Through winter’s brief, dim days, houseplants often live near windows.
“Glass gets cold, though. So, any plants touching a window or patio door are likely to become damaged. Plus, cold glass causes heat loss from nearby objects indoors – especially at night. Windows and doors can also leak air in from the outdoors. Cold drafts can damage houseplants, too,” said Ward Upham, horticulturist with Kansas State University Research and Extension.
At the same time, plants’ placement near a room’s “outside” wall can put them on or close to a heat register, Upham said. If so, hot air will become a worse hazard, literally drying the plants’ greens.
Many houseplants – especially those grown for foliage – are natives of the subtropics or tropics, he explained. They’re fine at human comfort levels. But, they start to look sickly at less than 50 degrees.
“You’ll need to monitor winter’s air temperatures for houseplants you’re exposing to sunlight,” Upham said. “They may need to move a little further from a patio door. Or, you may have to close the drapes or pull down the shade between your plants and a cold window at night.”
A few houseplants require extra warmth. The diva of this “sensitive” group is the false aralia (Schefflera, formerly Dizygotheca). A tree-shaped tropical with slender, jagged leaflets arranged like fingers, false aralia can look a bit like a tough marijuana plant. But, it needs temperatures of at least 65 F.
Upham said other “sensitives” – all of which require temperatures of 60 degrees or above – are:
* Chinese evergreen (Algaonema) – clumping plant with long, pointed, variegated leaves.
* Flamingo flower (Anthurium) – exotic with heart-shaped, waxy “flowers” and a yellow spike.
* Croton (Codiaeum) – leathery foliage known for wildly brilliant colors and varied leaf shapes.
* Balfour and Ming aralia (Polyscias) – upright, rather columnar Oriental trees with twisted stems and attractive leaves. Foliage can range from deeply veined and “ruffly” to lacy and delicately bushy.