How to increase humidity in air for houseplants

Begonia leaves with drops of water on them

Many houseplants come from tropical areas where air moisture levels are very high. In apartments and homes, increase air moisture to make it more humid with a few simple tricks!

Tropical plants have an advantage over temperate-climate plants because they’re used to growing in temperatures that are high all year-round. This makes them a good match for homes, offices and apartments which are heated in winter for our comfort.

However, indoor air in winter in temperate climates usually is very dry. For tropical plants, providing moisture in the air is a sure way to ensure their survival!

How to increase air moisture around plants

Avoid drafts and corridors

A plant set in a corridor, an entrance, or a place where drafts often occur will dry out faster. This is because the air around them is constantly renewed.

  • A plant tends to create moisture around itself through different processes.
  • For example, transpiration occurs naturally (akin to sweating). Another process that releases moisture is guttation.
  • If the air circulates too much around the plant, this moisture is swept away. Plants dry out much faster.

If possible, try to set your plants in a corner. You can also set a tall shelf nearby to act as a windbreaker.

Some rooms in the house are more moist than others. For instance, many plants will grow well in a bathroom or kitchen if natural light is available there.

Best, however, is to group your plants together, as described below.

Bring your plants together to raise air moisture

Plants grouped together to share the moisture they release.It makes perfect sense to group plants together to create a tiny indoor jungle. Tall plants, short plants, and pots of all sizes will create an oasis of moisture if you set them together.

  • Setting plants together also blocks drafts of wind.
  • Moisture released by plants will be absorbed by their neighbors and not lost.
  • Plants on the inside are more protected from drying out than plants on the outside.

Some plants release a lot of moisture in the air. Be sure to include at least one of them in the “oasis of moisture” you’re planning!

Note anything special about these moisture-sharing plants? They’re prone to developing brown tips. Brown tips is a sign that leaves release moisture into the air faster than roots can replenish it! That’s how good they are at sharing moisture to the air around them, especially in dry air…

Lastly, feel free to set up your cutting station right in the middle of your plant oasis. Perfect for starting cuttings and sharing moisture, too!

Clay pebbles in a tray

A cheap but very effective solution is to set a tray of wet clay balls near or under your plant pots.

Rest all your pots atop such a tray and you’ll see them thrive in no time!

Use rainwater for houseplants or, if not, demineralized water like the one used for ironing clothes.

Misting and spraying

If it’s possible for you to tend to your plants often in passing, a great solution is to mist the plants. Use a simple handspray for that.

  • Elaborate bonsai misters produce a finer “cloud”, but a basic plastic squirt bottle does the job just as well.
  • Catch excess water at the back of the plant with a light tray or plastic place-mat. This will protect the wall or floor from dripping water.
  • Use rainwater, or distilled water. Normal tap water will lead to mineral buildup on leaves, inducing leaf burn and brown spots.

Best is to mist two to three times a day – at mealtimes, for instance. But even just a few mistings a week will already be a big help.

This solution, combined with the clay pebbles, is perfect for most houseplants.

Fogger and mist maker devices

A fogging device to increase air moistureA variation is to set up a fogger or a mist-maker right near your plants. This is a device set just below the water surface in a bowl or tray. It vibrates with ultrasound frequency and sends tiny droplets of water in the air, forming a cloud.

  • The most basic version is a single-cell fogger that you place in a wide bowl.
  • Once you get the hang of how it works, you can design a nice fountain-like setting to let the fog cascade around your plants.
  • A single-cell fogger will vaporize about a quart of water per hour (one half liter).
  • Such a fogger will raise moisture within about three to five feet around it (1 to 1.5 meters).
  • Again, use rainwater or distilled water, or you’ll risk clogging the device.

The trick is to ensure the level stays the same relatively to the active part of the device. Too deep, and it won’t mist. Too shallow and it’ll dry out and stop misting, too.

  • One technique is to attach the cell to a styrofoam floater that keeps it immersed at just the right height.
  • Another technique is to control the water level. A notched bottle, filled and secured upside down, will release water as soon as a bubble works its way through the notch. Many bird and animal watering devices work like this, and it’s also a great tip for watering plants when away.
  • Lastly, you can combine this with a fountain that cycles water. Place it in an intermediate level with water coming from above and flowing out.

Recycle – often, essential oil dispensers and nebulizers do exactly the same thing. Check around the neighborhood to see if anybody might have an old one they’re not using anymore. Repurpose it into a small-scale air moisturizer!

Heavy duty solutions – air moisturizers

When you’ve got more than just a few plants to care for, it may make sense to invest in an air moisturizer. These machines aim to raise moisture levels of an entire room and even house.

  • The entire house will be affected by these machines.
  • Smaller units are about the size of a microwave oven.
  • You can set the desired moisture level in the settings.
  • Choose your unit based on the size of the main room you want to moisturize. For instance, a small unit will succeed in moisturizing a room that’s 100 sq feet (9 or 10 square meters).

There are a few precautions, though.

  • Excess moisture might lead to mildew or fungus on walls.
  • Be wary of moisturizing a room with carpet, drapes, and other textiles that might not cope well.

A great option is to set your plants in a greenhouse or lean-in that is designed to deal with high moisture levels.

  • At a smaller scale, you can replicate this by creating a terrarium! Any moisture will be locked in. No more watering, perfect moisture maintained!

Why indoor plants need high air humidity

High air moisture, common in the tropics

Most of our indoor plants actually come from tropical areas. This is because tropical plants don’t need to experience a cold season every year.

Tropical plants are perfectly content with constant, warm temperatures all year round, exactly like the inside of a home or apartment.

Many tropical plants have evolved to cope with extreme climate settings. Tropical climates often alternate brutal monsoon-like rains and desert-like dry seasons.

Techniques plants use to collect moisture and water in the wild

Orchid roots benefit from high air moistureDragon plants like the Dracaena marginata and other Dracaena species have learned to make the most of every drop.

  • Their root system is good at absorbing water from flash floods. Leaves also excel at absorbing air moisture directly.
  • Read also: dragon plant watering schedule derives from its native habitat

In other places, like in tropical jungles, orchids and ferns grow on trees in a symbiotic relationship. These only encounter water when it rushes down the trunk and branches since the tall tips of trees catch most of the rainfall.

  • Orchid roots have a special cellulose sheath around them. This swells within seconds to absorb water as it rushes by. It’s exactly the same thing that happens in modern hydrogel crystals!
  • Ferns wrap around the tree and form sponges that absorb water. Staghorn fern, for instance, forms a bowl all around the trunk of the tree it hangs from.

Still other plants have learned to gather water directly from the air through their leaves, like Tillandsa which has almost no roots at all, and other Bromelia flowers.

Measuring air moisture with relative humidity

Normal air moisture in heated homes over winter is around 40 to 50% relative humidity.

  • Tropical plants thrive best when relative humidity reaches 60, 70 and even over 80%.

Many electronic home thermometers also have a “relative humidity” function.

  • Relative humidity is the amount of water vapor that air can hold at its current temperature.
  • For 100% relative humidity at a given temperature, if a little more water vapor is added, dew or condensation would start forming immediately.

Radiators, heaters and air ventilation systems tend to filter water vapor out, which reduces air moisture. In old days, ceramic vessels filled with water were attached to the radiators to counter this problem and release moisture.

Smart tip about increasing air moisture

Ensuring moisture around your plants means you won’t have to follow your watering schedule as strictly. Less stress and easier plant care!

Image credits (edits Gaspard Lorthiois):
CC BY-SA 2.0: F. D. Richards, Home Garden Labs, Quinn Dombrowski