Your houseplants aren't immune to life-threatening challenges during the winter, even though they live in a temperature-controlled climate. Indoor plants, whether they are year-round houseplants or plants you brought indoors to over-winter, can be affected by factors such as temperatures that fluctuate from daytime heat to evening chill, dry air, short days, and limited light. Keep your houseplants thriving by modifying their care during the cooler months of the year.
Adjust Your Watering Routine
It might sound counterintuitive, but indoor plants need less water during the winter. While it's true that winter air is drier, plants experience a slower rate of growth during colder months; some even go completely dormant. Therefore, plants need less water to keep hydrated, and overwatering can lead to root rot. Keep in mind that different plants have different water needs—drought-tolerant cacti and other succulents might not need watering at all.
Surface soil can dry out more quickly during winter months, but that's not a good indicator that the plant needs water. Push your finger into the soil to determine if it is dry an inch or two below the surface—that's when it's time to bring out the watering can.
Do not use cold water to water your houseplants. Use water that is about room temperature to avoid shocking the plant's roots.
Alter Humidity Levels
Low humidity levels can be the biggest hurdle that houseplants must overcome during winter. The humidity level in heated homes can drop to 10 to 20 percent in winter, and plants prefer a level closer to 50 percent. If you have a humidifier in your home, move your plants to a spot where they will enjoy its benefits. If you do not have a humidifier, raise the humidity level by other means.
Start by clustering your plants in groups. Plants naturally release water through their leaves by transpiring, so grouping them together will put that moisture to good use. Bathrooms and kitchens are the best rooms to congregate your plants because they accumulate the most moisture from showers and boiling water.
Another good option is the old trick of placing your plants on or near a tray of water. But, don't let the plants sit directly in water. Place pebbles or stones in the tray to raise the bottom of the pots above the water level in the tray and place the pots on top of the stones.
Misting tends to be better at making a gardener feel good about themselves rather than benefiting the plants. You might think you are giving your plants some relief, but misting is only a temporary blast of moisture. To be effective you would need to mist multiple times a day to really see any benefit because indoor temperatures will evaporate moisture quickly. If you have only a couple of plants and you think you will be very conscientious about misting, give it a try. It's hard to over-mist an indoor plant. During humid summers, misting plants can lead to fungal problems, but that should not be a problem during winter.
Pay Attention to Temperature
Most plants, like people, are comfortable in daytime temperatures between 65 to 75 degrees Fahrenheit and nighttime temps above 50 degrees Fahrenheit. To provide that for your plants, keep them away from both cold drafts and sources of heat such as radiators, ovens, fireplaces, and electronic devices. Fluctuations in temperature can kill houseplants just as easily as prolonged periods of heat or cold.
Follow the Sun
Not only are there fewer hours of sunlight during winter, but the rays also come in at a lower angle. You might need to relocate your houseplants to a brighter spot or even add supplemental light. A good spot is a south- or west-facing window that remains sunny all day. However, don't move plants too close to a frosty window because they might get a draft.
Rotate the pots about a 1/4 turn whenever you water your plants. This ensures that all sides of the plant receive some sun and grow evenly, rather than some branches stretching to reach the light.
Put Your Houseplants on a Diet
Because your plants are not actively growing, they don't need any fertilizer. Feeding them now will just upset their natural cycle, so stop feeding until early spring. When you start to see signs of new growth or the existing leaves appear to be greening up, resume fertilizing to give them a boost for the growing season.
Give your houseplants the essentials to sustain them through winter, but don't fuss over them or kill them with kindness. Keep an eye out for early signs of problems, which can still include insect pests, even in winter. However, wait until the growing season resumes before you re-pot them or start taking cuttings. Consider winter an offseason for your houseplants and let them rest.
Winter Care for Houseplants. University of Nebraska-Lincoln Extension Website