Houseplant Care in Winter: Light, Water and Dry Air

Why winter is different

University of Vermont Extension says the shorter, weaker daylight sends most houseplants into a resting state called quiescence: growth slows a great deal, and some plants, such as alocasias and caladiums, may lose their leaves. That is normal, and they should rebound in spring. Oregon State says water and fertilizer needs are generally lower in winter as a result.

Holiday plants have their own routines, on their own pages: poinsettia, Christmas cactus, amaryllis and paperwhites. If you have pets, see holiday plants and pets.

Water less, and check first

• Wait until it is dry. Vermont’s Master Gardener volunteer Judy Mirro says we tend to over-love our plants with too much water, especially in winter; hold off until the potting mix is truly dry. NC State says most indoor plants do best when the soil nearly dries out between waterings.
• Check below the surface. Kentucky says the surface dries quickly and is no guide: push a finger 1 to 2 inches in, water if it is dry there, and if not check again in a few days. NC State uses the top 2 inches, or the weight of the pot; Vermont uses a moisture meter, or a chopstick pushed into the mix.
• Cacti and succulents need only occasional water; Kentucky says every two to three weeks may be enough.
• Read the leaves. Kentucky says yellowing and dropping leaves often mean overwatering, which can rot the roots; rapid leaf drop may mean the plant is thirsty.

Find the light

NC State says light is the greatest limiting factor in winter: north- and east-facing windows that gave good indirect light in summer can become too shady. Move plants to a sunnier spot or add grow lights. Kentucky points to a south- or west-facing window, but not so close that the plant sits in a draft.

Raise the humidity

NC State says indoor humidity can fall below 20% in winter, while most houseplants prefer 40 to 50%. Kentucky says heated houses run 10 to 20% lower. Tropical plants suffer most (Vermont).

• Group plants together. They give off moisture from their leaves, and a cluster shares it (Kentucky, NC State).
• Use the bathroom or kitchen, the most humid rooms, if they have enough light (Kentucky).
• Set pots on a pebble tray filled with water, raised on the stones so the pot bottoms stay out of the water (Kentucky).
• Run a humidifier near the plants (Vermont, NC State, Kentucky).

Keep them out of drafts and away from heat

Vermont says to keep plants away from woodstoves and heating vents, out of drafty spots and not too close to windows, because houseplants do best with steady conditions. NC State says the same of drafty windows and dry, hot air from vents.

No fertilizer, no repotting

Vermont says hold off on fertilizing and transplanting in winter unless absolutely necessary, and wait until spring to renovate plants. NC State says resume fertilizing in March or April; Kentucky says when new growth appears in early spring.

Clean the leaves and watch for pests

Dust cuts the light a leaf can use. Vermont says wipe leaves with a damp cloth or give the plant a gentle, lukewarm shower and let all the water drain; NC State uses a very mild soap solution; University of Minnesota Extension says plain water and a soft cloth.

Cleaning is the time to look for pests. Vermont says spider mites thrive in winter’s low humidity and fungus gnats come with overwatering; look for webbing, sticky honeydew from aphids, white cottony mealybugs and bumps on stems that may be scale, and use yellow sticky traps to watch for gnats. Clemson lists the same pests and says they often follow overwatering.

Common mistakes

• Watering on a schedule. Check the mix first; winter plants use far less (Vermont, Kentucky).
• Trusting the soil surface. It dries first; check 1 to 2 inches down (Kentucky).
• Leaving plants in last summer’s spot. A north or east window can be too dark in winter (NC State).
• Parking plants by a vent or stove. Dry heat and swings stress them (Vermont, NC State).
• Feeding or repotting in midwinter. Wait for spring growth (Vermont, Kentucky).
• Panicking when a resting plant drops leaves. Some do every winter (Vermont).

For the rest of the month’s jobs, outdoors as well as in, see December garden jobs by zone and January garden jobs by zone.