Many of our popular houseplants originate in tropical regions, so they like warmth (usually above 7°C) and humidity.
However, in winter, when we turn on the heating, the air in our homes often gets very dry, and this can cause their leaves to turn brown or shrivel, especially around the edges and tips. This lack of humidity also encourages infestations of red spider mite, which feed on sap, leaving yellow mottling on the leaves and weakening the plant.
Most indoor plants suffer in dry air, but species with thin leaves are at greatest risk. If you grow indoor ferns such as the maidenhair fern (Adiantum raddianum), palms such as Chamaedorea elegans, or prayer plants (Calathea, Maranta), then check them regularly over winter and follow our tips to keep them healthy.
Discover how to raise humidity for houseplants, below.
Avoid hot spots and draughts
Don’t stand house plants near radiators and other heat sources. Not only will any leaves that touch a heater get scorched, but humidity will also be at its lowest. If you have underfloor heating, raise large plants off the ground and onto a small table or plant stand. Don’t place plants near doorways or corridors, as draughts lower humidity.
Spray with water
The easiest way to increase air humidity is to spray plants with a fine mist of water. Try to use rainwater, which doesn’t contain chemicals or lime, and make sure it’s tepid before spraying. It’s best to move plants to a sink or bath when misting them, as moisture can damage wooden furniture and soft furnishings.
Stand plants on gravel
If you stand plants in a gravel tray, this creates a damp microclimate and, as the water evaporates, the humidity increases. Choose a large tray or shallow ceramic bowl, add a layer of gravel and stand the plants on top. Water it to keep the gravel moist, but not so much that you can see the water, then top it up regularly.
Use the bathroom
Hot showers and steaming baths create a naturally humid environment in the bathroom, making it the ideal location for growing the more delicate exotic plants. Consider moving ferns and other plants into the bathroom, especially during the winter, and they should thrive without the need for supplementary misting.
Grow under glass
For delicate plants you want to protect over winter, consider putting them in a terrarium. These glass containers trap moisture, forming a humid environment. Use a second-hand aquarium, or a large glass jar with a lid for smaller plants. Water once when the plant goes in, and you shouldn’t need to water again for several months.
Feature by Dr Ross Bayton