Houseplants and air conditioning: keeping plants happy in a cool, dry Dubai home

Houseplants come from warm, humid places. A Dubai flat is cool, closed and dry, and the AC runs for months. An interview study of 26 Dubai residents found AC typically switched on continuously through summer, often from May or June to October, with windows opened only for short spells (Murtagh et al., Buildings & Cities). Plants cope with that better than you might expect, if you manage three things: where they sit in relation to the vents, how you water, and the dryness of the air around their leaves.

What cool, dry air does to a houseplant#

The first sign is usually brown, crispy leaf tips and edges. Iowa State Extension links brown tips to low humidity and to over-fertilising, and the RHS says that for calathea the browning of tips and edges is usually the result of low humidity. In a dry room, a heavy hand with the fertiliser makes it worse.

The second sign is pests. Spider mites thrive in hot, dry conditions (Colorado State Extension). Look for a fine pale mottling on the upper leaf surface, then dull, grey or bronzed leaves and, in a bad case, fine webbing (RHS). They are easy to miss until the plant looks tired, so check the undersides of leaves every week.

How dry is your flat? We don't quote a Dubai figure. The retailer numbers we found disagree with each other and none was measured, and your own room depends on the unit, the flat and how often the doors open. A cheap hygrometer will tell you yours. For a home, the US EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%, to limit mould.

Vents, draughts and glass#

A cool room is rarely the problem. Moving air is. Most houseplants are comfortable at the temperatures people are: the RHS gives 16–21 °C for calathea and 19–30 °C by day for moth orchids, and NC State Extension says alocasia should not drop below about 15.6 °C. The same Dubai study found some residents setting the AC to 18–21 °C, which is still workable. Vent air is colder than the room, and cold air blowing across leaves is what damages them. NC State notes that a fiddle-leaf fig can drop leaves from temperature swings near heating or cooling vents, and that rubber plants lose leaves in cold draughts.

• Keep plants out of the direct airflow. If you can feel moving air at leaf height, or a strip of tissue flutters there, move the plant. We don't give a distance in metres because airflow differs between wall units, ceiling units and ducted vents.
• Do not stand a plant under a vent, in line with a wall unit, or in front of a floor-level outlet.
• Watch the glass. West-facing windows are the hot spot in the afternoon, and NC State advises protecting fiddle-leaf figs and rubber plants from afternoon sun.
• Give calathea, alocasia and ferns the calmest corner: still air, bright light, no direct sun. NC State describes prayer plant (maranta) as intolerant of cold draughts.

Cool rooms are often dim rooms. Low-E glass cuts roughly 5–10% of visible light (Melinda Myers), and heavier tint cuts more. If a plant stretches and pales, light is a likelier cause than the AC. Keep the glass and the leaves clean, and see our low-light plants guide for corners that stay dim.

Which plants cope with dry AC air#

Thick, waxy or water-storing leaves shrug off dry air. Thin, patterned or fern-like tropical leaves do not. NC State rates ponytail palm as tolerating heated, dry indoor air exceptionally well, snake plant as tolerating low humidity, parlour palm as doing well in the dry air of interiors, and lady palm as having low humidity requirements. ZZ plant and cast iron plant are both drought tolerant.

Cope well with dry air

ZZ plant

ZZ plant

Zamioculcas zamiifolia

Low–BrightNot pet-safe

Snake plant

Snake plant

Dracaena trifasciata

Low–BrightNot pet-safe

Ponytail palm

Ponytail palm

Beaucarnea recurvata

Bright–SunPet-safe

Parlour palm

Parlour palm

Chamaedorea elegans

Low–BrightPet-safe

Cast iron plant

Cast iron plant

Aspidistra elatior

Low–MediumPet-safe

Lady palm

Lady palm

Rhapis excelsa

Low–BrightPet-safe

At the other end are the plants that want damp air. NC State says Boston fern asks for high humidity and can get scale or spider mites if the air is too dry, maranta needs a humidified room, and nerve plant shrivels and drops leaves in dry air, though it recovers after a drink. Alocasia likes warmth and high humidity. If you love one of these, give it the calmest corner and a humidifier, or choose a tougher plant.

Need extra help in an AC room

Calathea

Calathea

Goeppertia spp. (syn. Calathea)

Medium–BrightPet-safe

Alocasia

Alocasia

Alocasia × amazonica

BrightNot pet-safe

Boston fern

Boston fern

Nephrolepis exaltata

Medium–BrightPet-safe

Prayer plant

Prayer plant

Maranta leuconeura

Medium–BrightPet-safe

Nerve plant

Nerve plant

Fittonia albivenis

Medium–BrightPet-safe

Humidity: what works and what doesn't#

A humidifier is the only common method that changes the air in a room. The rest are local, or don't work. University of Nebraska–Lincoln Extension is blunt about misting: you would need to mist every few minutes to make any difference to room humidity, and constantly wet leaves encourage disease.

Watering in a cooled room#

Water by touch, not by calendar. University of Maryland Extension advises testing the soil with a finger to about two inches (5 cm): if it is dry, water. Lifting the pot works too, because dry potting mix weighs much less than wet. No fixed number of days suits every pot, plant and room. A plant in a cool room generally uses water more slowly than the same plant in a hot one, so don't carry a garden routine indoors.

• Water until it runs from the drainage holes, then empty the saucer. University of Maryland Extension says never let a houseplant sit in water.
• Flush the pot with plain water every four to six months, using at least twice the pot's volume, and let it drain fully. Dissolved minerals and fertiliser salts build up in the soil, and brown tips are one sign. The steps are in our houseplant problems guide.
• Feed lightly. Over-fertilising browns leaf tips (Iowa State Extension).
• Check by touch even in rooms you rarely use, such as a majlis or guest room. The room's schedule doesn't change what the soil is doing.

Pests that like a dry room#

Spider mites are the pest to expect. Colorado State Extension advises washing the plant repeatedly with a jet of water, and the RHS says raising humidity reduces the risk but won't control them on its own. Mealybugs (white cottony tufts, sticky leaves) and scale (small brown bumps) are removed by hand or with an alcohol swab (Colorado State Extension). Our problems guide has the full routine. Keep new plants apart from the rest for a couple of weeks and look under their leaves first, because mealybugs and scale usually arrive on an infested plant.

A simple routine for an AC home#

1. 1

   Map the airflow

   Stand where the plant would sit and hold up a strip of tissue. If it flutters, that spot is in the airflow.

2. 2

   Move before you buy gadgets

   Shifting a plant out of the airflow and off hot afternoon glass costs nothing, and it fixes more problems than any device.

3. 3

   Read a hygrometer for a week

   If the room sits below 30% and you keep ferns, calathea or alocasia, add a humidifier. If it sits above 60%, ventilate or dehumidify, because the EPA links that range to mould.

4. 4

   Water by touch

   Finger test to 5 cm (2 inches), drain well, empty saucers, flush every four to six months.

5. 5

   Wipe the leaves monthly

   Dust blocks light and reduces photosynthesis (Ohio State Extension). Use a damp cloth for big leaves and a soft brush for fuzzy ones.

6. 6

   Look under the leaves weekly

   Catch mites, mealybugs and scale while they are few.