How to keep your houseplants (and yourself) less miserable this winter

A very basic guide to indoor winter gardening, according to experts.

Winter will suck. We gathered some of Vox’s coziest minds to help you make it suck less.

So you’ve acquired a houseplant during the Covid-19 pandemic. Or several. Or dozens.

You’re certainly not alone. Next to cultivating sourdough, gardening has become one of the most popular Covid-19 pandemic hobbies across the United States as people spend more time at home, overwhelming plant nurseries that are still trying to maintain social distancing precautions.

“I can tell you that we have seen worldwide interest in gardening that has approximately doubled in terms of individual participation from 2019 to 2020,” said Dave Whitinger, executive director of the National Gardening Association, in an email. “The number of website visitors to garden.org is twice as high as last year, and most of the gardening companies we have spoken with have reported approximately the same thing. The gardening companies I have spoken to have all told me they have completely sold out their inventory this year.”

With so many restrictions on going outside, it seems natural to want to bring some of the outdoors inside (or at least close by). Plants bring us numerous benefits. Beyond the obvious aesthetics, your pothos plants, African violets, and succulents can relieve stress and boost productivity. (Their air-cleaning benefits, however, are a bit more questionable.)

But now as we head into the winter, when cooler outdoor air becomes less hospitable to fingers and fronds alike, first-time gardeners are facing the challenge of nurturing their new charges through one of the toughest times of year.

To find out more, I called up experts at the United States Botanic Garden in Washington, DC. It’s the oldest continuously operating botanic garden in the US and turns 200 this year. It contains nearly 29,000 square feet of indoor growing space, in addition to five acres of outdoor gardens. Its 65,000-plant collection includes chocolate plants, orchids, the endangered aloalo flower, and the crown jewels, two 8-foot-tall flowers that look like deformed penises and smell like rotting corpses. I figured they would know a thing or two about keeping fussy plants alive.

Whether your thumbs are barely turning green or you’re an aspiring plantfluencer, here’s what to know about keeping your plants (and maybe yourself) happy and healthy through the cold months.

Plants can prepare for winter, but they may need your help

The first step in getting your household foliage to survive the winter is to do some homework. That can involve doing some research in a plant database to learn more about the ideal conditions for your plant, like temperatures, sunlight, and soil. You can also look up the US Department of Agriculture hardiness zone you live in, which can help determine which of your plants can survive the winter outdoors and which need the warmth of your home.

“Getting a little bit of background of the plants is probably one of the most critical things for winter care,” said Angela Weber-Hetrick, the gardens and grounds supervisor at the US Botanic Garden. “Tropical needs are a lot different than your hardy plants, or Zone 7a, which is what we are here in the DC area.”

Plants themselves are quite varied, so it’s difficult to come up with broad recommendations for every bit of greenery. Weber-Hetrick explained that there are plants that do winter prep of their own. Many plants, but particularly perennials that experience winters in the wild, can go dormant when the season changes. That’s when the plant stops growing actively. Its leaves and stems may even fall off, but the root structure is still alive. (A general way to test whether a plant is alive is to bend the stem. If it’s pliable, it’s alive, but if it’s brittle, it’s probably dead.)

Devin Dotson/US Botanic Garden

The signs of dormancy can be subtle in houseplants. It can be as simple as their growth slowing. But not every piece of vegetation hunkers down for the season. Succulents like aloe go dormant in the summer while other succulents like agave go dormant in the winter, for example.

When it comes to plants that go dormant in the winter, it’s all the more critical for them to be at their healthiest as the days get shorter.

“In fall, they’re starting to store up all their carbohydrates, and really what they are trying to do is basically store as much energy as they can to make it through the winter,” Weber-Hetrick said.

Tropical plants, like philodendron, cane, and bamboo, also respond to shorter days with less growth, thereby consuming less water and fertilizer. And other species may need some trimming to get rid of dead branches or decaying leaves. “Sometimes it needs a good pruning, a good haircut, before going into the winter months,” Weber-Hetrick said.

But regardless of the species, once winter begins, you, the plant owner, become the gatekeeper for almost everything that a plant needs to survive if it’s kept indoors. So it’s on you to figure out what your garden needs.

Keep a close eye on your greenery and establish a routine

Every home has its own terroir, and general plant care guidelines may be too vague for your porch, windowsill, or hanging basket. That’s why your own observations are crucial.

“You can kind of ‘listen to your plants’ in terms of just kind of looking at them,” said Chelsea McKinley, a plant health specialist at the US Botanic Garden. “If it seems like they’re drying out more frequently and they’re putting out more growth, then that’s a sign that they’re ready for more water and maybe for some light fertilizing.”

Throughout the winter, here are some of the key things to observe on roots, stems, leaves, and buds to help your plants thrive.

Pests: Make sure there aren’t any stowaways on plants you bring inside, and keep an eye out for any critters that could harm them, like aphids and mealybugs. Check the undersides of leaves for even tinier pests like spider mites. “They usually cause a silvering or yellowing of the leaves,” McKinley said. “Those you might need a magnifying glass to see.”

If you are repotting or moving plants to a different container, make sure the new vessel is sterile. Use a mild bleach solution and rinse thoroughly to prevent bacterial or fungal infections.

Light: Plants depend on photosynthesis, the process by which they use light, carbon dioxide, and water to make sugar and oxygen. With the sun going down earlier, every photon is precious. Some plants can cope with less light, but others may need the assistance of a growing lamp. Check to make sure what kind of lighting your plant needs and ensure your lighting source is adequate, especially if it’s a supplemental source. “You just want to make sure that lightbulb is fairly bright and has both red and blue wavelengths in the spectrum,” McKinley said. If you are just relying on sunlight, the optimal position can change through the winter, so be prepared to move your plants.

Devin Dotson/US Botanic Garden

Temperature: As it gets cold outside, it becomes more important to maintain warmth inside. Though some plants like orchids prefer a bit of a nighttime drop in temperature, most prefer steady conditions, so avoid placing them in drafty areas.

Water: Both too much and too little water can be harmful. That can manifest as wilting or yellowing leaves. But rather than waiting for a plant to show signs of distress, one sign that a plant may be ready to water is if the top centimeter or two of soil is dry.

“When you do water, make sure the entire root bulb gets really wet,” McKinley said. “You want about 10 percent of the water you put into the pot to come out the bottom of the pot.” This helps flush out salt in the root structure. But make sure the water drains away and that the plant doesn’t remain sitting in water.

Some chemicals in tap water can also be harmful to plants, leading to problems like yellowing leaves. You can use distilled water or leave some water out for 24 hours to allow residual chlorine to evaporate out.

Humidity: Running the furnace in the winter can dry out the air in your home. And as dry, heated air parches your throat, it can desiccate plants as well. A humidifier can help reduce these effects. So can misting plants with a spray bottle. Maintaining proper humidity can also reduce the need for watering. But make sure to wipe down leaves after misting since tap water can leave behind mineral deposits as it evaporates. A wipe will also remove household dust that can block sunlight.

Balancing all of these elements may be tricky at first, but over time, it should get easier to establish a plant care rhythm and routine. “Plants love consistency,” Weber-Hetrick said.

If you’re looking for inspiration, you can also explore the US Botanic Garden virtually. And while we’re all housebound this winter with our aloes, begonias, and cacti, know that it’s totally okay to talk to your plants; just be cautious if they start talking back.