrive.
Deborah is a plant enthusiast and founder of Gardening Collective.