How to Increase Humidity for Plants: What Actually Works

The Lab | Humidity for Houseplants

Once the heating comes on, indoor air gets dry, often 10 to 20% relative humidity according to Iowa State, and tropical houseplants show it with brown leaf tips, crispy edges and stalled growth. The usual tips (mist your plants, set them on pebbles) are repeated everywhere, but university extension specialists don’t agree that all of them work. This guide covers how to increase humidity for plants: the ideal humidity for houseplants, which methods actually raise it, how to increase humidity for plants without a humidifier, and how to increase humidity for plants in winter without inviting mold. It follows Iowa State, Penn State, UNH Extension and the EPA.

The verdict Many houseplants prefer about 40 to 50% relative humidity, while heated homes in winter can drop to 10 to 20% (Iowa State). A humidifier near your plants is the most reliable fix. Grouping plants helps a little, pebble trays are debated, and misting does almost nothing: Penn State says even daily misting does not raise humidity around a plant. For very humid-loving plants, a terrarium or cloche works best. Keep the room below 60% to avoid mold (EPA).

Ideal Humidity for Houseplants

Source	What it says
Iowa State	Many houseplants prefer 40 to 50% relative humidity; many homes are only 10 to 20% in winter
UNH Extension	Aim for about 40 to 50%; many tropical plants prefer more
Penn State	ASHRAE recommends 30 to 60% indoors; winter heating can push it below 30%; most houseplants do better than a typical heated home provides, cacti and succulents being exceptions
EPA	Keep indoor humidity below 60%, ideally 30 to 50%, to limit mold

Sources: Iowa State Extension FAQ; UNH Extension (Erler 2020); Penn State Extension (Miklas 2024); EPA, A Brief Guide to Mold, Moisture and Your Home.

Put together, a sensible target for a mixed collection is about 40 to 50%: high enough for most tropical foliage plants, and below the 60% ceiling the EPA sets for mold. Measure before you buy anything. A cheap hygrometer tells you what your room really is; Penn State suggests checking with one before counting on a bathroom, for example.

How to Increase Humidity for Plants: Methods Compared

Method	How well it works	What the sources say
Humidifier	Best	“An excellent way” to raise humidity (Iowa State); recommended by UNH; a whole-house unit helps even if it can’t reach ideal levels (Penn State)
Terrarium, cloche or cabinet	Very good, for small plants	Glass covers recycle humidity in the plant’s immediate surroundings (Penn State)
Grouping plants	Some help	Moisture from soil and leaves raises local humidity (Iowa State, UNH); effect depends on how many plants and room size (Penn State)
Pebble tray	Debated	Raises humidity around plants (Iowa State); a practical option (UNH); moisture spreads through the room, so the effect is minimal (Penn State)
Cooler room	Some help	Cooler temperatures raise relative humidity somewhat (UNH)
Bathroom	Depends	Depends on how often the shower runs; bathrooms often lack light (Penn State)
Misting	Little to none	Not effective (Iowa State); even daily misting does nothing for humidity around the plant (Penn State); helps only briefly and can promote fungal problems (UNH)

Sources: Iowa State Extension FAQ; Penn State Extension, Humidity and Houseplants (2024); UNH Extension (2020).

Potted calathea standing on a tray of pebbles and water, with the water below the bottom of the pot — On a pebble tray the pot sits on the stones, above the water line, so the roots never stand in water (Iowa State).

Humidifiers

Every source we checked puts the humidifier first. Iowa State calls it an excellent way to raise relative humidity in the home, and UNH Extension recommends one for winter, while noting it may not fully offset the dry air from a heat register blowing nearby. Penn State says a whole-house humidifier won’t reach ideal levels for plants but still helps, especially with forced hot-air heating, and that portable units are an option.

Put it near the plants, not across the room, and group the plants around it.
Use the hygrometer, not a guess. Run it until the room reads about 40 to 50%, and stay below 60% (EPA).
Watch the windows. The EPA notes that condensation on windows or walls can be a sign of high humidity; wipe it dry and turn the humidifier down.
Keep it clean following the maker’s instructions, since standing water in the tank is where problems start.

How to Increase Humidity for Plants Without a Humidifier

No humidifier? These are the options, from most to least useful:

Put small humidity lovers under glass. A terrarium, a glass cloche or a closed cabinet keeps moisture around the plant (Penn State). This is the best low-cost option for ferns, nerve plants and other small, fussy plants. See our guides on how to make a terrarium and setting up a greenhouse cabinet.
Group your plants. Water evaporating from the potting mix plus water given off by the leaves raises humidity around the group (Iowa State). The more plants, the better; one or two pots won’t change much (Penn State).
Try a pebble tray. Fill a tray or saucer with pebbles and water, and keep the water level below the bottom of the pots (Iowa State) so the roots never sit in water. Treat it as a bonus, not a cure: Penn State says the moisture disperses through the room.
Move plants away from heat. UNH says heat registers blow hot, dry air: keep tropical foliage plants away from them, and leave the spots near heat to succulents.
Use the right room. A bright bathroom with a regularly used shower can work, but measure it first (Penn State). See our guide to bathroom plants.

