How to Help Your Houseplants This Winter

When it comes to houseplants and the people who grow them, there’s not much to love about winter. The days are short, cold, and often gray, temperatures plunge during the long nights, and dry heat from furnaces and fireplaces sucks moisture from the air.

However, there are ways to show houseplants the love they need to survive and even thrive during these problematic growing months.

Basic Plant Maintenance

The first step to winter plant maintenance is to be aware of the greatest dangers your houseplants face. Those dangers are "the classic combo of low light, low humidity, and temperature extremes," said Becky Brinkman, manager of the Fuqua Orchid Center at the Atlanta Botanical Garden. "The remedy," she said, is the real estate mantra of "location, location, location—and some attention."

Another way to show houseplants some winter love is to avoid the three most common mistakes Brinkman says home growers make when caring for houseplants in winter:

• Leaving tropical plants on an unheated porch or garage or too close to a hot and dry air source
• Putting them too far away from a direct source of natural light
• Forgetting to check them for water

Avoid these mistakes with our top tips for winter houseplant care, courtesy of Brinkman and some members of the houseplant forum of the National Gardening Association.

Know the Temperature of Your Location

Buy a thermometer and hang it near your plants. For tropicals, the ideal night minimum temperature should be no lower than 58 degrees F (14.4 degrees C), and the daytime maximum temperature no higher than 75 degrees F (23.9 degrees C).

Choose a Location With Good Natural Light

Small plants can be placed on the windowsill—just make sure the leaves don’t touch the glass. If your windows leak cold air, caulk them or move the plant away from the glass to avoid cold drafts.

Check for Watering Needs at Least Every Other Day

As the surface of the soil dries, it will become lighter in color. Use your index finger to check the soil for moisture. Water when the top three-quarters of an inch of the soil feels dry.

Don't Use a Garage for Tropical Plants

"True tropicals, the ones from lowland moist tropics, need year-round warm and moist growing conditions," said Brinkman. "In nature, they never experience an extended cool dry rest or light deprivation. Three months in an unheated dark garage could likely produce an irreversible setback. Bring them indoors! Even a dry indoor climate is definitely better than an unheated dark garage."

Give Plants Less Fertilizer

With the decrease in day length and the house being cooler in winter than in summer, plant growth slows down. Some plants, such as succulents, may even go into a state of dormancy or partial dormancy. With slower growth, plants need fewer nutrients than during periods of continued growth.

As a result, you can cut fertilizing in half from the recommendations on the container's label. "We cut the dosage and frequency in half in our greenhouses in winter, from 200 to 100 ppm and from twice a month to once a month," Brinkman said.

Know Your Indoor Humidity

Ideally, the humidity in your home—the amount of moisture in the air—should be between 30 and 50%, according to the Environmental Protection Agency (EPA). Humidity that's too low or too high can cause health problems for you and issues for your furniture and the home itself.

One way to test home humidity is with a hygrometer, a device that looks like a thermometer and can be purchased at a hardware store. If the humidity in your home is less than 50%, Brinkman suggests choosing plants that have thick waxy leaves and avoiding thin-leaved plants.

"Many digital home thermostats installed in the last five years have a humidity sensor and the percent of relative humidity appears on the screen along with the temperature," said Brinkman. Relative humidity is the ratio of the actual amount of water vapor present in a volume of air at a given temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage, according to How Stuff Works.

"Humidity sensors are far more accurate than they were 10 years ago, so you may not need a hygrometer," Brinkman continued. "The maximum relative humidity houseplants can tolerate is 80%, but most people would find that intolerable in their homes. If you've created an enclosed microclimate for your plants, like a terrarium, remember to ventilate it occasionally to control humidity and allow CO2 inside."

Raise Humidity if Needed

To do this, you can:

Put Plants on a Saucer With Pebbles and Water

Just be sure the level of the water is below the top of the pebbles. If the bottom of the pot touches the water, it can wick the water up into the pot, which can cause root rot. This technique will raise the humidity around the plant but not in a larger area, such as the room where the plant is growing.

Mist Your Plants

Do mist, but also be aware that this comes with a caveat. "I'm often asked about misting with a hand spritzer," said Brinkman. "Misting doesn't hurt, but it’s not really effective either. The effect is too localized and too temporary. Instead, consider a humidifier to raise the humidity."

Invest in a High-Tech Humidifier

Consider choosing a humidifier with a built-in hygrometer that maintains humidity within a healthy range.

Group Plants

Plants growing in a "community" will naturally raise the humidity around them.

Dust Your Plants

Left alone, dust can collect on leaves and reduce the amount of moisture the leaves absorb. Simply dip a soft cloth in water and wipe down the leaves.

Check for Spider Mites

You can do this while dusting your plants. These pests thrive and reproduce rapidly in warm, dry air, which is why winter is the season you're more likely to find them. Look for tiny dust-like particles on the tops and bottoms of leaves. If you detect an infestation, take the plants to a sink and spray them with a stream of water to knock the mites from the leaves. If the infestation persists, spray the plants with insecticidal soap or horticultural oil, being sure to thoroughly cover the top and undersides of the leaves. Proper watering will help reduce pest infestations.

Run a Small Fan Near Your Plants

The air circulation is good for them. Think of it this way: Don’t you enjoy a gentle breeze on a warm day?

Don't Re-Pot During the Winter

Wait until spring, unless the plant is so pot-bound it's becoming obviously stressed. If you must re-pot, avoid over-potting (using a bigger pot than necessary). Choose a pot that is slightly bigger than the root ball rather than using a pot you think is in proportion to the leaf mass.

When spring does return (and it will!), here’s a final tip for any houseplants you might move outside in the spring and not bring back indoors until temperatures drop again in the fall. Move them gradually in steps into their ideal light conditions. Moving plants from the low-light conditions of most homes directly into the brightest light they can tolerate may result in sunburn—black spots—on the leaves. That sunburn will not go away. Instead, it will serve as a lasting reminder not to make this mistake again.