Moving houseplants indoors with the onset of cold weather is not your typical furniture-shifting exercise. It requires planning, since houseplants for the most part are tender tropicals and need time to acclimate to a changed growing environment.
“Bring them in over a two-week period,” said Kate Karam, editorial director for Monrovia Nursery Co. in Azuza, California. “Some people move them from full sun to full shade [outdoors] to simulate the reduction in indoor lighting. I bring mine in at night and take them out again in the morning. And then eventually I just keep them in.”
Houseplants freak out if you simply run them inside and plunk them down on a windowsill, she said. Such haste frequently results in plant shock and leaf drop.
“A little bit of patience will save you a lot of heartbreak,” Karam said.
Check closely for such leaf-sucking pests as aphids, mealy bugs and spider mites. Deal with them outdoors if the plants are infested.
“I hose them [plants] down and then give them a good treatment of neem oil,” Karam said. Neem oil is an organic pesticide, a byproduct of seeds from the neem tree.
“It’s good at killing things that crawl,” she said. “Use it at half strength from a spray bottle. It’s a helpful thing to have in your arsenal for houseplants.”
Quarantine houseplants for a time after bringing them indoors, said Diana Alfuth, an Extension horticulture educator with the University of Wisconsin-Madison.
“Sitting outside, there may be all kinds of things living in them,” Alfuth said. “One year I brought in my plants and very shortly found a little frog hopping across my dining room floor.”
Indoor gardening with tropicals like hibiscus, bougainvillea, mandevilla and palms can get complicated. Tasks to manage include lighting, water, temperature, humidity and nutrition, and they’re all inter-related.
“Lighting and watering are the most important,” Alfuth said. “Watering is related to how much light there is.”
Try placing houseplants in the sunniest areas of the house. Windows filter out the sun, somewhat hampering photosynthesis, the process that creates the sugars and carbohydrates needed for plants to grow.
It also gets cloudier in winter, so consider taking measures to elevate light levels. Keep the windows clean, remove the screens and add supplemental lighting.
Overwatering houseplants is one of the most common mistakes in gardening. It suffocates the roots and allows root fungi to settle in, Alfuth said.
Water only when the plants need it. “Dig your finger into the surface of the soil and if it’s dry one-half inch deep, then it’s time to water,” she said.
Bring plants indoors to avoid chill injury when overnight lows dip consistently into the mid-40s. Most houseplants prefer days between 65 and 75 degrees, with nights about 10 degrees colder, Alfuth said.
Keep plants away from heat vents and out of entryways where drafts can become too dry or too cold.
“There’s little active growth in most houseplants in winter so they don’t need any fertilizer,” said David Trinklein, an Extension horticulturist with the University of Missouri.
“In most cases, overwintering tropical plants not only saves money but also results in larger, more impressive plants the next year,” Trinklein said.