Does Misting Work?

Not for humidity. Penn State says the boost lasts only until the water evaporates, often a few minutes, and that “even daily misting does nothing to raise the humidity levels around a plant.” Iowa State adds that you would have to mist several times a day, which is impractical, and UNH warns that misting can promote fungal problems. The exception is air plants (Tillandsia), for which Penn State says misting is an accepted way to water; see our air plant care guide.

Don’t overdo it More humidity is not always better for your home. The EPA recommends keeping indoor humidity below 60%, ideally 30 to 50%, because damp surfaces grow mold. Raise humidity around the plants (glass, grouping) rather than turning the whole house into a greenhouse, and dry any condensation on windows.

How to Increase Humidity for Plants in Winter

Winter is when humidity drops furthest: Iowa State says many homes fall to 10 to 20%, and Penn State notes heating can push humidity below 30%. A winter plan that follows the sources:

Run a humidifier near the plants and check a hygrometer (Iowa State, UNH).
Pull tropical plants away from heat registers and radiators (UNH).
Group plants in the brightest spot you have, since light matters as much as humidity in winter.
Keep plants a few inches from cold glass (UNH), which also keeps them out of the condensation zone.
Water less: UNH notes plants need less water at cooler temperatures, so let the top of the mix dry between waterings.

Penn State’s last word is a useful reality check: light and watering are easier to control than humidity, so get those right first. Our guide to winter houseplant care covers the rest, and for the science of humidity and temperature together, see VPD for indoor plants.

Which Plants Need It Most

Humidity need	Examples	Our guides
High: struggles in dry rooms	Maidenhair fern, nerve plant, calathea, Boston fern	maidenhair fern, nerve plant, calathea, Boston fern
Moderate: most tropical foliage plants	Pothos, philodendron, monstera, dracaena	pothos care, dracaena care
Low: fine in dry air	Cacti and succulents (Penn State)	how to grow succulents

Sources: Penn State Extension (2024) for cacti and succulents; plant groupings follow the sources cited in each of our care guides.

Signs of Too Little (and Too Much) Humidity

Sign	What it can mean	Source
Brown leaf tips and edges	Humidity too low (also check watering and salt buildup)	UNH, Clemson HGIC
Spider mites appearing	They thrive in hot, dry conditions	UGA
Condensation on windows or walls	Humidity too high	EPA
Leaf spots after frequent misting	Wet foliage favoring fungal problems	UNH

Sources: UNH Extension (2020); Clemson HGIC 2251 (2025); UGA Extension B1318 (2022); EPA.

Brown tips are not always humidity Clemson HGIC lists hot, dry air, improper watering, insect feeding and salt buildup as causes of brown tips and edges. Check the soil and the pot rim for white crust before blaming the air. See our guides to dracaena brown tips, white crust on houseplant soil and getting rid of spider mites.

Key takeaway How to increase humidity for plants: aim for about 40 to 50% (Iowa State, UNH), measure with a hygrometer, and use a humidifier near your plants as the main fix. Without a humidifier, put small humidity lovers under glass, group plants and keep them away from heat registers; pebble trays are a debated bonus, and misting barely works (Penn State, Iowa State). Keep the room below 60% to avoid mold (EPA).

Frequently Asked Questions

How do you increase humidity for plants?

Use a humidifier near your plants; it is the most reliable method according to Iowa State, UNH and Penn State. Grouping plants, glass covers and pebble trays add a little more.

What is the ideal humidity for houseplants?

Many houseplants prefer about 40 to 50% relative humidity (Iowa State, UNH). Keep it below 60% to limit mold (EPA). Cacti and succulents are fine in drier air (Penn State).

How can I increase humidity for plants without a humidifier?

Put small plants under a cloche or in a terrarium, group plants together, keep them away from heat registers, and try a pebble tray with the water below the pot bottoms (Penn State, Iowa State, UNH).

Does misting plants increase humidity?

Barely. Penn State says even daily misting does nothing to raise humidity around a plant, because the water evaporates in minutes, and UNH says it can promote fungal problems.

Do pebble trays work?

The sources disagree. Iowa State says water evaporating from the tray raises humidity around the plants; Penn State says the moisture spreads through the room, so the effect is minimal.

How do you increase humidity for plants in winter?

Run a humidifier near the plants, move tropical plants away from heat registers, group them, and check humidity with a hygrometer. Winter homes can drop to 10 to 20% (Iowa State).

Can humidity be too high for houseplants?

For your home, yes. The EPA recommends staying below 60%, ideally 30 to 50%, to prevent mold, and condensation on windows is a sign humidity is too high.