Coming in from the cold

Experts share tips for keeping plants alive, healthy indoors for the winter

By: Brian Louwers | Metro | Published October 13, 2021

 Summer bulbs from some plants, including canna lilies, can be dug up and cleaned in the fall, kept dry, and stored over winter for planting next spring.

Summer bulbs from some plants, including canna lilies, can be dug up and cleaned in the fall, kept dry, and stored over winter for planting next spring.

Photo provided by Lori Imboden

METRO DETROIT — It’s tough to let go of the plants that you’ve grown to know and love over Michigan’s sweet summer months, and you don’t always have to.

“There could be two different scenarios,” said Lori Imboden, consumer horticulture supervising educator for the Michigan State University Extension-Oakland County. “You could have an indoor plant that’s a tropical plant that you took outside for the summer, so if you bring that back inside, that probably has a pretty good chance of readapting to the indoors, if it was doing well indoors otherwise. The other thing people sometimes try to do is, annuals they purchased indoors, they’ll try to overwinter them to save them for next year.

“Some of those do OK inside. Some of them don’t,” Imboden said. “It really kind of depends on how much light you have for them. Every time you go in and out, you have that chance of bringing in pests.”

Imboden said the Extension office sometimes takes questions from people looking to save summer bulbs from plants like gladiolus, canna lilies and dahlias.

“Those can be brought in over the winter and stored,” Imboden said. “Dahlias, I think people just hose those off. Gladiolus, you need to brush them off and then sort of cure them, which means just leaving them in a cool place that’s not in the sun.”

She said most summer bulbs need to sit for a few days at least, and gladiolus take a bit longer.

“Store them in a cool, dry place over the winter, and then those can be planted out the next year,” Imboden said. “Those will multiply over the summer, so if you started off with one canna, you can end up with a lot of cannas if you save them every year.”

To save the summer bulbs, cut the foliage back once it dies. Dig up the bulbs after the first light frost and clean them off, but don’t wait until after a hard freeze.

Imboden said the bulbs will need to be clean and dry when they’re stored. You won’t need to store them with soil or any kind of potting media.

“That’s a pretty common thing to do and relatively easy, because you’re less likely to bring in pests,” she said. “Once they’re stored, really, you just want to check on them periodically to make sure nothing’s rotting or drying out. You don’t have to do anything all winter.”

Of course, all plants are meant to be outdoors somewhere, but some just can’t survive through a Michigan winter.

For plants returning to the cozy confines of your home after a summer on a porch or patio, Imboden said there are a few things to keep in mind.

“One is that, outside, they’d probably be getting more light than they would indoors,” Imboden said. “Also, the days will be shorter and the plants won’t be growing as much, so it’s going to be a little easier to overwater them indoors.

“Just like in the spring when you first take things out and sort of ease them into it by exposing them to a little more light each day for a while, you’re also going to want to kind of ease them into coming indoors,” Imboden said. “If you take them from a bright sunny place and stick them in a cold, dark corner inside, they’re going to stop growing and you may end up with some root rot and some things like that, especially if they were wet when you brought them in.”

Aside from helping the plant adapt to the changing conditions, you’ll want to make sure the plant is the only thing you’re bringing back indoors.   

“If people are bringing things from the outside to the inside, especially if they have other indoor plants, they don’t want to bring any pests indoors,” Imboden said.

She suggests doing a thorough physical inspection of the plant to check for any visible signs of insects.

“And then, ideally, and I realize not everyone has the space for it, you would have those plants quarantined from your other plants, just like you would if you bought a brand new plant,” Imboden said. “In an ideal world, it would be four to six weeks, to see if any eggs are going to hatch, anything like that.

“If you did bring in some little friend from outside, you don’t want it to spread to your other plants. That’s always the complication of bringing things in and out. Sometimes, you bring things back in,” Imboden said.

She added, “Just in general, a lot of times, you’re bringing things in, and it’s a live plant, it may not thrive over the winter, but you can sort of keep things alive. The conditions are just really different. A lot less light, a lot drier. Some things take to that better than others.”

The MSU Extension offers many resources for homeowners and gardeners, including those looking to help transition plants from outdoor to indoor environments.

An article written in December 2020 by Christopher Imler, horticulture and veterans liaison extension educator with the Kalamazoo County Extension office, and Sarah Rautio, MSU Extension master gardener state leader, offers tips on the year-round cultivation of tropical and tender perennial plants.

While they said the plants can add an “exotic flair to a northern home, drawing a visitor’s eye to lush foliage and unusual shapes,” the article noted that gardeners must assess temperature, pests, lighting and fertilization/watering issues.

Plant “hardiness” to cold temperatures is addressed, and gardeners are advised to bring tropical and cold-sensitive species inside well in advance of the first frost.

“While many plants can survive sustained temperatures below 50°F, relocating them indoors before temperatures drop below 60°F during the day will help reduce any stress from sudden temperature changes,” the authors wrote.

Mid-September has been mentioned in other Extension bulletins as the time to move plants indoors after a thorough inspection for pests, and the article by Imler and Rautio said Michigan’s varied climate across the state lends itself to no firm guideline.

Rather, they advise monitoring the forecast to track temperatures and mitigate risk to sensitive plants.

In the spring, those plants should, of course, remain indoors until the risk of frost is over.

Much more information is available through the MSU Extension at canr.msu.edu/news/overwintering-container-plants.