If the # 1 problem with houseplants during the winter months is giving them enough light, the # 2 problem is to making sure they get enough atmospheric moisture (humidity). The air in our homes becomes incredibly dry during the winter because heating systems remove moisture from the air. The colder it is, the more you heat… and drier the air.
How to tell if your plants are suffering from a lack of air humidity? First, dry air especially affects the plants with thin leaves. Plants with thick, leathery or waxy foliage are relatively resistant to dry air, as are plants with very hairy leaves. They do suffer, but not as obviously as others. Succulents – crassulas, sedum, cacti, etc. – are in this category, as are several peperomias and also the rubber plant (Ficus elastica).
Plants With Thin Foliage
Plants with thin foliage – Brugmansia, abutilons, palms, ferns, etc. – suffer most from dry air. Often their leaves curl slightly down, their edges or tip dry out or blacken, they may hang limply even after you water or, most obvious of all, they simply fall off.
Logically, houseplants should need less watering in winter, since they are more or less dormant, but if you need to water as much as during summer or even more, that’s because they are losing a lot of water to transpiration and are not very happy.
A secondary symptom is poor blooming. When the air is dry, flowers dry up, wilt or abort or just don’t last as long as they should, even if the plant itself is relatively resistant to air dry. The thick, hairy leaves of the African violet, for example, are quite resistant to dry air, but the flowers suffer.
For these reasons, it is always wise to increase humidity in the rooms where you grow houseplants. The most obvious way is to run a humidifier in the room. Or simply grow a lot of plants: since each plant gives off moisture, the more plants you have, the greater the atmospheric humidity.
Lowering the thermostat at night temporarily increases the ambient humidity and is also very effective. Or grow your plants in a naturally humid room, such as a laundry room (assuming that there is some sunlight!).
To maintain high humidity at all times for the most sensitive plants, place them in a terrarium… or in a clear plastic bag. They will remain in superb condition throughout the winter: humidity in a terrarium or a closed bag is as high as in a jungle and plants simply adore it!
On the contrary, spraying plants manually with water, typically with a recycled Windex bottle, is a total waste of time, even if you see it frequently recommended. The effect only lasts a few minutes, plus it stains the leaves. Try anything else but this!
So there you go, a few tips on how to keep your plants happy during the heating season. Put them into practice and you will soon have a real jungle of thriving foliage in your home!
This text was first published on this blog on December 10, 2014. It has been revised and the layout updated.