Each season comes with its own set of charms and challenges for plants—perhaps more of the latter for houseplants over winter. Houseplants typically originate from a climate that's hot and humid year-round, meaning they're unaccustomed to winter's short days and the dry heated air of Canadian homes. The good news, though, is that by tweaking your usual care routine, houseplants can make it through the heating season with flying colours.
Pull off dead, yellowed or damaged leaves and trim away weak growth. Then give plants a shower to remove dust and dirt; this lets more light onto the leaf's surface—greatly appreciated by plants in the dark, dull days of winter.
If plants seem to dry out as fast as you can water them, repot your plants into slightly larger quarters. Cut off any dead roots, and, only if several smaller roots are present, those thick taproots that run around the insides of pots. These taproots help anchor plants in the ground outdoors but are useless in a pot. By removing them, you encourage a proliferation of small roots, which are much better at absorbing water and nutrients.
Drier than the Sahara
Heated air is dry air. During winter, the relative humidity in the average home plummets to about 15 per cent. Compare that with the Sahara Desert, where it's about 25 per cent. In practical terms, this means houseplants will release vapour through transpiration as fast as they can absorb water, sometimes even faster, resulting in leaves that are wilted, curled under or have brown tips. And flower buds may dry up before you even see them, partly explaining the paucity of blooms during winter months. You've got to either raise the humidity level or grow plants that cope well with dry air, such as cacti and succulents.
Consider acquiring a room or home humidifier to raise the humidity level to a comfortable 50 per cent or so, which is also beneficial for people and wooden furniture. Some plants prefer 60, or even 70, per cent humidity, similar to what they experience in summer. But since that much moisture can lead to condensation and a general feeling of dankness, create instead an extra-humid microclimate for the neediest plants, the ones with thin leaves. Group plants together, placing those with thin leaves in the centre. Several plants transpiring together can create considerable humidity. If that isn't enough, build a humidity tray: Fill a waterproof tray with gravel, pour water into the bottom and set plants on top. Refill the tray frequently but lightly, making sure you're not leaving a pool of water above the gravel. Plants left sitting in water may develop root rot.
Keep in mind that most houseplants are happy with the warm air temperatures during the day and lower ones, such as 18°C, at night. For plants that prefer cool winter conditions (gardenias, cyclamen and most cacti, for example), seek out a room that you keep cooler than others but still above freezing—a spare bedroom, perhaps. Keep all plants out of cold drafts and blasts of heat.
Photo: Clivia miniata. Photography by Michael Davis