Skip to content

Humidity

Also known as Relative humidity, Raising humidity for houseplants

Growing know-howDepends
Ferns in a lit terrarium, which keeps humidity high Photo: Netha Hussain · CC BY 4.0

In short

Many tropical houseplants come from humid places and suffer in dry indoor air, especially in heated or air-conditioned rooms. Humidifiers, grouping plants, pebble trays and enclosures help; misting raises humidity only for minutes.

How it looks

Relative humidity is the percentage of water vapour the air holds compared with its maximum at that temperature. Nebraska Extension notes about 30–50% is recommended for people, while many houseplants prefer much higher levels, around 70–80%. A cheap hygrometer shows the real figure.

Signs

Low humidity: drying and browning of leaf tips and edges. Frequent misting keeps leaves wet and can encourage disease.

What favours it

Heating dries indoor air sharply, and air-conditioned rooms can be dry even in humid climates.

Prevention

  • Choose plants that match your air: cacti, succulents, cast iron plant, Chinese evergreen, pothos, philodendrons and dracaenas tolerate drier rooms; ferns, calatheas, marantas and rex begonias need more humidity.
  • Use a humidifier; Nebraska Extension mentions one installed on the home heating and cooling system.
  • Group plants together so their transpiration creates a slightly more humid pocket.
  • Stand pots on a tray of pebbles and water, with the pot resting on the pebbles, not in the water.
  • Grow very humidity-demanding plants under a cloche or bell jar, or in a naturally more humid room such as a bathroom or kitchen with enough light.
  • Keep plants away from heaters and air-conditioning vents.

Treatment

Start with the first step and move down only if the problem persists.

  1. Trim brown tips if desired; they will not recover.
  2. Raise humidity with the methods above and check for spider mites.

Pros and cons

Pros

  • Higher humidity lets delicate tropical foliage develop fully and reduces tip browning.

Cons

  • Misting is largely ineffective: Missouri IPM notes it raises humidity for only about 20 minutes, and wet leaves can encourage disease.

Look-alikes

Low-humidity damage
The physiological damage itself: brown, crisp tips and margins.
Salt and fertiliser burn
Also causes brown tips; check feeding and flush the mix.
Underwatering
Dry mix and wilting point to thirst rather than dry air.

Typical uses

Ferns, calatheas, marantas, rex begonias and orchids.

Sources

  1. Success with Houseplants – Humidity — Nebraska Extension in Lancaster County
  2. Gardening myths — Missouri Environment and Garden, University of Missouri IPM
  3. Beautiful winter houseplants and care tips — RHS

Written in our own words from these sources. Check a product label before using any treatment.